content: {-# LANGUAGE CPP, RecordWildCards, NamedFieldPuns, RankNTypes #-}
  {-# LANGUAGE ViewPatterns #-}
  {-# LANGUAGE TypeFamilies #-}
  {-# LANGUAGE NoMonoLocalBinds #-}
  {-# LANGUAGE DeriveDataTypeable #-}
  {-# LANGUAGE DeriveFunctor #-}
  
  -- | Planning how to build everything in a project.
  --
  module Distribution.Client.ProjectPlanning (
      -- * elaborated install plan types
      ElaboratedInstallPlan,
      ElaboratedConfiguredPackage(..),
      ElaboratedPlanPackage,
      ElaboratedSharedConfig(..),
      ElaboratedReadyPackage,
      BuildStyle(..),
      CabalFileText,
  
      -- * Producing the elaborated install plan
      rebuildProjectConfig,
      rebuildInstallPlan,
  
      -- * Build targets
      availableTargets,
      AvailableTarget(..),
      AvailableTargetStatus(..),
      TargetRequested(..),
      ComponentTarget(..),
      SubComponentTarget(..),
      showComponentTarget,
      nubComponentTargets,
  
      -- * Selecting a plan subset
      pruneInstallPlanToTargets,
      TargetAction(..),
      pruneInstallPlanToDependencies,
      CannotPruneDependencies(..),
  
      -- * Utils required for building
      pkgHasEphemeralBuildTargets,
      elabBuildTargetWholeComponents,
  
      -- * Setup.hs CLI flags for building
      setupHsScriptOptions,
      setupHsConfigureFlags,
      setupHsConfigureArgs,
      setupHsBuildFlags,
      setupHsBuildArgs,
      setupHsReplFlags,
      setupHsReplArgs,
      setupHsTestFlags,
      setupHsTestArgs,
      setupHsBenchFlags,
      setupHsBenchArgs,
      setupHsCopyFlags,
      setupHsRegisterFlags,
      setupHsHaddockFlags,
  
      packageHashInputs,
  
      -- * Path construction
      binDirectoryFor,
      binDirectories
    ) where
  
  import Prelude ()
  import Distribution.Client.Compat.Prelude
  
  import           Distribution.Client.ProjectPlanning.Types as Ty
  import           Distribution.Client.PackageHash
  import           Distribution.Client.RebuildMonad
  import           Distribution.Client.Store
  import           Distribution.Client.ProjectConfig
  import           Distribution.Client.ProjectPlanOutput
  
  import           Distribution.Client.Types
  import qualified Distribution.Client.InstallPlan as InstallPlan
  import qualified Distribution.Client.SolverInstallPlan as SolverInstallPlan
  import           Distribution.Client.Dependency
  import           Distribution.Client.Dependency.Types
  import qualified Distribution.Client.IndexUtils as IndexUtils
  import           Distribution.Client.Targets (userToPackageConstraint)
  import           Distribution.Client.DistDirLayout
  import           Distribution.Client.SetupWrapper
  import           Distribution.Client.JobControl
  import           Distribution.Client.BinaryUtils
  import           Distribution.Client.FetchUtils
  import qualified Hackage.Security.Client as Sec
  import           Distribution.Client.Setup hiding (packageName, cabalVersion)
  import           Distribution.Utils.NubList
  import           Distribution.Utils.LogProgress
  import           Distribution.Utils.MapAccum
  
  import qualified Distribution.Solver.Types.ComponentDeps as CD
  import           Distribution.Solver.Types.ComponentDeps (ComponentDeps)
  import           Distribution.Solver.Types.ConstraintSource
  import           Distribution.Solver.Types.LabeledPackageConstraint
  import           Distribution.Solver.Types.OptionalStanza
  import           Distribution.Solver.Types.PkgConfigDb
  import           Distribution.Solver.Types.ResolverPackage
  import           Distribution.Solver.Types.SolverId
  import           Distribution.Solver.Types.SolverPackage
  import           Distribution.Solver.Types.InstSolverPackage
  import           Distribution.Solver.Types.SourcePackage
  import           Distribution.Solver.Types.Settings
  
  import           Distribution.ModuleName
  import           Distribution.Package hiding
    (InstalledPackageId, installedPackageId)
  import           Distribution.Types.AnnotatedId
  import           Distribution.Types.ComponentName
  import           Distribution.Types.Dependency
  import           Distribution.Types.PkgconfigDependency
  import           Distribution.Types.SourceRepo
  import           Distribution.Types.UnqualComponentName
  import           Distribution.System
  import qualified Distribution.PackageDescription as Cabal
  import qualified Distribution.PackageDescription as PD
  import qualified Distribution.PackageDescription.Configuration as PD
  import           Distribution.Simple.PackageIndex (InstalledPackageIndex)
  import           Distribution.Simple.Compiler hiding (Flag)
  import qualified Distribution.Simple.GHC   as GHC   --TODO: [code cleanup] eliminate
  import qualified Distribution.Simple.GHCJS as GHCJS --TODO: [code cleanup] eliminate
  import qualified Distribution.Simple.Eta   as Eta   --TODO: [code cleanup] eliminate
  import           Distribution.Simple.Program
  import           Distribution.Simple.Program.Db
  import           Distribution.Simple.Program.Find
  import qualified Distribution.Simple.Setup as Cabal
  import           Distribution.Simple.Setup
    (Flag, toFlag, flagToMaybe, flagToList, fromFlagOrDefault)
  import qualified Distribution.Simple.Configure as Cabal
  import qualified Distribution.Simple.LocalBuildInfo as Cabal
  import           Distribution.Simple.LocalBuildInfo
                     ( Component(..), pkgComponents, componentBuildInfo
                     , componentName )
  import qualified Distribution.Simple.InstallDirs as InstallDirs
  import qualified Distribution.InstalledPackageInfo as IPI
  
  import           Distribution.Backpack.ConfiguredComponent
  import           Distribution.Backpack.LinkedComponent
  import           Distribution.Backpack.ComponentsGraph
  import           Distribution.Backpack.ModuleShape
  import           Distribution.Backpack.FullUnitId
  import           Distribution.Backpack
  import           Distribution.Types.ComponentInclude
  
  import           Distribution.Simple.Utils hiding (matchFileGlob)
  import           Distribution.Version
  import           Distribution.Verbosity
  import           Distribution.Text
  
  import qualified Distribution.Compat.Graph as Graph
  import           Distribution.Compat.Graph(IsNode(..))
  
  import           Text.PrettyPrint hiding ((<>))
  import qualified Text.PrettyPrint as Disp
  import qualified Data.Map as Map
  import           Data.Set (Set)
  import qualified Data.Set as Set
  import           Control.Monad
  import qualified Data.Traversable as T
  import           Control.Monad.State as State
  import           Control.Exception
  import           Data.List (groupBy)
  import           Data.Either
  import           Data.Function
  import           System.FilePath
  import           System.IO
  
  ------------------------------------------------------------------------------
  -- * Elaborated install plan
  ------------------------------------------------------------------------------
  
  -- "Elaborated" -- worked out with great care and nicety of detail;
  --                 executed with great minuteness: elaborate preparations;
  --                 elaborate care.
  --
  -- So here's the idea:
  --
  -- Rather than a miscellaneous collection of 'ConfigFlags', 'InstallFlags' etc
  -- all passed in as separate args and which are then further selected,
  -- transformed etc during the execution of the build. Instead we construct
  -- an elaborated install plan that includes everything we will need, and then
  -- during the execution of the plan we do as little transformation of this
  -- info as possible.
  --
  -- So we're trying to split the work into two phases: construction of the
  -- elaborated install plan (which as far as possible should be pure) and
  -- then simple execution of that plan without any smarts, just doing what the
  -- plan says to do.
  --
  -- So that means we need a representation of this fully elaborated install
  -- plan. The representation consists of two parts:
  --
  -- * A 'ElaboratedInstallPlan'. This is a 'GenericInstallPlan' with a
  --   representation of source packages that includes a lot more detail about
  --   that package's individual configuration
  --
  -- * A 'ElaboratedSharedConfig'. Some package configuration is the same for
  --   every package in a plan. Rather than duplicate that info every entry in
  --   the 'GenericInstallPlan' we keep that separately.
  --
  -- The division between the shared and per-package config is /not set in stone
  -- for all time/. For example if we wanted to generalise the install plan to
  -- describe a situation where we want to build some packages with GHC and some
  -- with GHCJS then the platform and compiler would no longer be shared between
  -- all packages but would have to be per-package (probably with some sanity
  -- condition on the graph structure).
  --
  
  -- Refer to ProjectPlanning.Types for details of these important types:
  
  -- type ElaboratedInstallPlan = ...
  -- type ElaboratedPlanPackage = ...
  -- data ElaboratedSharedConfig = ...
  -- data ElaboratedConfiguredPackage = ...
  -- data BuildStyle =
  
  
  -- | Check that an 'ElaboratedConfiguredPackage' actually makes
  -- sense under some 'ElaboratedSharedConfig'.
  sanityCheckElaboratedConfiguredPackage
      :: ElaboratedSharedConfig
      -> ElaboratedConfiguredPackage
      -> a
      -> a
  sanityCheckElaboratedConfiguredPackage sharedConfig
                               elab@ElaboratedConfiguredPackage{..} =
      (case elabPkgOrComp of
          ElabPackage pkg -> sanityCheckElaboratedPackage elab pkg
          ElabComponent comp -> sanityCheckElaboratedComponent elab comp)
  
      -- either a package is being built inplace, or the
      -- 'installedPackageId' we assigned is consistent with
      -- the 'hashedInstalledPackageId' we would compute from
      -- the elaborated configured package
    . assert (elabBuildStyle == BuildInplaceOnly ||
       elabComponentId == hashedInstalledPackageId
                              (packageHashInputs sharedConfig elab))
  
      -- the stanzas explicitly disabled should not be available
    . assert (Set.null (Map.keysSet (Map.filter not elabStanzasRequested)
                  `Set.intersection` elabStanzasAvailable))
  
      -- either a package is built inplace, or we are not attempting to
      -- build any test suites or benchmarks (we never build these
      -- for remote packages!)
    . assert (elabBuildStyle == BuildInplaceOnly ||
       Set.null elabStanzasAvailable)
  
  sanityCheckElaboratedComponent
      :: ElaboratedConfiguredPackage
      -> ElaboratedComponent
      -> a
      -> a
  sanityCheckElaboratedComponent ElaboratedConfiguredPackage{..}
                                 ElaboratedComponent{..} =
  
      -- Should not be building bench or test if not inplace.
      assert (elabBuildStyle == BuildInplaceOnly ||
       case compComponentName of
          Nothing              -> True
          Just CLibName        -> True
          Just (CSubLibName _) -> True
          Just (CExeName _)    -> True
          -- This is interesting: there's no way to declare a dependency
          -- on a foreign library at the moment, but you may still want
          -- to install these to the store
          Just (CFLibName _)   -> True
          Just (CBenchName _)  -> False
          Just (CTestName _)   -> False)
  
  
  sanityCheckElaboratedPackage
      :: ElaboratedConfiguredPackage
      -> ElaboratedPackage
      -> a
      -> a
  sanityCheckElaboratedPackage ElaboratedConfiguredPackage{..}
                               ElaboratedPackage{..} =
      -- we should only have enabled stanzas that actually can be built
      -- (according to the solver)
      assert (pkgStanzasEnabled `Set.isSubsetOf` elabStanzasAvailable)
  
      -- the stanzas that the user explicitly requested should be
      -- enabled (by the previous test, they are also available)
    . assert (Map.keysSet (Map.filter id elabStanzasRequested)
                  `Set.isSubsetOf` pkgStanzasEnabled)
  
  ------------------------------------------------------------------------------
  -- * Deciding what to do: making an 'ElaboratedInstallPlan'
  ------------------------------------------------------------------------------
  
  -- | Return the up-to-date project config and information about the local
  -- packages within the project.
  --
  rebuildProjectConfig :: Verbosity
                       -> DistDirLayout
                       -> ProjectConfig
                       -> IO (ProjectConfig,
                              [PackageSpecifier UnresolvedSourcePackage])
  rebuildProjectConfig verbosity
                       distDirLayout@DistDirLayout {
                         distProjectRootDirectory,
                         distDirectory,
                         distProjectCacheFile,
                         distProjectCacheDirectory
                       }
                       cliConfig = do
  
      (projectConfig, localPackages) <-
        runRebuild distProjectRootDirectory $
        rerunIfChanged verbosity fileMonitorProjectConfig () $ do
  
          projectConfig <- phaseReadProjectConfig
          localPackages <- phaseReadLocalPackages projectConfig
          return (projectConfig, localPackages)
  
      return (projectConfig <> cliConfig, localPackages)
  
    where
      ProjectConfigShared {
        projectConfigConfigFile
      } = projectConfigShared cliConfig
  
      ProjectConfigBuildOnly {
        projectConfigSendMetrics
      } = projectConfigBuildOnly cliConfig
  
      fileMonitorProjectConfig = newFileMonitor (distProjectCacheFile "config")
  
      -- Read the cabal.project (or implicit config) and combine it with
      -- arguments from the command line
      --
      phaseReadProjectConfig :: Rebuild ProjectConfig
      phaseReadProjectConfig = do
        liftIO $ do
          info verbosity "Project settings changed, reconfiguring..."
  
        readProjectConfig verbosity projectConfigConfigFile
          projectConfigSendMetrics distDirLayout
  
      -- Look for all the cabal packages in the project
      -- some of which may be local src dirs, tarballs etc
      --
      phaseReadLocalPackages :: ProjectConfig
                             -> Rebuild [PackageSpecifier UnresolvedSourcePackage]
      phaseReadLocalPackages projectConfig = do
        localCabalFiles <- findProjectPackages distDirLayout projectConfig
  
        -- Create folder only if findProjectPackages did not throw a
        -- BadPackageLocations exception.
        liftIO $ do
          createDirectoryIfMissingVerbose verbosity True distDirectory
          createDirectoryIfMissingVerbose verbosity True distProjectCacheDirectory
  
        mapM (readSourcePackage verbosity distDirLayout) localCabalFiles
  
  
  -- | Return an up-to-date elaborated install plan.
  --
  -- Two variants of the install plan are returned: with and without packages
  -- from the store. That is, the \"improved\" plan where source packages are
  -- replaced by pre-existing installed packages from the store (when their ids
  -- match), and also the original elaborated plan which uses primarily source
  -- packages.
  
  -- The improved plan is what we use for building, but the original elaborated
  -- plan is useful for reporting and configuration. For example the @freeze@
  -- command needs the source package info to know about flag choices and
  -- dependencies of executables and setup scripts.
  --
  rebuildInstallPlan :: Verbosity
                     -> DistDirLayout -> CabalDirLayout
                     -> ProjectConfig
                     -> [PackageSpecifier UnresolvedSourcePackage]
                     -> IO ( ElaboratedInstallPlan  -- with store packages
                           , ElaboratedInstallPlan  -- with source packages
                           , ElaboratedSharedConfig )
                        -- ^ @(improvedPlan, elaboratedPlan, _, _)@
  rebuildInstallPlan verbosity
                     distDirLayout@DistDirLayout {
                       distProjectRootDirectory,
                       distProjectCacheFile
                     }
                     CabalDirLayout {
                       cabalStoreDirLayout
                     } = \projectConfig localPackages ->
      runRebuild distProjectRootDirectory $ do
      progsearchpath <- liftIO $ getSystemSearchPath
      let projectConfigMonitored = projectConfig { projectConfigBuildOnly = mempty }
  
      -- The overall improved plan is cached
      rerunIfChanged verbosity fileMonitorImprovedPlan
                     -- react to changes in the project config,
                     -- the package .cabal files and the path
                     (projectConfigMonitored, localPackages, progsearchpath) $ do
  
        -- And so is the elaborated plan that the improved plan based on
        (elaboratedPlan, elaboratedShared) <-
          rerunIfChanged verbosity fileMonitorElaboratedPlan
                         (projectConfigMonitored, localPackages,
                          progsearchpath) $ do
  
            compilerEtc   <- phaseConfigureCompiler projectConfig
            _             <- phaseConfigurePrograms projectConfig compilerEtc
            (solverPlan, pkgConfigDB)
                          <- phaseRunSolver         projectConfig
                                                    compilerEtc
                                                    localPackages
            (elaboratedPlan,
             elaboratedShared) <- phaseElaboratePlan projectConfig
                                                     compilerEtc pkgConfigDB
                                                     solverPlan
                                                     localPackages
  
            phaseMaintainPlanOutputs elaboratedPlan elaboratedShared
            return (elaboratedPlan, elaboratedShared)
  
        -- The improved plan changes each time we install something, whereas
        -- the underlying elaborated plan only changes when input config
        -- changes, so it's worth caching them separately.
        improvedPlan <- phaseImprovePlan elaboratedPlan elaboratedShared
  
        return (improvedPlan, elaboratedPlan, elaboratedShared)
  
    where
      fileMonitorCompiler       = newFileMonitorInCacheDir "compiler"
      fileMonitorSolverPlan     = newFileMonitorInCacheDir "solver-plan"
      fileMonitorSourceHashes   = newFileMonitorInCacheDir "source-hashes"
      fileMonitorElaboratedPlan = newFileMonitorInCacheDir "elaborated-plan"
      fileMonitorImprovedPlan   = newFileMonitorInCacheDir "improved-plan"
  
      newFileMonitorInCacheDir :: Eq a => FilePath -> FileMonitor a b
      newFileMonitorInCacheDir  = newFileMonitor . distProjectCacheFile
  
  
      -- Configure the compiler we're using.
      --
      -- This is moderately expensive and doesn't change that often so we cache
      -- it independently.
      --
      phaseConfigureCompiler :: ProjectConfig
                             -> Rebuild (Compiler, Platform, ProgramDb)
      phaseConfigureCompiler ProjectConfig {
                               projectConfigShared = ProjectConfigShared {
                                 projectConfigHcFlavor,
                                 projectConfigHcPath,
                                 projectConfigHcPkg,
                                 projectConfigEtaVersion
                               },
                               projectConfigLocalPackages = PackageConfig {
                                 packageConfigProgramPaths,
                                 packageConfigProgramArgs,
                                 packageConfigProgramPathExtra
                               },
                               projectConfigBuildOnly
                             } = do
          progsearchpath <- liftIO $ getSystemSearchPath
          rerunIfChanged verbosity fileMonitorCompiler
                         (hcFlavor, hcPath, hcPkg, etaVersion, progsearchpath,
                          packageConfigProgramPaths,
                          packageConfigProgramArgs,
                          packageConfigProgramPathExtra) $ do
  
            liftIO $ info verbosity "Compiler settings changed, reconfiguring..."
            result@(_, _, progdb') <- liftIO $
              Cabal.configCompilerEx
                hcFlavor hcPath hcPkg
                progdb verbosity
  
          -- Note that we added the user-supplied program locations and args
          -- for /all/ programs, not just those for the compiler prog and
          -- compiler-related utils. In principle we don't know which programs
          -- the compiler will configure (and it does vary between compilers).
          -- We do know however that the compiler will only configure the
          -- programs it cares about, and those are the ones we monitor here.
  
          -- We need to monitor the Eta pointer file for changes in between builds,
          -- otherwise we get an incorrect "Up to date" after switching.
            monitorFiles (monitorFile (etaPointerFile binariesPath) :
                          programsMonitorFiles progdb')
  
            return result
        where
          hcFlavor   = flagToMaybe projectConfigHcFlavor
          hcPath     = flagToMaybe projectConfigHcPath
          hcPkg      = flagToMaybe projectConfigHcPkg
          etaVersion = flagToMaybe projectConfigEtaVersion
          binariesPath = Cabal.fromFlag $ projectConfigBinariesDir projectConfigBuildOnly
          progdb     =
              userSpecifyPaths (Map.toList (getMapLast packageConfigProgramPaths))
            . userSpecifyArgss (Map.toList (getMapMappend packageConfigProgramArgs))
            . modifyProgramSearchPath
                (++ [ ProgramSearchPathDir dir
                    | dir <- fromNubList packageConfigProgramPathExtra ])
            $ defaultProgramDb
  
  
      -- Configuring other programs.
      --
      -- Having configred the compiler, now we configure all the remaining
      -- programs. This is to check we can find them, and to monitor them for
      -- changes.
      --
      -- TODO: [required eventually] we don't actually do this yet.
      --
      -- We rely on the fact that the previous phase added the program config for
      -- all local packages, but that all the programs configured so far are the
      -- compiler program or related util programs.
      --
      phaseConfigurePrograms :: ProjectConfig
                             -> (Compiler, Platform, ProgramDb)
                             -> Rebuild ()
      phaseConfigurePrograms projectConfig (_, _, compilerprogdb) = do
          -- Users are allowed to specify program locations independently for
          -- each package (e.g. to use a particular version of a pre-processor
          -- for some packages). However they cannot do this for the compiler
          -- itself as that's just not going to work. So we check for this.
          liftIO $ checkBadPerPackageCompilerPaths
            (configuredPrograms compilerprogdb)
            (getMapMappend (projectConfigSpecificPackage projectConfig))
  
          --TODO: [required eventually] find/configure other programs that the
          -- user specifies.
  
          --TODO: [required eventually] find/configure all build-tools
          -- but note that some of them may be built as part of the plan.
  
  
      -- Run the solver to get the initial install plan.
      -- This is expensive so we cache it independently.
      --
      phaseRunSolver :: ProjectConfig
                     -> (Compiler, Platform, ProgramDb)
                     -> [PackageSpecifier UnresolvedSourcePackage]
                     -> Rebuild (SolverInstallPlan, PkgConfigDb)
      phaseRunSolver projectConfig@ProjectConfig {
                       projectConfigShared,
                       projectConfigBuildOnly
                     }
                     (compiler, platform, progdb)
                     localPackages =
          rerunIfChanged verbosity fileMonitorSolverPlan
                         (solverSettings,
                          localPackages, localPackagesEnabledStanzas,
                          compiler, platform, programDbSignature progdb) $ do
  
            installedPkgIndex <- getInstalledPackages verbosity
                                                      compiler progdb platform
                                                      corePackageDbs
            sourcePkgDb       <- getSourcePackages verbosity withRepoCtx binariesPath
                                   (solverSettingIndexState solverSettings)
            pkgConfigDB       <- getPkgConfigDb verbosity progdb
  
            --TODO: [code cleanup] it'd be better if the Compiler contained the
            -- ConfiguredPrograms that it needs, rather than relying on the progdb
            -- since we don't need to depend on all the programs here, just the
            -- ones relevant for the compiler.
  
            liftIO $ do
              solver <- chooseSolver verbosity
                                     (solverSettingSolver solverSettings)
                                     (compilerInfo compiler)
  
              notice verbosity "Resolving dependencies..."
              plan <- withFile (distProjectCacheFile "solver-trace") WriteMode $ \h ->
                foldProgress (logMsg h) (die' verbosity) return $
                  planPackages verbosity compiler platform solver solverSettings
                              installedPkgIndex sourcePkgDb pkgConfigDB
                              localPackages localPackagesEnabledStanzas
              return (plan, pkgConfigDB)
        where
          -- Note: In the presence of extra package dbs, we add in the storePackageDbs
          --       because it is likely that the packages in the extra package dbs
          --       depend on them. We may want to add this behind an additional flag
          --       if this causes problems.
          corePackageDbs
            | null extraPackageDbs = [GlobalPackageDB]
            | otherwise = [GlobalPackageDB]
                       ++ filter (/= GlobalPackageDB) (extraPackageDbs ++ storePackageDbs)
          -- TODO: catMaybes seems like the wrong behavior here. I think we need something
          --       that strips off the list until the last Nothing.
          extraPackageDbs = catMaybes (projectConfigPackageDBs projectConfigShared)
          storePackageDbs = storePackageDBStack cabalStoreDirLayout (compilerId compiler)
          withRepoCtx    = projectConfigWithSolverRepoContext verbosity
                             projectConfigShared
                             projectConfigBuildOnly
          binariesPath = Cabal.fromFlag $ projectConfigBinariesDir projectConfigBuildOnly
          solverSettings = resolveSolverSettings projectConfig
          logMsg h message rest = do
            debugNoWrap verbosity message
            hPutStrLn h message
            rest
  
          localPackagesEnabledStanzas =
            Map.fromList
              [ (pkgname, stanzas)
              | pkg <- localPackages
              , let pkgname            = pkgSpecifierTarget pkg
                    testsEnabled       = lookupLocalPackageConfig
                                           packageConfigTests
                                           projectConfig pkgname
                    benchmarksEnabled  = lookupLocalPackageConfig
                                           packageConfigBenchmarks
                                           projectConfig pkgname
                    stanzas =
                      Map.fromList $
                        [ (TestStanzas, enabled)
                        | enabled <- flagToList testsEnabled ]
                     ++ [ (BenchStanzas , enabled)
                        | enabled <- flagToList benchmarksEnabled ]
              ]
  
      -- Elaborate the solver's install plan to get a fully detailed plan. This
      -- version of the plan has the final nix-style hashed ids.
      --
      phaseElaboratePlan :: ProjectConfig
                         -> (Compiler, Platform, ProgramDb)
                         -> PkgConfigDb
                         -> SolverInstallPlan
                         -> [PackageSpecifier UnresolvedSourcePackage]
                         -> Rebuild ( ElaboratedInstallPlan
                                    , ElaboratedSharedConfig )
      phaseElaboratePlan ProjectConfig {
                           projectConfigShared,
                           projectConfigAllPackages,
                           projectConfigLocalPackages,
                           projectConfigSpecificPackage,
                           projectConfigBuildOnly
                         }
                         (compiler, platform, progdb) pkgConfigDB
                         solverPlan localPackages = do
  
          liftIO $ debug verbosity "Elaborating the install plan..."
  
          sourcePackageHashes <-
            rerunIfChanged verbosity fileMonitorSourceHashes
                           (packageLocationsSignature solverPlan) $
              getPackageSourceHashes verbosity withRepoCtx solverPlan
  
          defaultInstallDirs <- liftIO $ userInstallDirTemplates compiler
          (elaboratedPlan, elaboratedShared)
            <- liftIO . runLogProgress verbosity $
                elaborateInstallPlan
                  verbosity
                  platform compiler progdb pkgConfigDB
                  distDirLayout
                  cabalStoreDirLayout
                  solverPlan
                  localPackages
                  sourcePackageHashes
                  defaultInstallDirs
                  projectConfigShared
                  projectConfigAllPackages
                  projectConfigLocalPackages
                  (getMapMappend projectConfigSpecificPackage)
          let instantiatedPlan = instantiateInstallPlan elaboratedPlan
          liftIO $ debugNoWrap verbosity (InstallPlan.showInstallPlan instantiatedPlan)
          return (instantiatedPlan, elaboratedShared)
        where
          withRepoCtx = projectConfigWithSolverRepoContext verbosity
                          projectConfigShared
                          projectConfigBuildOnly
  
      -- Update the files we maintain that reflect our current build environment.
      -- In particular we maintain a JSON representation of the elaborated
      -- install plan (but not the improved plan since that reflects the state
      -- of the build rather than just the input environment).
      --
      phaseMaintainPlanOutputs :: ElaboratedInstallPlan
                               -> ElaboratedSharedConfig
                               -> Rebuild ()
      phaseMaintainPlanOutputs elaboratedPlan elaboratedShared = liftIO $ do
          debug verbosity "Updating plan.json"
          writePlanExternalRepresentation
            distDirLayout
            elaboratedPlan
            elaboratedShared
  
  
      -- Improve the elaborated install plan. The elaborated plan consists
      -- mostly of source packages (with full nix-style hashed ids). Where
      -- corresponding installed packages already exist in the store, replace
      -- them in the plan.
      --
      -- Note that we do monitor the store's package db here, so we will redo
      -- this improvement phase when the db changes -- including as a result of
      -- executing a plan and installing things.
      --
      phaseImprovePlan :: ElaboratedInstallPlan
                       -> ElaboratedSharedConfig
                       -> Rebuild ElaboratedInstallPlan
      phaseImprovePlan elaboratedPlan elaboratedShared = do
  
          liftIO $ debug verbosity "Improving the install plan..."
          storePkgIdSet <- getStoreEntries cabalStoreDirLayout compid
          let improvedPlan = improveInstallPlanWithInstalledPackages
                               storePkgIdSet
                               elaboratedPlan
          liftIO $ debugNoWrap verbosity (InstallPlan.showInstallPlan improvedPlan)
          -- TODO: [nice to have] having checked which packages from the store
          -- we're using, it may be sensible to sanity check those packages
          -- by loading up the compiler package db and checking everything
          -- matches up as expected, e.g. no dangling deps, files deleted.
          return improvedPlan
        where
          compid = compilerId (pkgConfigCompiler elaboratedShared)
  
  
  programsMonitorFiles :: ProgramDb -> [MonitorFilePath]
  programsMonitorFiles progdb =
      [ monitor
      | prog    <- configuredPrograms progdb
      , monitor <- monitorFileSearchPath (programMonitorFiles prog)
                                         (programPath prog)
      ]
  
  -- | Select the bits of a 'ProgramDb' to monitor for value changes.
  -- Use 'programsMonitorFiles' for the files to monitor.
  --
  programDbSignature :: ProgramDb -> [ConfiguredProgram]
  programDbSignature progdb =
      [ prog { programMonitorFiles = []
             , programOverrideEnv  = filter ((/="PATH") . fst)
                                            (programOverrideEnv prog) }
      | prog <- configuredPrograms progdb ]
  
  getInstalledPackages :: Verbosity
                       -> Compiler -> ProgramDb -> Platform
                       -> PackageDBStack
                       -> Rebuild InstalledPackageIndex
  getInstalledPackages verbosity compiler progdb platform packagedbs = do
      monitorFiles . map monitorFileOrDirectory
        =<< liftIO (IndexUtils.getInstalledPackagesMonitorFiles
                      verbosity compiler
                      packagedbs progdb platform)
      liftIO $ IndexUtils.getInstalledPackages
                 verbosity compiler
                 packagedbs progdb
  
  {-
  --TODO: [nice to have] use this but for sanity / consistency checking
  getPackageDBContents :: Verbosity
                       -> Compiler -> ProgramDb -> Platform
                       -> PackageDB
                       -> Rebuild InstalledPackageIndex
  getPackageDBContents verbosity compiler progdb platform packagedb = do
      monitorFiles . map monitorFileOrDirectory
        =<< liftIO (IndexUtils.getInstalledPackagesMonitorFiles
                      verbosity compiler
                      [packagedb] progdb platform)
      liftIO $ do
        createPackageDBIfMissing verbosity compiler progdb packagedb
        Cabal.getPackageDBContents verbosity compiler
                                   packagedb progdb
  -}
  
  getSourcePackages :: Verbosity -> (forall a. (RepoContext -> IO a) -> IO a)
                    -> FilePath -> Maybe IndexUtils.IndexState
                    -> Rebuild SourcePackageDb
  getSourcePackages verbosity withRepoCtx binariesPath idxState = do
      (sourcePkgDb, repos) <-
        liftIO $
          withRepoCtx $ \repoctx -> do
            sourcePkgDb <- IndexUtils.getSourcePackagesAtIndexState verbosity
                             repoctx binariesPath idxState
            return (sourcePkgDb, repoContextRepos repoctx)
  
      mapM_ needIfExists
          . IndexUtils.getSourcePackagesMonitorFiles
          $ repos
      return sourcePkgDb
  
  
  getPkgConfigDb :: Verbosity -> ProgramDb -> Rebuild PkgConfigDb
  getPkgConfigDb verbosity progdb = do
      dirs <- liftIO $ getPkgConfigDbDirs verbosity progdb
      -- Just monitor the dirs so we'll notice new .pc files.
      -- Alternatively we could monitor all the .pc files too.
      mapM_ monitorDirectoryStatus dirs
      liftIO $ readPkgConfigDb verbosity progdb
  
  
  -- | Select the config values to monitor for changes package source hashes.
  packageLocationsSignature :: SolverInstallPlan
                            -> [(PackageId, PackageLocation (Maybe FilePath))]
  packageLocationsSignature solverPlan =
      [ (packageId pkg, packageSource pkg)
      | SolverInstallPlan.Configured (SolverPackage { solverPkgSource = pkg})
          <- SolverInstallPlan.toList solverPlan
      ]
  
  
  -- | Get the 'HashValue' for all the source packages where we use hashes,
  -- and download any packages required to do so.
  --
  -- Note that we don't get hashes for local unpacked packages.
  --
  getPackageSourceHashes :: Verbosity
                         -> (forall a. (RepoContext -> IO a) -> IO a)
                         -> SolverInstallPlan
                         -> Rebuild (Map PackageId PackageSourceHash)
  getPackageSourceHashes verbosity withRepoCtx solverPlan = do
  
      -- Determine if and where to get the package's source hash from.
      --
      let allPkgLocations :: [(PackageId, PackageLocation (Maybe FilePath), [FilePath])]
          allPkgLocations =
            [ (packageId pkg, packageSource pkg, sourcePackagePatches pkg)
            | SolverInstallPlan.Configured (SolverPackage { solverPkgSource = pkg})
                <- SolverInstallPlan.toList solverPlan ]
  
          -- Tarballs that were local in the first place.
          -- We'll hash these tarball files directly.
          localTarballPkgs :: [(PackageId, FilePath, [FilePath])]
          localTarballPkgs =
            [ (pkgid, tarball, patches)
            | (pkgid, LocalTarballPackage tarball isBinary, patches) <- allPkgLocations
            , not isBinary ]
            -- Ignore binary tarballs since there's no need to calculate
            -- source hashes (for now).
  
          -- Tarballs from remote URLs. We must have downloaded these already
          -- (since we extracted the .cabal file earlier)
          --TODO: [required eventually] finish remote tarball functionality
  --        allRemoteTarballPkgs =
  --          [ (pkgid, )
  --          | (pkgid, RemoteTarballPackage ) <- allPkgLocations ]
  
          hashesFromScmPkgs :: Map PackageId HashValue
          hashesFromScmPkgs = Map.fromList
            [ (pkgid, hashString (show sourceRepos))
            | (pkgid, ScmPackage _ sourceRepos _ _ , _patches) <- allPkgLocations ]
  
          -- Tarballs from repositories, either where the repository provides
          -- hashes as part of the repo metadata, or where we will have to
          -- download and hash the tarball.
          repoTarballPkgsWithMetadata    :: [(PackageId, Repo, [FilePath])]
          repoTarballPkgsWithoutMetadata :: [(PackageId, Repo, [FilePath])]
          (repoTarballPkgsWithMetadata,
           repoTarballPkgsWithoutMetadata) =
            partitionEithers
            [ case repo of
                RepoSecure{} -> Left  (pkgid, repo, patches)
                _            -> Right (pkgid, repo, patches)
            | (pkgid, RepoTarballPackage repo _ _, patches) <- allPkgLocations ]
  
          includePatchHashes pkgid hash patches
            | null patches = return (pkgid, hash)
            | otherwise    = do
                patchHashes <- mapM readFileHashValue patches
                return (pkgid, mconcat (hash : patchHashes))
  
          first  (a,_,_) = a
          second (_,b,_) = b
          third  (_,_,c) = c
  
      -- For tarballs from repos that do not have hashes available we now have
      -- to check if the packages were downloaded already.
      --
      (repoTarballPkgsToDownload,
       repoTarballPkgsDownloaded)
        <- fmap partitionEithers $
           liftIO $ sequence
             [ do mtarball <- checkRepoTarballFetched repo pkgid
                  case mtarball of
                    Nothing      -> return (Left  (pkgid, repo, patches))
                    Just tarball -> return (Right (pkgid, tarball, patches))
             | (pkgid, repo, patches) <- repoTarballPkgsWithoutMetadata ]
  
      (hashesFromRepoMetadata,
       repoTarballPkgsNewlyDownloaded) <-
        -- Avoid having to initialise the repository (ie 'withRepoCtx') if we
        -- don't have to. (The main cost is configuring the http client.)
        if null repoTarballPkgsToDownload && null repoTarballPkgsWithMetadata
        then return (Map.empty, [])
        else liftIO $ withRepoCtx $ \repoctx -> do
  
        -- For tarballs from repos that do have hashes available as part of the
        -- repo metadata we now load up the index for each repo and retrieve
        -- the hashes for the packages
        --
        hashesFromRepoMetadata <-
          Sec.uncheckClientErrors $ --TODO: [code cleanup] wrap in our own exceptions
          fmap (Map.fromList . concat) $
          sequence
            -- Reading the repo index is expensive so we group the packages by repo
            [ repoContextWithSecureRepo repoctx repo $ \secureRepo ->
                Sec.withIndex secureRepo $ \repoIndex ->
                  sequence
                    [ do hash <- Sec.trusted <$> -- strip off Trusted tag
                                 Sec.indexLookupHash repoIndex pkgid
                         -- Note that hackage-security currently uses SHA256
                         -- but this API could in principle give us some other
                         -- choice in future.
                         includePatchHashes pkgid (hashFromTUF hash) patch
                    | (pkgid,patch) <- zip pkgids patches ]
            | (repo, pkgids, patches) <-
                  map (\grp@((_,repo,_):_) -> (repo, map first grp, map third grp))
                . groupBy ((==)    `on` (remoteRepoName . repoRemote . second))
                . sortBy  (compare `on` (remoteRepoName . repoRemote . second))
                $ repoTarballPkgsWithMetadata
            ]
  
        -- For tarballs from repos that do not have hashes available, download
        -- the ones we previously determined we need.
        --
        repoTarballPkgsNewlyDownloaded <-
          sequence
            [ do tarball <- fetchRepoTarball verbosity repoctx repo pkgid
                 return (pkgid, tarball, patches)
            | (pkgid, repo, patches) <- repoTarballPkgsToDownload ]
  
        return (hashesFromRepoMetadata,
                repoTarballPkgsNewlyDownloaded)
  
      -- Hash tarball files for packages where we have to do that. This includes
      -- tarballs that were local in the first place, plus tarballs from repos,
      -- either previously cached or freshly downloaded.
      --
      let allTarballFilePkgs :: [(PackageId, FilePath, [FilePath])]
          allTarballFilePkgs = localTarballPkgs
                            ++ repoTarballPkgsDownloaded
                            ++ repoTarballPkgsNewlyDownloaded
      hashesFromTarballFiles <- liftIO $
        fmap Map.fromList $
        sequence
          [ do srchash <- readFileHashValue tarball
               includePatchHashes pkgid srchash patches
          | (pkgid, tarball, patches) <- allTarballFilePkgs
          ]
  
      -- Monitor the tarballs for any changes
      monitorFiles
        $ concat [ monitorFile tarball : map monitorFileHashed patches
                 | (_pkgid, tarball, patches) <- allTarballFilePkgs ]
  
      -- Monitor the patches for secure repos (not included above)
      monitorFiles
        $ concat [ map monitorFileHashed patches
                 | (_pkgid, _repo, patches) <- repoTarballPkgsWithMetadata ]
  
      -- Return the combination
      return $! hashesFromRepoMetadata
             <> hashesFromTarballFiles
             <> hashesFromScmPkgs
  
  
  -- ------------------------------------------------------------
  -- * Installation planning
  -- ------------------------------------------------------------
  
  planPackages :: Verbosity
               -> Compiler
               -> Platform
               -> Solver -> SolverSettings
               -> InstalledPackageIndex
               -> SourcePackageDb
               -> PkgConfigDb
               -> [PackageSpecifier UnresolvedSourcePackage]
               -> Map PackageName (Map OptionalStanza Bool)
               -> Progress String String SolverInstallPlan
  planPackages verbosity comp platform solver SolverSettings{..}
               installedPkgIndex sourcePkgDb pkgConfigDB
               localPackages pkgStanzasEnable =
  
      resolveDependencies
        platform (compilerInfo comp)
        pkgConfigDB solver
        resolverParams
  
    where
  
      --TODO: [nice to have] disable multiple instances restriction in the solver, but then
      -- make sure we can cope with that in the output.
      resolverParams =
  
          setMaxBackjumps solverSettingMaxBackjumps
  
        . setIndependentGoals solverSettingIndependentGoals
  
        . setReorderGoals solverSettingReorderGoals
  
        . setCountConflicts solverSettingCountConflicts
  
          --TODO: [required eventually] should only be configurable for custom installs
     -- . setAvoidReinstalls solverSettingAvoidReinstalls
  
          --TODO: [required eventually] should only be configurable for custom installs
     -- . setShadowPkgs solverSettingShadowPkgs
  
        . setStrongFlags solverSettingStrongFlags
  
        . setAllowBootLibInstalls solverSettingAllowBootLibInstalls
  
        . setSolverVerbosity verbosity
  
          --TODO: [required eventually] decide if we need to prefer installed for
          -- global packages, or prefer latest even for global packages. Perhaps
          -- should be configurable but with a different name than "upgrade-dependencies".
        . setPreferenceDefault PreferLatestForSelected
                             {-(if solverSettingUpgradeDeps
                                  then PreferAllLatest
                                  else PreferLatestForSelected)-}
  
        . removeLowerBounds solverSettingAllowOlder
        . removeUpperBounds solverSettingAllowNewer
  
        . addDefaultSetupDependencies (defaultSetupDeps comp platform
                                     . PD.packageDescription
                                     . packageDescription)
  
        . addSetupCabalMinVersionConstraint (mkVersion [1,20])
            -- While we can talk to older Cabal versions (we need to be able to
            -- do so for custom Setup scripts that require older Cabal lib
            -- versions), we have problems talking to some older versions that
            -- don't support certain features.
            --
            -- For example, Cabal-1.16 and older do not know about build targets.
            -- Even worse, 1.18 and older only supported the --constraint flag
            -- with source package ids, not --dependency with installed package
            -- ids. That is bad because we cannot reliably select the right
            -- dependencies in the presence of multiple instances (i.e. the
            -- store). See issue #3932. So we require Cabal 1.20 as a minimum.
  
        . addPreferences
            -- preferences from the config file or command line
            [ PackageVersionPreference name ver
            | Dependency name ver <- solverSettingPreferences ]
  
        . addConstraints
            -- version constraints from the config file or command line
              [ LabeledPackageConstraint (userToPackageConstraint pc) src
              | (pc, src) <- solverSettingConstraints ]
  
        . addPreferences
            -- enable stanza preference where the user did not specify
            [ PackageStanzasPreference pkgname stanzas
            | pkg <- localPackages
            , let pkgname = pkgSpecifierTarget pkg
                  stanzaM = Map.findWithDefault Map.empty pkgname pkgStanzasEnable
                  stanzas = [ stanza | stanza <- [minBound..maxBound]
                            , Map.lookup stanza stanzaM == Nothing ]
            , not (null stanzas)
            ]
  
        . addConstraints
            -- enable stanza constraints where the user asked to enable
            [ LabeledPackageConstraint
                (PackageConstraint (scopeToplevel pkgname)
                                   (PackagePropertyStanzas stanzas))
                ConstraintSourceConfigFlagOrTarget
            | pkg <- localPackages
            , let pkgname = pkgSpecifierTarget pkg
                  stanzaM = Map.findWithDefault Map.empty pkgname pkgStanzasEnable
                  stanzas = [ stanza | stanza <- [minBound..maxBound]
                            , Map.lookup stanza stanzaM == Just True ]
            , not (null stanzas)
            ]
  
        . addConstraints
            --TODO: [nice to have] should have checked at some point that the
            -- package in question actually has these flags.
            [ LabeledPackageConstraint
                (PackageConstraint (scopeToplevel pkgname)
                                   (PackagePropertyFlags flags))
                ConstraintSourceConfigFlagOrTarget
            | (pkgname, flags) <- Map.toList solverSettingFlagAssignments ]
  
        . addConstraints
            --TODO: [nice to have] we have user-supplied flags for unspecified
            -- local packages (as well as specific per-package flags). For the
            -- former we just apply all these flags to all local targets which
            -- is silly. We should check if the flags are appropriate.
            [ LabeledPackageConstraint
                (PackageConstraint (scopeToplevel pkgname)
                                   (PackagePropertyFlags flags))
                ConstraintSourceConfigFlagOrTarget
            | let flags = solverSettingFlagAssignment
            , not (null flags)
            , pkg <- localPackages
            , let pkgname = pkgSpecifierTarget pkg ]
  
        $ stdResolverParams
  
      stdResolverParams =
        -- Note: we don't use the standardInstallPolicy here, since that uses
        -- its own addDefaultSetupDependencies that is not appropriate for us.
        basicInstallPolicy
          installedPkgIndex sourcePkgDb
          localPackages
  
  
  ------------------------------------------------------------------------------
  -- * Install plan post-processing
  ------------------------------------------------------------------------------
  
  -- This phase goes from the InstallPlan we get from the solver and has to
  -- make an elaborated install plan.
  --
  -- We go in two steps:
  --
  --  1. elaborate all the source packages that the solver has chosen.
  --  2. swap source packages for pre-existing installed packages wherever
  --     possible.
  --
  -- We do it in this order, elaborating and then replacing, because the easiest
  -- way to calculate the installed package ids used for the replacement step is
  -- from the elaborated configuration for each package.
  
  
  
  
  ------------------------------------------------------------------------------
  -- * Install plan elaboration
  ------------------------------------------------------------------------------
  
  -- Note [SolverId to ConfiguredId]
  -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  -- Dependency solving is a per package affair, so after we're done, we
  -- end up with 'SolverInstallPlan' that records in 'solverPkgLibDeps'
  -- and 'solverPkgExeDeps' what packages provide the libraries and executables
  -- needed by each component of the package (phew!)  For example, if I have
  --
  --      library
  --          build-depends: lib
  --          build-tool-depends: pkg:exe1
  --          build-tools: alex
  --
  -- After dependency solving, I find out that this library component has
  -- library dependencies on lib-0.2, and executable dependencies on pkg-0.1
  -- and alex-0.3 (other components of the package may have different
  -- dependencies).  Note that I've "lost" the knowledge that I depend
  -- *specifically* on the exe1 executable from pkg.
  --
  -- So, we have a this graph of packages, and we need to transform it into
  -- a graph of components which we are actually going to build.  In particular:
  --
  -- NODE changes from PACKAGE (SolverPackage) to COMPONENTS (ElaboratedConfiguredPackage)
  -- EDGE changes from PACKAGE DEP (SolverId) to COMPONENT DEPS (ConfiguredId)
  --
  -- In both cases, what was previously a single node/edge may turn into multiple
  -- nodes/edges.  Multiple components, because there may be multiple components
  -- in a package; multiple component deps, because we may depend upon multiple
  -- executables from the same package (and maybe, some day, multiple libraries
  -- from the same package.)
  --
  -- Let's talk about how to do this transformation. Naively, we might consider
  -- just processing each package, converting it into (zero or) one or more
  -- components.  But we also have to update the edges; this leads to
  -- two complications:
  --
  --      1. We don't know what the ConfiguredId of a component is until
  --      we've configured it, but we cannot configure a component unless
  --      we know the ConfiguredId of all its dependencies.  Thus, we must
  --      process the 'SolverInstallPlan' in topological order.
  --
  --      2. When we process a package, we know the SolverIds of its
  --      dependencies, but we have to do some work to turn these into
  --      ConfiguredIds.  For example, in the case of build-tool-depends, the
  --      SolverId isn't enough to uniquely determine the ConfiguredId we should
  --      elaborate to: we have to look at the executable name attached to
  --      the package name in the package description to figure it out.
  --      At the same time, we NEED to use the SolverId, because there might
  --      be multiple versions of the same package in the build plan
  --      (due to setup dependencies); we can't just look up the package name
  --      from the package description.
  --
  -- However, we do have the following INVARIANT: a component never directly
  -- depends on multiple versions of the same package.  Thus, we can
  -- adopt the following strategy:
  --
  --      * When a package is transformed into components, record
  --        a mapping from SolverId to ALL of the components
  --        which were elaborated.
  --
  --      * When we look up an edge, we use our knowledge of the
  --        component name to *filter* the list of components into
  --        the ones we actually wanted to refer to.
  --
  -- By the way, we can tell that SolverInstallPlan is not the "right" type
  -- because a SolverId cannot adequately represent all possible dependency
  -- solver states: we may need to record foo-0.1 multiple times in
  -- the solver install plan with different dependencies.  The solver probably
  -- doesn't handle this correctly... but it should.  The right way to solve
  -- this is to come up with something very much like a 'ConfiguredId', in that
  -- it incorporates the version choices of its dependencies, but less
  -- fine grained.  Fortunately, this doesn't seem to have affected anyone,
  -- but it is good to watch out about.
  
  
  -- | Produce an elaborated install plan using the policy for local builds with
  -- a nix-style shared store.
  --
  -- In theory should be able to make an elaborated install plan with a policy
  -- matching that of the classic @etlas install --user@ or @--global@
  --
  elaborateInstallPlan
    :: Verbosity -> Platform -> Compiler -> ProgramDb -> PkgConfigDb
    -> DistDirLayout
    -> StoreDirLayout
    -> SolverInstallPlan
    -> [PackageSpecifier UnresolvedSourcePackage]
    -> Map PackageId PackageSourceHash
    -> InstallDirs.InstallDirTemplates
    -> ProjectConfigShared
    -> PackageConfig
    -> PackageConfig
    -> Map PackageName PackageConfig
    -> LogProgress (ElaboratedInstallPlan, ElaboratedSharedConfig)
  elaborateInstallPlan verbosity platform compiler compilerprogdb pkgConfigDB
                       distDirLayout@DistDirLayout{..}
                       storeDirLayout@StoreDirLayout{storePackageDBStack}
                       solverPlan localPackages
                       sourcePackageHashes
                       defaultInstallDirs
                       sharedPackageConfig
                       allPackagesConfig
                       localPackagesConfig
                       perPackageConfig = do
      x <- elaboratedInstallPlan
      return (x, elaboratedSharedConfig)
    where
      elaboratedSharedConfig =
        ElaboratedSharedConfig {
          pkgConfigPlatform      = platform,
          pkgConfigCompiler      = compiler,
          pkgConfigCompilerProgs = compilerprogdb
        }
  
      preexistingInstantiatedPkgs =
          Map.fromList (mapMaybe f (SolverInstallPlan.toList solverPlan))
        where
          f (SolverInstallPlan.PreExisting inst)
              | let ipkg = instSolverPkgIPI inst
              , not (IPI.indefinite ipkg)
              = Just (IPI.installedUnitId ipkg,
                       (FullUnitId (IPI.installedComponentId ipkg)
                                   (Map.fromList (IPI.instantiatedWith ipkg))))
          f _ = Nothing
  
      elaboratedInstallPlan =
        flip InstallPlan.fromSolverInstallPlanWithProgress solverPlan $ \mapDep planpkg ->
          case planpkg of
            SolverInstallPlan.PreExisting pkg ->
              return [InstallPlan.PreExisting (instSolverPkgIPI pkg)]
  
            SolverInstallPlan.Configured  pkg ->
              let inplace_doc | shouldBuildInplaceOnly pkg = text "inplace"
                              | otherwise                  = Disp.empty
              in addProgressCtx (text "In the" <+> inplace_doc <+> text "package" <+>
                               quotes (disp (packageId pkg))) $
                 map InstallPlan.Configured <$> elaborateSolverToComponents mapDep pkg
  
      -- NB: We don't INSTANTIATE packages at this point.  That's
      -- a post-pass.  This makes it simpler to compute dependencies.
      elaborateSolverToComponents
          :: (SolverId -> [ElaboratedPlanPackage])
          -> SolverPackage UnresolvedPkgLoc
          -> LogProgress [ElaboratedConfiguredPackage]
      elaborateSolverToComponents mapDep spkg@(SolverPackage _ _ _ deps0 exe_deps0)
          = case mkComponentsGraph (elabEnabledSpec elab0) pd of
             Right g -> do
              let src_comps = componentsGraphToList g
              infoProgress $ hang (text "Component graph for" <+> disp pkgid <<>> colon)
                              4 (dispComponentsWithDeps src_comps)
              (_, comps) <- mapAccumM buildComponent
                              (Map.empty, Map.empty, Map.empty)
                              (map fst src_comps)
              let not_per_component_reasons = why_not_per_component src_comps
              if null not_per_component_reasons
                  then return comps
                  else do checkPerPackageOk comps not_per_component_reasons
                          return [elaborateSolverToPackage mapDep spkg g $
                                  comps ++ maybeToList setupComponent]
             Left cns ->
              dieProgress $
                  hang (text "Dependency cycle between the following components:") 4
                       (vcat (map (text . componentNameStanza) cns))
        where
          -- You are eligible to per-component build if this list is empty
          why_not_per_component g
              = cuz_custom ++ cuz_spec ++ cuz_length ++ cuz_flag
            where
              cuz reason = [text reason]
              -- At this point in time, only non-Custom setup scripts
              -- are supported.  Implementing per-component builds with
              -- Custom would require us to create a new 'ElabSetup'
              -- type, and teach all of the code paths how to handle it.
              -- Once you've implemented this, swap it for the code below.
              cuz_custom =
                  case PD.buildType (elabPkgDescription elab0) of
                      Nothing        -> cuz "build-type is not specified"
                      Just PD.Custom -> cuz "build-type is Custom"
                      Just _         -> []
              -- cabal-format versions prior to 1.8 have different build-depends semantics
              -- for now it's easier to just fallback to legacy-mode when specVersion < 1.8
              -- see, https://github.com/haskell/cabal/issues/4121
              cuz_spec
                  | PD.specVersion pd >= mkVersion [1,8] = []
                  | otherwise = cuz "cabal-version is less than 1.8"
              -- In the odd corner case that a package has no components at all
              -- then keep it as a whole package, since otherwise it turns into
              -- 0 component graph nodes and effectively vanishes. We want to
              -- keep it around at least for error reporting purposes.
              cuz_length
                  | length g > 0 = []
                  | otherwise    = cuz "there are no buildable components"
              -- For ease of testing, we let per-component builds be toggled
              -- at the top level
              cuz_flag
                  | fromFlagOrDefault True (projectConfigPerComponent sharedPackageConfig)
                  = []
                  | otherwise = cuz "you passed --disable-per-component"
  
          -- | Sometimes a package may make use of features which are only
          -- supported in per-package mode.  If this is the case, we should
          -- give an error when this occurs.
          checkPerPackageOk comps reasons = do
              let is_sublib (CSubLibName _) = True
                  is_sublib _ = False
              when (any (matchElabPkg is_sublib) comps) $
                  dieProgress $
                      text "Internal libraries only supported with per-component builds." $$
                      text "Per-component builds were disabled because" <+>
                          fsep (punctuate comma reasons)
              -- TODO: Maybe exclude Backpack too
  
          elab0 = elaborateSolverToCommon mapDep spkg
          pkgid = elabPkgSourceId    elab0
          pd    = elabPkgDescription elab0
  
          -- TODO: This is just a skeleton to get elaborateSolverToPackage
          -- working correctly
          -- TODO: When we actually support building these components, we
          -- have to add dependencies on this from all other components
          setupComponent :: Maybe ElaboratedConfiguredPackage
          setupComponent
              | fromMaybe PD.Custom (PD.buildType (elabPkgDescription elab0)) == PD.Custom
              = Just elab0 {
                  elabModuleShape = emptyModuleShape,
                  elabUnitId = notImpl "elabUnitId",
                  elabComponentId = notImpl "elabComponentId",
                  elabLinkedInstantiatedWith = Map.empty,
                  elabInstallDirs = notImpl "elabInstallDirs",
                  elabPkgOrComp = ElabComponent (ElaboratedComponent {..})
                }
              | otherwise
              = Nothing
            where
              compSolverName      = CD.ComponentSetup
              compComponentName   = Nothing
              dep_pkgs = elaborateLibSolverId mapDep =<< CD.setupDeps deps0
              compLibDependencies
                  = map configuredId dep_pkgs
              compLinkedLibDependencies = notImpl "compLinkedLibDependencies"
              compOrderLibDependencies = notImpl "compOrderLibDependencies"
              -- Not supported:
              compExeDependencies         = []
              compExeDependencyPaths      = []
              compPkgConfigDependencies   = []
  
              notImpl f =
                  error $ "Distribution.Client.ProjectPlanning.setupComponent: " ++
                          f ++ " not implemented yet"
  
  
          buildComponent
              :: (ConfiguredComponentMap,
                  LinkedComponentMap,
                  Map ComponentId FilePath)
              -> Cabal.Component
              -> LogProgress
                  ((ConfiguredComponentMap,
                    LinkedComponentMap,
                    Map ComponentId FilePath),
                  ElaboratedConfiguredPackage)
          buildComponent (cc_map, lc_map, exe_map) comp =
            addProgressCtx (text "In the stanza" <+>
                            quotes (text (componentNameStanza cname))) $ do
  
              -- 1. Configure the component, but with a place holder ComponentId.
              cc0 <- toConfiguredComponent pd
                      (error "Distribution.Client.ProjectPlanning.cc_cid: filled in later")
                      (Map.unionWith Map.union external_cc_map cc_map) comp
  
              -- 2. Read out the dependencies from the ConfiguredComponent cc0
              let compLibDependencies =
                      -- Nub because includes can show up multiple times
                      ordNub (map (annotatedIdToConfiguredId . ci_ann_id)
                                  (cc_includes cc0))
                  compExeDependencies =
                      map annotatedIdToConfiguredId
                          (cc_exe_deps cc0)
                  compExeDependencyPaths =
                      [ (annotatedIdToConfiguredId aid', path)
                      | aid' <- cc_exe_deps cc0
                      , Just path <- [Map.lookup (ann_id aid') exe_map1]]
                  elab_comp = ElaboratedComponent {..}
  
              -- 3. Construct a preliminary ElaboratedConfiguredPackage,
              -- and use this to compute the component ID.  Fix up cc_id
              -- correctly.
              let elab1 = elab0 {
                          elabPkgOrComp = ElabComponent $ elab_comp
                       }
                  cid = case elabBuildStyle elab0 of
                          BuildInplaceOnly ->
                            mkComponentId $
                              display pkgid ++ "-inplace" ++
                                (case Cabal.componentNameString cname of
                                    Nothing -> ""
                                    Just s -> "-" ++ display s)
                          BuildAndInstall ->
                            hashedInstalledPackageId
                              (packageHashInputs
                                  elaboratedSharedConfig
                                  elab1) -- knot tied
                  cc = cc0 { cc_ann_id = fmap (const cid) (cc_ann_id cc0) }
              infoProgress $ dispConfiguredComponent cc
  
              -- 4. Perform mix-in linking
              let lookup_uid def_uid =
                      case Map.lookup (unDefUnitId def_uid) preexistingInstantiatedPkgs of
                          Just full -> full
                          Nothing -> error ("lookup_uid: " ++ display def_uid)
              lc <- toLinkedComponent verbosity lookup_uid (elabPkgSourceId elab0)
                          (Map.union external_lc_map lc_map) cc
              infoProgress $ dispLinkedComponent lc
              -- NB: elab is setup to be the correct form for an
              -- indefinite library, or a definite library with no holes.
              -- We will modify it in 'instantiateInstallPlan' to handle
              -- instantiated packages.
  
              -- 5. Construct the final ElaboratedConfiguredPackage
              let
                  elab = elab1 {
                      elabModuleShape = lc_shape lc,
                      elabUnitId      = abstractUnitId (lc_uid lc),
                      elabComponentId = lc_cid lc,
                      elabLinkedInstantiatedWith = Map.fromList (lc_insts lc),
                      elabPkgOrComp = ElabComponent $ elab_comp {
                          compLinkedLibDependencies = ordNub (map ci_id (lc_includes lc)),
                          compOrderLibDependencies =
                            ordNub (map (abstractUnitId . ci_id)
                                        (lc_includes lc ++ lc_sig_includes lc))
                        },
                      elabInstallDirs = install_dirs cid
                     }
  
              -- 6. Construct the updated local maps
              let cc_map'  = extendConfiguredComponentMap cc cc_map
                  lc_map'  = extendLinkedComponentMap lc lc_map
                  exe_map' = Map.insert cid (inplace_bin_dir elab) exe_map
  
              return ((cc_map', lc_map', exe_map'), elab)
            where
              compLinkedLibDependencies = error "buildComponent: compLinkedLibDependencies"
              compOrderLibDependencies = error "buildComponent: compOrderLibDependencies"
  
              cname = Cabal.componentName comp
              compComponentName = Just cname
              compSolverName = CD.componentNameToComponent cname
  
              -- NB: compLinkedLibDependencies and
              -- compOrderLibDependencies are defined when we define
              -- 'elab'.
              external_lib_dep_sids = CD.select (== compSolverName) deps0
              external_exe_dep_sids = CD.select (== compSolverName) exe_deps0
              -- TODO: The fact that lib SolverIds and exe SolverIds are
              -- jammed together here means that we're losing information!
              external_dep_sids = external_lib_dep_sids ++ external_exe_dep_sids
              external_dep_pkgs = concatMap mapDep external_dep_sids
  
              external_exe_map = Map.fromList $
                  [ (getComponentId pkg, path)
                  | pkg <- external_dep_pkgs
                  , Just path <- [planPackageExePath pkg] ]
              exe_map1 = Map.union external_exe_map exe_map
  
              external_cc_map = Map.fromListWith Map.union
                              $ map mkCCMapping external_dep_pkgs
              external_lc_map = Map.fromList (map mkShapeMapping external_dep_pkgs)
  
              compPkgConfigDependencies =
                  [ (pn, fromMaybe (error $ "compPkgConfigDependencies: impossible! "
                                              ++ display pn ++ " from "
                                              ++ display (elabPkgSourceId elab0))
                                   (pkgConfigDbPkgVersion pkgConfigDB pn))
                  | PkgconfigDependency pn _ <- PD.pkgconfigDepends
                                                  (Cabal.componentBuildInfo comp) ]
  
              install_dirs cid
                | shouldBuildInplaceOnly spkg
                -- use the ordinary default install dirs
                = (InstallDirs.absoluteInstallDirs
                     pkgid
                     (newSimpleUnitId cid)
                     (compilerInfo compiler)
                     InstallDirs.NoCopyDest
                     platform
                     defaultInstallDirs) {
  
                    InstallDirs.libsubdir  = "", -- absoluteInstallDirs sets these as
                    InstallDirs.datasubdir = ""  -- 'undefined' but we have to use
                  }                              -- them as "Setup.hs configure" args
  
                | otherwise
                -- use special simplified install dirs
                = storePackageInstallDirs
                    storeDirLayout
                    (compilerId compiler)
                    cid
  
              inplace_bin_dir elab =
                  binDirectoryFor
                      distDirLayout
                      elaboratedSharedConfig
                      elab $
                      case Cabal.componentNameString cname of
                               Just n -> display n
                               Nothing -> ""
  
  
      -- | Given a 'SolverId' referencing a dependency on a library, return
      -- the 'ElaboratedPlanPackage' corresponding to the library.  This
      -- returns at most one result.
      elaborateLibSolverId :: (SolverId -> [ElaboratedPlanPackage])
                           -> SolverId -> [ElaboratedPlanPackage]
      elaborateLibSolverId mapDep = filter (matchPlanPkg (== CLibName)) . mapDep
  
      -- | Given an 'ElaboratedPlanPackage', return the path to where the
      -- executable that this package represents would be installed.
      planPackageExePath :: ElaboratedPlanPackage -> Maybe FilePath
      planPackageExePath =
          -- Pre-existing executables are assumed to be in PATH
          -- already.  In fact, this should be impossible.
          InstallPlan.foldPlanPackage (const Nothing) $ \elab -> Just $
              binDirectoryFor
                  distDirLayout
                  elaboratedSharedConfig
                  elab $
                      case elabPkgOrComp elab of
                          ElabPackage _ -> ""
                          ElabComponent comp ->
                              case fmap Cabal.componentNameString
                                        (compComponentName comp) of
                                  Just (Just n) -> display n
                                  _ -> ""
  
      elaborateSolverToPackage :: (SolverId -> [ElaboratedPlanPackage])
                               -> SolverPackage UnresolvedPkgLoc
                               -> ComponentsGraph
                               -> [ElaboratedConfiguredPackage]
                               -> ElaboratedConfiguredPackage
      elaborateSolverToPackage
          mapDep
          pkg@(SolverPackage (SourcePackage pkgid _gdesc _srcloc _descOverride _patch)
                             _flags _stanzas _deps0 _exe_deps0) compGraph comps =
          -- Knot tying: the final elab includes the
          -- pkgInstalledId, which is calculated by hashing many
          -- of the other fields of the elaboratedPackage.
          elab
        where
          elab0@ElaboratedConfiguredPackage{..} = elaborateSolverToCommon mapDep pkg
          elab = elab0 {
                  elabUnitId = newSimpleUnitId pkgInstalledId,
                  elabComponentId = pkgInstalledId,
                  elabLinkedInstantiatedWith = Map.empty,
                  elabInstallDirs = install_dirs,
                  elabPkgOrComp = ElabPackage $ ElaboratedPackage {..},
                  elabModuleShape = modShape
              }
  
          modShape = case find (matchElabPkg (== CLibName)) comps of
                          Nothing -> emptyModuleShape
                          Just e -> Ty.elabModuleShape e
  
          pkgInstalledId
            | shouldBuildInplaceOnly pkg
            = mkComponentId (display pkgid ++ "-inplace")
  
            | otherwise
            = assert (isJust elabPkgSourceHash) $
              hashedInstalledPackageId
                (packageHashInputs
                  elaboratedSharedConfig
                  elab)  -- recursive use of elab
  
            | otherwise
            = error $ "elaborateInstallPlan: non-inplace package "
                   ++ " is missing a source hash: " ++ display pkgid
  
          -- Need to filter out internal dependencies, because they don't
          -- correspond to anything real anymore.
          isExt confid = confSrcId confid /= pkgid
          filterExt  = filter isExt
          filterExt' = filter (isExt . fst)
  
          pkgLibDependencies
              = buildComponentDeps (filterExt  . compLibDependencies)
          pkgExeDependencies
              = buildComponentDeps (filterExt  . compExeDependencies)
          pkgExeDependencyPaths
              = buildComponentDeps (filterExt' . compExeDependencyPaths)
          -- TODO: Why is this flat?
          pkgPkgConfigDependencies
              = CD.flatDeps $ buildComponentDeps compPkgConfigDependencies
  
          pkgDependsOnSelfLib
               = CD.fromList [ (CD.componentNameToComponent cn, [()])
                            | Graph.N _ cn _ <- fromMaybe [] mb_closure ]
            where
              mb_closure = Graph.revClosure compGraph [ k | k <- Graph.keys compGraph, is_lib k ]
              is_lib CLibName = True
              -- NB: this case should not occur, because sub-libraries
              -- are not supported without per-component builds
              is_lib (CSubLibName _) = True
              is_lib _ = False
  
          buildComponentDeps f
              = CD.fromList [ (compSolverName comp, f comp)
                            | ElaboratedConfiguredPackage{
                                  elabPkgOrComp = ElabComponent comp
                              } <- comps
                            ]
  
          -- Filled in later
          pkgStanzasEnabled  = Set.empty
  
          install_dirs
            | shouldBuildInplaceOnly pkg
            -- use the ordinary default install dirs
            = (InstallDirs.absoluteInstallDirs
                 pkgid
                 (newSimpleUnitId pkgInstalledId)
                 (compilerInfo compiler)
                 InstallDirs.NoCopyDest
                 platform
                 defaultInstallDirs) {
  
                InstallDirs.libsubdir  = "", -- absoluteInstallDirs sets these as
                InstallDirs.datasubdir = ""  -- 'undefined' but we have to use
              }                              -- them as "Setup.hs configure" args
  
            | otherwise
            -- use special simplified install dirs
            = storePackageInstallDirs
                storeDirLayout
                (compilerId compiler)
                pkgInstalledId
  
      elaborateSolverToCommon :: (SolverId -> [ElaboratedPlanPackage])
                              -> SolverPackage UnresolvedPkgLoc
                              -> ElaboratedConfiguredPackage
      elaborateSolverToCommon mapDep
          pkg@(SolverPackage spkg@(SourcePackage pkgid gdesc srcloc descOverride _patch)
                             flags stanzas deps0 _exe_deps0) =
          elaboratedPackage
        where
          elaboratedPackage = ElaboratedConfiguredPackage {..}
  
          -- These get filled in later
          elabUnitId          = error "elaborateSolverToCommon: elabUnitId"
          elabComponentId     = error "elaborateSolverToCommon: elabComponentId"
          elabInstantiatedWith = Map.empty
          elabLinkedInstantiatedWith = error "elaborateSolverToCommon: elabLinkedInstantiatedWith"
          elabPkgOrComp       = error "elaborateSolverToCommon: elabPkgOrComp"
          elabInstallDirs     = error "elaborateSolverToCommon: elabInstallDirs"
          elabModuleShape     = error "elaborateSolverToCommon: elabModuleShape"
  
          elabIsCanonical     = True
          elabPkgSourceId     = pkgid
          elabPkgDescription  = let Right (desc, _) =
                                      PD.finalizePD
                                      flags elabEnabledSpec (const True)
                                      platform (compilerInfo compiler)
                                      [] gdesc
                                 in desc
  
          _elabPatchFiles = sourcePackagePatches spkg
          elabFlagAssignment  = flags
          elabFlagDefaults    = [ (Cabal.flagName flag, Cabal.flagDefault flag)
                                | flag <- PD.genPackageFlags gdesc ]
  
          elabEnabledSpec      = enableStanzas stanzas
          elabStanzasAvailable = Set.fromList stanzas
          elabStanzasRequested =
              -- NB: even if a package stanza is requested, if the package
              -- doesn't actually have any of that stanza we omit it from
              -- the request, to ensure that we don't decide that this
              -- package needs to be rebuilt.  (It needs to be done here,
              -- because the ElaboratedConfiguredPackage is where we test
              -- whether or not there have been changes.)
              Map.fromList $ [ (TestStanzas,  v) | v <- maybeToList tests
                                                 , _ <- PD.testSuites elabPkgDescription ]
                          ++ [ (BenchStanzas, v) | v <- maybeToList benchmarks
                                                 , _ <- PD.benchmarks elabPkgDescription ]
            where
              tests, benchmarks :: Maybe Bool
              tests      = perPkgOptionMaybe pkgid packageConfigTests
              benchmarks = perPkgOptionMaybe pkgid packageConfigBenchmarks
  
          -- This is a placeholder which will get updated by 'pruneInstallPlanPass1'
          -- and 'pruneInstallPlanPass2'.  We can't populate it here
          -- because whether or not tests/benchmarks should be enabled
          -- is heuristically calculated based on whether or not the
          -- dependencies of the test suite have already been installed,
          -- but this function doesn't know what is installed (since
          -- we haven't improved the plan yet), so we do it in another pass.
          -- Check the comments of those functions for more details.
          elabBuildTargets    = []
          elabTestTargets     = []
          elabBenchTargets    = []
          elabReplTarget      = Nothing
          elabBuildHaddocks   =
            perPkgOptionFlag pkgid False packageConfigDocumentation
  
          elabPkgSourceLocation = srcloc
          elabPkgSourceHash   = Map.lookup pkgid sourcePackageHashes
          elabLocalToProject  = isLocalToProject pkg
          elabBuildStyle      = if shouldBuildInplaceOnly pkg
                                  then BuildInplaceOnly else BuildAndInstall
          elabBuildPackageDBStack    = buildAndRegisterDbs
          elabRegisterPackageDBStack = buildAndRegisterDbs
  
          elabSetupScriptStyle       = packageSetupScriptStyle elabPkgDescription
          -- Computing the deps here is a little awful
          deps = fmap (concatMap (elaborateLibSolverId mapDep)) deps0
          elabSetupScriptCliVersion  = packageSetupScriptSpecVersion
                                        elabSetupScriptStyle elabPkgDescription deps
          elabSetupPackageDBStack    = buildAndRegisterDbs
  
          buildAndRegisterDbs
            | shouldBuildInplaceOnly pkg = inplacePackageDbs
            | otherwise                  = storePackageDbs
  
          elabPkgDescriptionOverride = descOverride
  
          elabVanillaLib    = perPkgOptionFlag pkgid False packageConfigVanillaLib --TODO: [required feature]: also needs to be handled recursively
          elabSharedLib     = pkgid `Set.member` pkgsUseSharedLibrary
          elabDynExe        = perPkgOptionFlag pkgid True packageConfigDynExe
          elabGHCiLib       = perPkgOptionFlag pkgid False packageConfigGHCiLib --TODO: [required feature] needs to default to enabled on windows still
  
          elabProfExe       = perPkgOptionFlag pkgid False packageConfigProf
          elabProfLib       = pkgid `Set.member` pkgsUseProfilingLibrary
          elabVerifyMode    = perPkgOptionFlag pkgid False packageConfigVerifyMode
  
          (elabProfExeDetail,
           elabProfLibDetail) = perPkgOptionLibExeFlag pkgid ProfDetailDefault
                                 packageConfigProfDetail
                                 packageConfigProfLibDetail
          elabCoverage      = perPkgOptionFlag pkgid False packageConfigCoverage
  
          elabOptimization  = perPkgOptionFlag pkgid NormalOptimisation packageConfigOptimization
          elabSplitObjs     = perPkgOptionFlag pkgid False packageConfigSplitObjs
          elabStripLibs     = perPkgOptionFlag pkgid False packageConfigStripLibs
          elabStripExes     = perPkgOptionFlag pkgid False packageConfigStripExes
          elabDebugInfo     = perPkgOptionFlag pkgid NormalDebugInfo packageConfigDebugInfo
  
          -- Combine the configured compiler prog settings with the user-supplied
          -- config. For the compiler progs any user-supplied config was taken
          -- into account earlier when configuring the compiler so its ok that
          -- our configured settings for the compiler override the user-supplied
          -- config here.
          elabProgramPaths  = Map.fromList
                               [ (programId prog, programPath prog)
                               | prog <- configuredPrograms compilerprogdb ]
                          <> perPkgOptionMapLast pkgid packageConfigProgramPaths
          elabProgramArgs   = Map.fromList
                               [ (programId prog, args)
                               | prog <- configuredPrograms compilerprogdb
                               , let args = programOverrideArgs prog
                               , not (null args)
                               ]
                          <> perPkgOptionMapMappend pkgid packageConfigProgramArgs
          elabProgramPathExtra    = perPkgOptionNubList pkgid packageConfigProgramPathExtra
          elabConfigureScriptArgs = perPkgOptionList pkgid packageConfigConfigureArgs
          elabExtraLibDirs        = perPkgOptionList pkgid packageConfigExtraLibDirs
          elabExtraFrameworkDirs  = perPkgOptionList pkgid packageConfigExtraFrameworkDirs
          elabExtraIncludeDirs    = perPkgOptionList pkgid packageConfigExtraIncludeDirs
          elabProgPrefix          = perPkgOptionMaybe pkgid packageConfigProgPrefix
          elabProgSuffix          = perPkgOptionMaybe pkgid packageConfigProgSuffix
  
  
          elabHaddockHoogle       = perPkgOptionFlag pkgid False packageConfigHaddockHoogle
          elabHaddockHtml         = perPkgOptionFlag pkgid False packageConfigHaddockHtml
          elabHaddockHtmlLocation = perPkgOptionMaybe pkgid packageConfigHaddockHtmlLocation
          elabHaddockForeignLibs  = perPkgOptionFlag pkgid False packageConfigHaddockForeignLibs
          elabHaddockExecutables  = perPkgOptionFlag pkgid False packageConfigHaddockExecutables
          elabHaddockTestSuites   = perPkgOptionFlag pkgid False packageConfigHaddockTestSuites
          elabHaddockBenchmarks   = perPkgOptionFlag pkgid False packageConfigHaddockBenchmarks
          elabHaddockInternal     = perPkgOptionFlag pkgid False packageConfigHaddockInternal
          elabHaddockCss          = perPkgOptionMaybe pkgid packageConfigHaddockCss
          elabHaddockHscolour     = perPkgOptionFlag pkgid False packageConfigHaddockHscolour
          elabHaddockHscolourCss  = perPkgOptionMaybe pkgid packageConfigHaddockHscolourCss
          elabHaddockContents     = perPkgOptionMaybe pkgid packageConfigHaddockContents
  
      perPkgOptionFlag  :: PackageId -> a ->  (PackageConfig -> Flag a) -> a
      perPkgOptionMaybe :: PackageId ->       (PackageConfig -> Flag a) -> Maybe a
      perPkgOptionList  :: PackageId ->       (PackageConfig -> [a])    -> [a]
  
      perPkgOptionFlag  pkgid def f = fromFlagOrDefault def (lookupPerPkgOption pkgid f)
      perPkgOptionMaybe pkgid     f = flagToMaybe (lookupPerPkgOption pkgid f)
      perPkgOptionList  pkgid     f = lookupPerPkgOption pkgid f
      perPkgOptionNubList    pkgid f = fromNubList   (lookupPerPkgOption pkgid f)
      perPkgOptionMapLast    pkgid f = getMapLast    (lookupPerPkgOption pkgid f)
      perPkgOptionMapMappend pkgid f = getMapMappend (lookupPerPkgOption pkgid f)
  
      perPkgOptionLibExeFlag pkgid def fboth flib = (exe, lib)
        where
          exe = fromFlagOrDefault def bothflag
          lib = fromFlagOrDefault def (bothflag <> libflag)
  
          bothflag = lookupPerPkgOption pkgid fboth
          libflag  = lookupPerPkgOption pkgid flib
  
      lookupPerPkgOption :: (Package pkg, Monoid m)
                         => pkg -> (PackageConfig -> m) -> m
      lookupPerPkgOption pkg f =
          -- This is where we merge the options from the project config that
          -- apply to all packages, all project local packages, and to specific
          -- named packages
          global `mappend` local `mappend` perpkg
        where
          global = f allPackagesConfig
          local  | isLocalToProject pkg
                 = f localPackagesConfig
                 | otherwise
                 = mempty
          perpkg = maybe mempty f (Map.lookup (packageName pkg) perPackageConfig)
  
      inplacePackageDbs = storePackageDbs
                       ++ [distPackageDB (compilerId compiler)]
                       ++ (catMaybes $ projectConfigPackageDBs sharedPackageConfig)
  
      storePackageDbs   = storePackageDBStack (compilerId compiler)
  
      -- For this local build policy, every package that lives in a local source
      -- dir (as opposed to a tarball), or depends on such a package, will be
      -- built inplace into a shared dist dir. Tarball packages that depend on
      -- source dir packages will also get unpacked locally.
      shouldBuildInplaceOnly :: SolverPackage loc -> Bool
      shouldBuildInplaceOnly pkg = Set.member (packageId pkg)
                                              pkgsToBuildInplaceOnly
  
      pkgsToBuildInplaceOnly :: Set PackageId
      pkgsToBuildInplaceOnly =
          Set.fromList
        $ map packageId
        $ SolverInstallPlan.reverseDependencyClosure
            solverPlan
           (map PlannedId (Set.toList pkgsLocalToProject))
  
      isLocalToProject :: Package pkg => pkg -> Bool
      isLocalToProject pkg = Set.member (packageId pkg)
                                        pkgsLocalToProject
  
      pkgsLocalToProject :: Set PackageId
      pkgsLocalToProject =
          Set.fromList (catMaybes (map shouldBeLocal localPackages))
          --TODO: localPackages is a misnomer, it's all project packages
          -- here is where we decide which ones will be local!
        where
          shouldBeLocal :: PackageSpecifier UnresolvedSourcePackage -> Maybe PackageId
          shouldBeLocal NamedPackage{}              = Nothing
          shouldBeLocal (SpecificSourcePackage pkg)
            | ScmPackage _ sourceRepos _ _ <- packageSource pkg
            , all isExactRepo sourceRepos
            = Nothing
            | otherwise = Just (packageId pkg)
          -- TODO: It's not actually obvious for all of the
          -- 'ProjectPackageLocation's that they should all be local. We might
          -- need to provide the user with a choice.
          -- Also, review use of SourcePackage's loc vs ProjectPackageLocation
  
      pkgsUseSharedLibrary :: Set PackageId
      pkgsUseSharedLibrary =
          packagesWithLibDepsDownwardClosedProperty needsSharedLib
        where
          needsSharedLib pkg =
              fromMaybe compilerShouldUseSharedLibByDefault
                        (liftM2 (||) pkgSharedLib pkgDynExe)
            where
              pkgid        = packageId pkg
              pkgSharedLib = perPkgOptionMaybe pkgid packageConfigSharedLib
              pkgDynExe    = perPkgOptionMaybe pkgid packageConfigDynExe
  
      --TODO: [code cleanup] move this into the Cabal lib. It's currently open
      -- coded in Distribution.Simple.Configure, but should be made a proper
      -- function of the Compiler or CompilerInfo.
      compilerShouldUseSharedLibByDefault =
        case compilerFlavor compiler of
          GHC   -> GHC.isDynamic compiler
          GHCJS -> GHCJS.isDynamic compiler
          Eta   -> Eta.isDynamic compiler
          _     -> False
  
      pkgsUseProfilingLibrary :: Set PackageId
      pkgsUseProfilingLibrary =
          packagesWithLibDepsDownwardClosedProperty needsProfilingLib
        where
          needsProfilingLib pkg =
              fromFlagOrDefault False (profBothFlag <> profLibFlag)
            where
              pkgid        = packageId pkg
              profBothFlag = lookupPerPkgOption pkgid packageConfigProf
              profLibFlag  = lookupPerPkgOption pkgid packageConfigProfLib
              --TODO: [code cleanup] unused: the old deprecated packageConfigProfExe
  
      libDepGraph = Graph.fromDistinctList $
                      map NonSetupLibDepSolverPlanPackage
                          (SolverInstallPlan.toList solverPlan)
  
      packagesWithLibDepsDownwardClosedProperty property =
          Set.fromList
        . map packageId
        . fromMaybe []
        $ Graph.closure
            libDepGraph
            [ Graph.nodeKey pkg
            | pkg <- SolverInstallPlan.toList solverPlan
            , property pkg ] -- just the packages that satisfy the property
        --TODO: [nice to have] this does not check the config consistency,
        -- e.g. a package explicitly turning off profiling, but something
        -- depending on it that needs profiling. This really needs a separate
        -- package config validation/resolution pass.
  
        --TODO: [nice to have] config consistency checking:
        -- + profiling libs & exes, exe needs lib, recursive
        -- + shared libs & exes, exe needs lib, recursive
        -- + vanilla libs & exes, exe needs lib, recursive
        -- + ghci or shared lib needed by TH, recursive, ghc version dependent
  
  -- TODO: Drop matchPlanPkg/matchElabPkg in favor of mkCCMapping
  
  -- | Given a 'ElaboratedPlanPackage', report if it matches a 'ComponentName'.
  matchPlanPkg :: (ComponentName -> Bool) -> ElaboratedPlanPackage -> Bool
  matchPlanPkg p = InstallPlan.foldPlanPackage (p . ipiComponentName) (matchElabPkg p)
  
  -- | Get the appropriate 'ComponentName' which identifies an installed
  -- component.
  ipiComponentName :: IPI.InstalledPackageInfo -> ComponentName
  ipiComponentName ipkg =
      case IPI.sourceLibName ipkg of
          Nothing -> CLibName
          Just n  -> (CSubLibName n)
  
  -- | Given a 'ElaboratedConfiguredPackage', report if it matches a
  -- 'ComponentName'.
  matchElabPkg :: (ComponentName -> Bool) -> ElaboratedConfiguredPackage -> Bool
  matchElabPkg p elab =
      case elabPkgOrComp elab of
          ElabComponent comp -> maybe False p (compComponentName comp)
          ElabPackage _ ->
              -- So, what should we do here?  One possibility is to
              -- unconditionally return 'True', because whatever it is
              -- that we're looking for, it better be in this package.
              -- But this is a bit dodgy if the package doesn't actually
              -- have, e.g., a library.  Fortunately, it's not possible
              -- for the build of the library/executables to be toggled
              -- by 'pkgStanzasEnabled', so the only thing we have to
              -- test is if the component in question is *buildable.*
              any (p . componentName)
                  (Cabal.pkgBuildableComponents (elabPkgDescription elab))
  
  -- | Given an 'ElaboratedPlanPackage', generate the mapping from 'PackageName'
  -- and 'ComponentName' to the 'ComponentId' that that should be used
  -- in this case.
  mkCCMapping :: ElaboratedPlanPackage
              -> (PackageName, Map ComponentName (AnnotatedId ComponentId))
  mkCCMapping =
      InstallPlan.foldPlanPackage
         (\ipkg -> (packageName ipkg,
                      Map.singleton (ipiComponentName ipkg)
                                    -- TODO: libify
                                    (AnnotatedId {
                                      ann_id = IPI.installedComponentId ipkg,
                                      ann_pid = packageId ipkg,
                                      ann_cname = IPI.sourceComponentName ipkg
                                    })))
        $ \elab ->
          let mk_aid cn = AnnotatedId {
                              ann_id = elabComponentId elab,
                              ann_pid = packageId elab,
                              ann_cname = cn
                          }
          in (packageName elab,
              case elabPkgOrComp elab of
                  ElabComponent comp ->
                      case compComponentName comp of
                          Nothing -> Map.empty
                          Just n  -> Map.singleton n (mk_aid n)
                  ElabPackage _ ->
                      Map.fromList $
                          map (\comp -> let cn = Cabal.componentName comp in (cn, mk_aid cn))
                              (Cabal.pkgBuildableComponents (elabPkgDescription elab)))
  
  -- | Given an 'ElaboratedPlanPackage', generate the mapping from 'ComponentId'
  -- to the shape of this package, as per mix-in linking.
  mkShapeMapping :: ElaboratedPlanPackage
                 -> (ComponentId, (OpenUnitId, ModuleShape))
  mkShapeMapping dpkg =
      (getComponentId dpkg, (indef_uid, shape))
    where
      (dcid, shape) =
          InstallPlan.foldPlanPackage
              -- Uses Monad (->)
              (liftM2 (,) IPI.installedComponentId shapeInstalledPackage)
              (liftM2 (,) elabComponentId elabModuleShape)
              dpkg
      indef_uid =
          IndefFullUnitId dcid
              (Map.fromList [ (req, OpenModuleVar req)
                            | req <- Set.toList (modShapeRequires shape)])
  
  -- | Get the bin\/ directories that a package's executables should reside in.
  --
  -- The result may be empty if the package does not build any executables.
  --
  -- The result may have several entries if this is an inplace build of a package
  -- with multiple executables.
  binDirectories
    :: DistDirLayout
    -> ElaboratedSharedConfig
    -> ElaboratedConfiguredPackage
    -> [FilePath]
  binDirectories layout config package = case elabBuildStyle package of
    -- quick sanity check: no sense returning a bin directory if we're not going
    -- to put any executables in it, that will just clog up the PATH
    _ | noExecutables -> []
    BuildAndInstall -> [installedBinDirectory package]
    BuildInplaceOnly -> map (root</>) $ case elabPkgOrComp package of
      ElabComponent comp -> case compSolverName comp of
        CD.ComponentExe n -> [display n]
        _ -> []
      ElabPackage _ -> map (display . PD.exeName)
                     . PD.executables
                     . elabPkgDescription
                     $ package
    where
    noExecutables = null . PD.executables . elabPkgDescription $ package
    root  =  distBuildDirectory layout (elabDistDirParams config package)
         </> "build"
  
  -- | A newtype for 'SolverInstallPlan.SolverPlanPackage' for which the
  -- dependency graph considers only dependencies on libraries which are
  -- NOT from setup dependencies.  Used to compute the set
  -- of packages needed for profiling and dynamic libraries.
  newtype NonSetupLibDepSolverPlanPackage
      = NonSetupLibDepSolverPlanPackage
      { unNonSetupLibDepSolverPlanPackage :: SolverInstallPlan.SolverPlanPackage }
  
  instance Package NonSetupLibDepSolverPlanPackage where
      packageId = packageId . unNonSetupLibDepSolverPlanPackage
  
  instance IsNode NonSetupLibDepSolverPlanPackage where
      type Key NonSetupLibDepSolverPlanPackage = SolverId
      nodeKey = nodeKey . unNonSetupLibDepSolverPlanPackage
      nodeNeighbors (NonSetupLibDepSolverPlanPackage spkg)
          = ordNub $ CD.nonSetupDeps (resolverPackageLibDeps spkg)
  
  type InstS = Map UnitId ElaboratedPlanPackage
  type InstM a = State InstS a
  
  getComponentId :: ElaboratedPlanPackage
                 -> ComponentId
  getComponentId (InstallPlan.PreExisting dipkg) = IPI.installedComponentId dipkg
  getComponentId (InstallPlan.Configured elab) = elabComponentId elab
  getComponentId (InstallPlan.Installed elab) = elabComponentId elab
  
  instantiateInstallPlan :: ElaboratedInstallPlan -> ElaboratedInstallPlan
  instantiateInstallPlan plan =
      InstallPlan.new (IndependentGoals False)
                      (Graph.fromDistinctList (Map.elems ready_map))
    where
      pkgs = InstallPlan.toList plan
  
      cmap = Map.fromList [ (getComponentId pkg, pkg) | pkg <- pkgs ]
  
      instantiateUnitId :: ComponentId -> Map ModuleName Module
                        -> InstM DefUnitId
      instantiateUnitId cid insts = state $ \s ->
          case Map.lookup uid s of
              Nothing ->
                  -- Knot tied
                  let (r, s') = runState (instantiateComponent uid cid insts)
                                         (Map.insert uid r s)
                  in (def_uid, Map.insert uid r s')
              Just _ -> (def_uid, s)
        where
          def_uid = mkDefUnitId cid insts
          uid = unDefUnitId def_uid
  
      instantiateComponent
          :: UnitId -> ComponentId -> Map ModuleName Module
          -> InstM ElaboratedPlanPackage
      instantiateComponent uid cid insts
        | Just planpkg <- Map.lookup cid cmap
        = case planpkg of
            InstallPlan.Configured (elab@ElaboratedConfiguredPackage
                                      { elabPkgOrComp = ElabComponent comp }) -> do
              deps <- mapM (substUnitId insts)
                           (compLinkedLibDependencies comp)
              let getDep (Module dep_uid _) = [dep_uid]
              return $ InstallPlan.Configured elab {
                      elabUnitId = uid,
                      elabComponentId = cid,
                      elabInstantiatedWith = insts,
                      elabIsCanonical = Map.null insts,
                      elabPkgOrComp = ElabComponent comp {
                          compOrderLibDependencies =
                              (if Map.null insts then [] else [newSimpleUnitId cid]) ++
                              ordNub (map unDefUnitId
                                  (deps ++ concatMap getDep (Map.elems insts)))
                      }
                  }
            _ -> return planpkg
        | otherwise = error ("instantiateComponent: " ++ display cid)
  
      substUnitId :: Map ModuleName Module -> OpenUnitId -> InstM DefUnitId
      substUnitId _ (DefiniteUnitId uid) =
          return uid
      substUnitId subst (IndefFullUnitId cid insts) = do
          insts' <- substSubst subst insts
          instantiateUnitId cid insts'
  
      -- NB: NOT composition
      substSubst :: Map ModuleName Module
                 -> Map ModuleName OpenModule
                 -> InstM (Map ModuleName Module)
      substSubst subst insts = T.mapM (substModule subst) insts
  
      substModule :: Map ModuleName Module -> OpenModule -> InstM Module
      substModule subst (OpenModuleVar mod_name)
          | Just m <- Map.lookup mod_name subst = return m
          | otherwise = error "substModule: non-closing substitution"
      substModule subst (OpenModule uid mod_name) = do
          uid' <- substUnitId subst uid
          return (Module uid' mod_name)
  
      indefiniteUnitId :: ComponentId -> InstM UnitId
      indefiniteUnitId cid = do
          let uid = newSimpleUnitId cid
          r <- indefiniteComponent uid cid
          state $ \s -> (uid, Map.insert uid r s)
  
      indefiniteComponent :: UnitId -> ComponentId -> InstM ElaboratedPlanPackage
      indefiniteComponent _uid cid
        | Just planpkg <- Map.lookup cid cmap
        = return planpkg
        | otherwise = error ("indefiniteComponent: " ++ display cid)
  
      ready_map = execState work Map.empty
  
      work = forM_ pkgs $ \pkg ->
              case pkg of
                  InstallPlan.Configured elab
                      | not (Map.null (elabLinkedInstantiatedWith elab))
                      -> indefiniteUnitId (elabComponentId elab)
                          >> return ()
                  _ -> instantiateUnitId (getComponentId pkg) Map.empty
                          >> return ()
  
  ---------------------------
  -- Build targets
  --
  
  -- | Refer to ProjectPlanning.Types for details of these important types:
  --
  -- data ComponentTarget = ...
  -- data SubComponentTarget = ...
  --
  -- One step in the build system is to translate higher level intentions like
  -- "build this package", "test that package", or "repl that component" into
  -- a more detailed specification of exactly which components to build (or other
  -- actions like repl or build docs). This translation is somewhat different for
  -- different commands. For example "test" for a package will build a different
  -- set of components than "build". In addition, the translation of these
  -- intentions can fail. For example "run" for a package is only unambiguous
  -- when the package has a single executable.
  --
  -- So we need a little bit of infrastructure to make it easy for the command
  -- implementations to select what component targets are meant when a user asks
  -- to do something with a package or component. To do this (and to be able to
  -- produce good error messages for mistakes and when targets are not available)
  -- we need to gather and summarise accurate information about all the possible
  -- targets, both available and unavailable. Then a command implementation can
  -- decide which of the available component targets should be selected.
  
  -- | An available target represents a component within a package that a user
  -- command could plausibly refer to. In this sense, all the components defined
  -- within the package are things the user could refer to, whether or not it
  -- would actually be possible to build that component.
  --
  -- In particular the available target contains an 'AvailableTargetStatus' which
  -- informs us about whether it's actually possible to select this component to
  -- be built, and if not why not. This detail makes it possible for command
  -- implementations (like @build@, @test@ etc) to accurately report why a target
  -- cannot be used.
  --
  -- Note that the type parameter is used to help enforce that command
  -- implementations can only select targets that can actually be built (by
  -- forcing them to return the @k@ value for the selected targets).
  -- In particular 'resolveTargets' makes use of this (with @k@ as
  -- @('UnitId', ComponentName')@) to identify the targets thus selected.
  --
  data AvailableTarget k = AvailableTarget {
         availableTargetPackageId      :: PackageId,
         availableTargetComponentName  :: ComponentName,
         availableTargetStatus         :: AvailableTargetStatus k,
         availableTargetLocalToProject :: Bool
       }
    deriving (Eq, Show, Functor)
  
  -- | The status of a an 'AvailableTarget' component. This tells us whether
  -- it's actually possible to select this component to be built, and if not
  -- why not.
  --
  data AvailableTargetStatus k =
         TargetDisabledByUser   -- ^ When the user does @tests: False@
       | TargetDisabledBySolver -- ^ When the solver could not enable tests
       | TargetNotBuildable     -- ^ When the component has @buildable: False@
       | TargetNotLocal         -- ^ When the component is non-core in a non-local package
       | TargetBuildable k TargetRequested -- ^ The target can or should be built
    deriving (Eq, Ord, Show, Functor)
  
  -- | This tells us whether a target ought to be built by default, or only if
  -- specifically requested. The policy is that components like libraries and
  -- executables are built by default by @build@, but test suites and benchmarks
  -- are not, unless this is overridden in the project configuration.
  --
  data TargetRequested =
         TargetRequestedByDefault    -- ^ To be built by default
       | TargetNotRequestedByDefault -- ^ Not to be built by default
    deriving (Eq, Ord, Show)
  
  -- | Given the install plan, produce the set of 'AvailableTarget's for each
  -- package-component pair.
  --
  -- Typically there will only be one such target for each component, but for
  -- example if we have a plan with both normal and profiling variants of a
  -- component then we would get both as available targets, or similarly if we
  -- had a plan that contained two instances of the same version of a package.
  -- This approach makes it relatively easy to select all instances\/variants
  -- of a component.
  --
  availableTargets :: ElaboratedInstallPlan
                   -> Map (PackageId, ComponentName)
                          [AvailableTarget (UnitId, ComponentName)]
  availableTargets installPlan =
      let rs = [ (pkgid, cname, fake, target)
               | pkg <- InstallPlan.toList installPlan
               , (pkgid, cname, fake, target) <- case pkg of
                   InstallPlan.PreExisting ipkg -> availableInstalledTargets ipkg
                   InstallPlan.Installed   elab -> availableSourceTargets elab
                   InstallPlan.Configured  elab -> availableSourceTargets elab
               ]
       in Map.union
           (Map.fromListWith (++)
              [ ((pkgid, cname), [target])
              | (pkgid, cname, fake, target) <- rs, not fake])
           (Map.fromList
              [ ((pkgid, cname), [target])
              | (pkgid, cname, fake, target) <- rs, fake])
      -- The normal targets mask the fake ones. We get all instances of the
      -- normal ones and only one copy of the fake ones (as there are many
      -- duplicates of the fake ones). See 'availableSourceTargets' below for
      -- more details on this fake stuff is about.
  
  availableInstalledTargets :: IPI.InstalledPackageInfo
                            -> [(PackageId, ComponentName, Bool,
                                 AvailableTarget (UnitId, ComponentName))]
  availableInstalledTargets ipkg =
      let unitid = installedUnitId ipkg
          cname  = CLibName
          status = TargetBuildable (unitid, cname) TargetRequestedByDefault
          target = AvailableTarget (packageId ipkg) cname status False
          fake   = False
       in [(packageId ipkg, cname, fake, target)]
  
  availableSourceTargets :: ElaboratedConfiguredPackage
                         -> [(PackageId, ComponentName, Bool,
                              AvailableTarget (UnitId, ComponentName))]
  availableSourceTargets elab =
      -- We have a somewhat awkward problem here. We need to know /all/ the
      -- components from /all/ the packages because these are the things that
      -- users could refer to. Unfortunately, at this stage the elaborated install
      -- plan does /not/ contain all components: some components have already
      -- been deleted because they cannot possibly be built. This is the case
      -- for components that are marked @buildable: False@ in their .cabal files.
      -- (It's not unreasonable that the unbuildable components have been pruned
      -- as the plan invariant is considerably simpler if all nodes can be built)
      --
      -- We can recover the missing components but it's not exactly elegant. For
      -- a graph node corresponding to a component we still have the information
      -- about the package that it came from, and this includes the names of
      -- /all/ the other components in the package. So in principle this lets us
      -- find the names of all components, plus full details of the buildable
      -- components.
      --
      -- Consider for example a package with 3 exe components: foo, bar and baz
      -- where foo and bar are buildable, but baz is not. So the plan contains
      -- nodes for the components foo and bar. Now we look at each of these two
      -- nodes and look at the package they come from and the names of the
      -- components in this package. This will give us the names foo, bar and
      -- baz, twice (once for each of the two buildable components foo and bar).
      --
      -- We refer to these reconstructed missing components as fake targets.
      -- It is an invariant that they are not available to be built.
      --
      -- To produce the final set of targets we put the fake targets in a finite
      -- map (thus eliminating the duplicates) and then we overlay that map with
      -- the normal buildable targets. (This is done above in 'availableTargets'.)
      --
      [ (packageId elab, cname, fake, target)
      | component <- pkgComponents (elabPkgDescription elab)
      , let cname  = componentName component
            status = componentAvailableTargetStatus component
            target = AvailableTarget {
                       availableTargetPackageId      = packageId elab,
                       availableTargetComponentName  = cname,
                       availableTargetStatus         = status,
                       availableTargetLocalToProject = elabLocalToProject elab
                     }
            fake   = isFakeTarget cname
  
      -- TODO: The goal of this test is to exclude "instantiated"
      -- packages as available targets. This means that you can't
      -- ask for a particular instantiated component to be built;
      -- it will only get built by a dependency.  Perhaps the
      -- correct way to implement this is to run selection
      -- prior to instantiating packages.  If you refactor
      -- this, then you can delete this test.
      , elabIsCanonical elab
  
        -- Filter out some bogus parts of the cross product that are never needed
      , case status of
          TargetBuildable{} | fake -> False
          _                        -> True
      ]
    where
      isFakeTarget cname =
        case elabPkgOrComp elab of
          ElabPackage _               -> False
          ElabComponent elabComponent -> compComponentName elabComponent
                                         /= Just cname
  
      componentAvailableTargetStatus
        :: Component -> AvailableTargetStatus (UnitId, ComponentName)
      componentAvailableTargetStatus component =
          case componentOptionalStanza (componentName component) of
            -- it is not an optional stanza, so a library, exe or foreign lib
            Nothing
              | not buildable  -> TargetNotBuildable
              | otherwise      -> TargetBuildable (elabUnitId elab, cname)
                                                  TargetRequestedByDefault
  
            -- it is not an optional stanza, so a testsuite or benchmark
            Just stanza ->
              case (Map.lookup stanza (elabStanzasRequested elab),
                    Set.member stanza (elabStanzasAvailable elab)) of
                _ | not withinPlan -> TargetNotLocal
                (Just False,   _)  -> TargetDisabledByUser
                (Nothing,  False)  -> TargetDisabledBySolver
                _ | not buildable  -> TargetNotBuildable
                (Just True, True)  -> TargetBuildable (elabUnitId elab, cname)
                                                      TargetRequestedByDefault
                (Nothing,   True)  -> TargetBuildable (elabUnitId elab, cname)
                                                      TargetNotRequestedByDefault
                (Just True, False) ->
                  error "componentAvailableTargetStatus: impossible"
        where
          cname      = componentName component
          buildable  = PD.buildable (componentBuildInfo component)
          withinPlan = elabLocalToProject elab
                    || case elabPkgOrComp elab of
                         ElabComponent elabComponent ->
                           compComponentName elabComponent == Just cname
                         ElabPackage _ ->
                           case componentName component of
                             CLibName   -> True
                             CExeName _ -> True
                             --TODO: what about sub-libs and foreign libs?
                             _          -> False
  
  -- | Merge component targets that overlap each other. Specially when we have
  -- multiple targets for the same component and one of them refers to the whole
  -- component (rather than a module or file within) then all the other targets
  -- for that component are subsumed.
  --
  -- We also allow for information associated with each component target, and
  -- whenever we targets subsume each other we aggregate their associated info.
  --
  nubComponentTargets :: [(ComponentTarget, a)] -> [(ComponentTarget, [a])]
  nubComponentTargets =
      concatMap (wholeComponentOverrides . map snd)
    . groupBy ((==)    `on` fst)
    . sortBy  (compare `on` fst)
    . map (\t@((ComponentTarget cname _, _)) -> (cname, t))
    . map compatSubComponentTargets
    where
      -- If we're building the whole component then that the only target all we
      -- need, otherwise we can have several targets within the component.
      wholeComponentOverrides :: [(ComponentTarget,  a )]
                              -> [(ComponentTarget, [a])]
      wholeComponentOverrides ts =
        case [ t | (t@(ComponentTarget _ WholeComponent), _) <- ts ] of
          (t:_) -> [ (t, map snd ts) ]
          []    -> [ (t,[x]) | (t,x) <- ts ]
  
      -- Not all Cabal Setup.hs versions support sub-component targets, so switch
      -- them over to the whole component
      compatSubComponentTargets :: (ComponentTarget, a) -> (ComponentTarget, a)
      compatSubComponentTargets target@(ComponentTarget cname _subtarget, x)
        | not setupHsSupportsSubComponentTargets
                    = (ComponentTarget cname WholeComponent, x)
        | otherwise = target
  
      -- Actually the reality is that no current version of Cabal's Setup.hs
      -- build command actually support building specific files or modules.
      setupHsSupportsSubComponentTargets = False
      -- TODO: when that changes, adjust this test, e.g.
      -- | pkgSetupScriptCliVersion >= Version [x,y] []
  
  pkgHasEphemeralBuildTargets :: ElaboratedConfiguredPackage -> Bool
  pkgHasEphemeralBuildTargets elab =
      isJust (elabReplTarget elab)
   || (not . null) (elabTestTargets elab)
   || (not . null) (elabBenchTargets elab)
   || (not . null) [ () | ComponentTarget _ subtarget <- elabBuildTargets elab
                        , subtarget /= WholeComponent ]
  
  -- | The components that we'll build all of, meaning that after they're built
  -- we can skip building them again (unlike with building just some modules or
  -- other files within a component).
  --
  elabBuildTargetWholeComponents :: ElaboratedConfiguredPackage
                                -> Set ComponentName
  elabBuildTargetWholeComponents elab =
      Set.fromList
        [ cname | ComponentTarget cname WholeComponent <- elabBuildTargets elab ]
  
  
  
  ------------------------------------------------------------------------------
  -- * Install plan pruning
  ------------------------------------------------------------------------------
  
  -- | How 'pruneInstallPlanToTargets' should interpret the per-package
  -- 'ComponentTarget's: as build, repl or haddock targets.
  --
  data TargetAction = TargetActionBuild
                    | TargetActionRepl
                    | TargetActionTest
                    | TargetActionBench
                    | TargetActionHaddock
  
  -- | Given a set of per-package\/per-component targets, take the subset of the
  -- install plan needed to build those targets. Also, update the package config
  -- to specify which optional stanzas to enable, and which targets within each
  -- package to build.
  --
  -- NB: Pruning happens after improvement, which is important because we
  -- will prune differently depending on what is already installed (to
  -- implement "sticky" test suite enabling behavior).
  --
  pruneInstallPlanToTargets :: TargetAction
                            -> Map UnitId [ComponentTarget]
                            -> ElaboratedInstallPlan -> ElaboratedInstallPlan
  pruneInstallPlanToTargets targetActionType perPkgTargetsMap elaboratedPlan =
      InstallPlan.new (InstallPlan.planIndepGoals elaboratedPlan)
    . Graph.fromDistinctList
      -- We have to do the pruning in two passes
    . pruneInstallPlanPass2
    . pruneInstallPlanPass1
      -- Set the targets that will be the roots for pruning
    . setRootTargets targetActionType perPkgTargetsMap
    . InstallPlan.toList
    $ elaboratedPlan
  
  -- | This is a temporary data type, where we temporarily
  -- override the graph dependencies of an 'ElaboratedPackage',
  -- so we can take a closure over them.  We'll throw out the
  -- overriden dependencies when we're done so it's strictly temporary.
  --
  -- For 'ElaboratedComponent', this the cached unit IDs always
  -- coincide with the real thing.
  data PrunedPackage = PrunedPackage ElaboratedConfiguredPackage [UnitId]
  
  instance Package PrunedPackage where
      packageId (PrunedPackage elab _) = packageId elab
  
  instance HasUnitId PrunedPackage where
      installedUnitId = nodeKey
  
  instance IsNode PrunedPackage where
      type Key PrunedPackage = UnitId
      nodeKey (PrunedPackage elab _)  = nodeKey elab
      nodeNeighbors (PrunedPackage _ deps) = deps
  
  fromPrunedPackage :: PrunedPackage -> ElaboratedConfiguredPackage
  fromPrunedPackage (PrunedPackage elab _) = elab
  
  -- | Set the build targets based on the user targets (but not rev deps yet).
  -- This is required before we can prune anything.
  --
  setRootTargets :: TargetAction
                 -> Map UnitId [ComponentTarget]
                 -> [ElaboratedPlanPackage]
                 -> [ElaboratedPlanPackage]
  setRootTargets targetAction perPkgTargetsMap =
      assert (not (Map.null perPkgTargetsMap)) $
      assert (all (not . null) (Map.elems perPkgTargetsMap)) $
  
      map (mapConfiguredPackage setElabBuildTargets)
    where
      -- Set the targets we'll build for this package/component. This is just
      -- based on the root targets from the user, not targets implied by reverse
      -- dependencies. Those comes in the second pass once we know the rev deps.
      --
      setElabBuildTargets elab =
        case (Map.lookup (installedUnitId elab) perPkgTargetsMap,
              targetAction) of
          (Nothing, _)                      -> elab
          (Just tgts,  TargetActionBuild)   -> elab { elabBuildTargets  = tgts     }
          (Just tgts,  TargetActionTest)    -> elab { elabTestTargets   = tgts     }
          (Just tgts,  TargetActionBench)   -> elab { elabBenchTargets  = tgts     }
          (Just [tgt], TargetActionRepl)    -> elab { elabReplTarget    = Just tgt }
          (Just _,     TargetActionHaddock) -> elab { elabBuildHaddocks = True     }
          (Just _,     TargetActionRepl)    ->
            error "pruneInstallPlanToTargets: multiple repl targets"
  
  -- | Assuming we have previously set the root build targets (i.e. the user
  -- targets but not rev deps yet), the first pruning pass does two things:
  --
  -- * A first go at determining which optional stanzas (testsuites, benchmarks)
  --   are needed. We have a second go in the next pass.
  -- * Take the dependency closure using pruned dependencies. We prune deps that
  --   are used only by unneeded optional stanzas. These pruned deps are only
  --   used for the dependency closure and are not persisted in this pass.
  --
  pruneInstallPlanPass1 :: [ElaboratedPlanPackage]
                        -> [ElaboratedPlanPackage]
  pruneInstallPlanPass1 pkgs =
      map (mapConfiguredPackage fromPrunedPackage)
          (fromMaybe [] $ Graph.closure graph roots)
    where
      pkgs' = map (mapConfiguredPackage prune) pkgs
      graph = Graph.fromDistinctList pkgs'
      roots = mapMaybe find_root pkgs'
  
      prune elab = PrunedPackage elab' (pruneOptionalDependencies elab')
        where elab' = addOptionalStanzas elab
  
      find_root (InstallPlan.Configured (PrunedPackage elab _)) =
          if not (null (elabBuildTargets elab)
                      && null (elabTestTargets elab)
                      && null (elabBenchTargets elab)
                      && isNothing (elabReplTarget elab)
                      && not (elabBuildHaddocks elab))
              then Just (installedUnitId elab)
              else Nothing
      find_root _ = Nothing
  
      -- Note [Sticky enabled testsuites]
      -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      -- The testsuite and benchmark targets are somewhat special in that we need
      -- to configure the packages with them enabled, and we need to do that even
      -- if we only want to build one of several testsuites.
      --
      -- There are two cases in which we will enable the testsuites (or
      -- benchmarks): if one of the targets is a testsuite, or if all of the
      -- testsuite dependencies are already cached in the store. The rationale
      -- for the latter is to minimise how often we have to reconfigure due to
      -- the particular targets we choose to build. Otherwise choosing to build
      -- a testsuite target, and then later choosing to build an exe target
      -- would involve unnecessarily reconfiguring the package with testsuites
      -- disabled. Technically this introduces a little bit of stateful
      -- behaviour to make this "sticky", but it should be benign.
  
      -- Decide whether or not to enable testsuites and benchmarks.
      -- See [Sticky enabled testsuites]
      addOptionalStanzas :: ElaboratedConfiguredPackage -> ElaboratedConfiguredPackage
      addOptionalStanzas elab@ElaboratedConfiguredPackage{ elabPkgOrComp = ElabPackage pkg } =
          elab {
              elabPkgOrComp = ElabPackage (pkg { pkgStanzasEnabled = stanzas })
          }
        where
          stanzas :: Set OptionalStanza
                 -- By default, we enabled all stanzas requested by the user,
                 -- as per elabStanzasRequested, done in
                 -- 'elaborateSolverToPackage'
          stanzas = pkgStanzasEnabled pkg
                 -- optionalStanzasRequiredByTargets has to be done at
                 -- prune-time because it depends on 'elabTestTargets'
                 -- et al, which is done by 'setRootTargets' at the
                 -- beginning of pruning.
                 <> optionalStanzasRequiredByTargets elab
                 -- optionalStanzasWithDepsAvailable has to be done at
                 -- prune-time because it depends on what packages are
                 -- installed, which is not known until after improvement
                 -- (pruning is done after improvement)
                 <> optionalStanzasWithDepsAvailable availablePkgs elab pkg
      addOptionalStanzas elab = elab
  
      -- Calculate package dependencies but cut out those needed only by
      -- optional stanzas that we've determined we will not enable.
      -- These pruned deps are not persisted in this pass since they're based on
      -- the optional stanzas and we'll make further tweaks to the optional
      -- stanzas in the next pass.
      --
      pruneOptionalDependencies :: ElaboratedConfiguredPackage -> [UnitId]
      pruneOptionalDependencies elab@ElaboratedConfiguredPackage{ elabPkgOrComp = ElabComponent _ }
          = InstallPlan.depends elab -- no pruning
      pruneOptionalDependencies ElaboratedConfiguredPackage{ elabPkgOrComp = ElabPackage pkg }
          = (CD.flatDeps . CD.filterDeps keepNeeded) (pkgOrderDependencies pkg)
        where
          keepNeeded (CD.ComponentTest  _) _ = TestStanzas  `Set.member` stanzas
          keepNeeded (CD.ComponentBench _) _ = BenchStanzas `Set.member` stanzas
          keepNeeded _                     _ = True
          stanzas = pkgStanzasEnabled pkg
  
      optionalStanzasRequiredByTargets :: ElaboratedConfiguredPackage
                                       -> Set OptionalStanza
      optionalStanzasRequiredByTargets pkg =
        Set.fromList
          [ stanza
          | ComponentTarget cname _ <- elabBuildTargets pkg
                                    ++ elabTestTargets pkg
                                    ++ elabBenchTargets pkg
                                    ++ maybeToList (elabReplTarget pkg)
          , stanza <- maybeToList (componentOptionalStanza cname)
          ]
  
      availablePkgs =
        Set.fromList
          [ installedUnitId pkg
          | InstallPlan.PreExisting pkg <- pkgs ]
  
  -- | Given a set of already installed packages @availablePkgs@,
  -- determine the set of available optional stanzas from @pkg@
  -- which have all of their dependencies already installed.  This is used
  -- to implement "sticky" testsuites, where once we have installed
  -- all of the deps needed for the test suite, we go ahead and
  -- enable it always.
  optionalStanzasWithDepsAvailable :: Set UnitId
                                   -> ElaboratedConfiguredPackage
                                   -> ElaboratedPackage
                                   -> Set OptionalStanza
  optionalStanzasWithDepsAvailable availablePkgs elab pkg =
      Set.fromList
        [ stanza
        | stanza <- Set.toList (elabStanzasAvailable elab)
        , let deps :: [UnitId]
              deps = CD.select (optionalStanzaDeps stanza)
                               -- TODO: probably need to select other
                               -- dep types too eventually
                               (pkgOrderDependencies pkg)
        , all (`Set.member` availablePkgs) deps
        ]
    where
      optionalStanzaDeps TestStanzas  (CD.ComponentTest  _) = True
      optionalStanzaDeps BenchStanzas (CD.ComponentBench _) = True
      optionalStanzaDeps _            _                     = False
  
  
  -- The second pass does three things:
  --
  -- * A second go at deciding which optional stanzas to enable.
  -- * Prune the dependencies based on the final choice of optional stanzas.
  -- * Extend the targets within each package to build, now we know the reverse
  --   dependencies, ie we know which libs are needed as deps by other packages.
  --
  -- Achieving sticky behaviour with enabling\/disabling optional stanzas is
  -- tricky. The first approximation was handled by the first pass above, but
  -- it's not quite enough. That pass will enable stanzas if all of the deps
  -- of the optional stanza are already installed /in the store/. That's important
  -- but it does not account for dependencies that get built inplace as part of
  -- the project. We cannot take those inplace build deps into account in the
  -- pruning pass however because we don't yet know which ones we're going to
  -- build. Once we do know, we can have another go and enable stanzas that have
  -- all their deps available. Now we can consider all packages in the pruned
  -- plan to be available, including ones we already decided to build from
  -- source.
  --
  -- Deciding which targets to build depends on knowing which packages have
  -- reverse dependencies (ie are needed). This requires the result of first
  -- pass, which is another reason we have to split it into two passes.
  --
  -- Note that just because we might enable testsuites or benchmarks (in the
  -- first or second pass) doesn't mean that we build all (or even any) of them.
  -- That depends on which targets we picked in the first pass.
  --
  pruneInstallPlanPass2 :: [ElaboratedPlanPackage]
                        -> [ElaboratedPlanPackage]
  pruneInstallPlanPass2 pkgs =
      map (mapConfiguredPackage setStanzasDepsAndTargets) pkgs
    where
      setStanzasDepsAndTargets elab =
          elab {
            elabBuildTargets = ordNub
                             $ elabBuildTargets elab
                            ++ libTargetsRequiredForRevDeps
                            ++ exeTargetsRequiredForRevDeps,
            elabPkgOrComp =
              case elabPkgOrComp elab of
                ElabPackage pkg ->
                  let stanzas = pkgStanzasEnabled pkg
                             <> optionalStanzasWithDepsAvailable availablePkgs elab pkg
                      keepNeeded (CD.ComponentTest  _) _ = TestStanzas  `Set.member` stanzas
                      keepNeeded (CD.ComponentBench _) _ = BenchStanzas `Set.member` stanzas
                      keepNeeded _                     _ = True
                  in ElabPackage $ pkg {
                    pkgStanzasEnabled = stanzas,
                    pkgLibDependencies   = CD.filterDeps keepNeeded (pkgLibDependencies pkg),
                    pkgExeDependencies   = CD.filterDeps keepNeeded (pkgExeDependencies pkg),
                    pkgExeDependencyPaths = CD.filterDeps keepNeeded (pkgExeDependencyPaths pkg)
                  }
                r@(ElabComponent _) -> r
          }
        where
          libTargetsRequiredForRevDeps =
            [ ComponentTarget Cabal.defaultLibName WholeComponent
            | installedUnitId elab `Set.member` hasReverseLibDeps
            ]
          exeTargetsRequiredForRevDeps =
            -- TODO: allow requesting executable with different name
            -- than package name
            [ ComponentTarget (Cabal.CExeName
                               $ packageNameToUnqualComponentName
                               $ packageName $ elabPkgSourceId elab)
                              WholeComponent
            | installedUnitId elab `Set.member` hasReverseExeDeps
            ]
  
  
      availablePkgs :: Set UnitId
      availablePkgs = Set.fromList (map installedUnitId pkgs)
  
      hasReverseLibDeps :: Set UnitId
      hasReverseLibDeps =
        Set.fromList [ depid
                     | InstallPlan.Configured pkg <- pkgs
                     , depid <- elabOrderLibDependencies pkg ]
  
      hasReverseExeDeps :: Set UnitId
      hasReverseExeDeps =
        Set.fromList [ depid
                     | InstallPlan.Configured pkg <- pkgs
                     , depid <- elabOrderExeDependencies pkg ]
  
  mapConfiguredPackage :: (srcpkg -> srcpkg')
                       -> InstallPlan.GenericPlanPackage ipkg srcpkg
                       -> InstallPlan.GenericPlanPackage ipkg srcpkg'
  mapConfiguredPackage f (InstallPlan.Configured pkg) =
    InstallPlan.Configured (f pkg)
  mapConfiguredPackage f (InstallPlan.Installed pkg) =
    InstallPlan.Installed (f pkg)
  mapConfiguredPackage _ (InstallPlan.PreExisting pkg) =
    InstallPlan.PreExisting pkg
  
  componentOptionalStanza :: Cabal.ComponentName -> Maybe OptionalStanza
  componentOptionalStanza (Cabal.CTestName  _) = Just TestStanzas
  componentOptionalStanza (Cabal.CBenchName _) = Just BenchStanzas
  componentOptionalStanza _                    = Nothing
  
  ------------------------------------
  -- Support for --only-dependencies
  --
  
  -- | Try to remove the given targets from the install plan.
  --
  -- This is not always possible.
  --
  pruneInstallPlanToDependencies :: Set UnitId
                                 -> ElaboratedInstallPlan
                                 -> Either CannotPruneDependencies
                                           ElaboratedInstallPlan
  pruneInstallPlanToDependencies pkgTargets installPlan =
      assert (all (isJust . InstallPlan.lookup installPlan)
                  (Set.toList pkgTargets)) $
  
      fmap (InstallPlan.new (InstallPlan.planIndepGoals installPlan))
    . checkBrokenDeps
    . Graph.fromDistinctList
    . filter (\pkg -> installedUnitId pkg `Set.notMember` pkgTargets)
    . InstallPlan.toList
    $ installPlan
      where
        -- Our strategy is to remove the packages we don't want and then check
        -- if the remaining graph is broken or not, ie any packages with dangling
        -- dependencies. If there are then we cannot prune the given targets.
        checkBrokenDeps :: Graph.Graph ElaboratedPlanPackage
                        -> Either CannotPruneDependencies
                                  (Graph.Graph ElaboratedPlanPackage)
        checkBrokenDeps graph =
          case Graph.broken graph of
            []             -> Right graph
            brokenPackages ->
              Left $ CannotPruneDependencies
               [ (pkg, missingDeps)
               | (pkg, missingDepIds) <- brokenPackages
               , let missingDeps = mapMaybe lookupDep missingDepIds
               ]
              where
                -- lookup in the original unpruned graph
                lookupDep = InstallPlan.lookup installPlan
  
  -- | It is not always possible to prune to only the dependencies of a set of
  -- targets. It may be the case that removing a package leaves something else
  -- that still needed the pruned package.
  --
  -- This lists all the packages that would be broken, and their dependencies
  -- that would be missing if we did prune.
  --
  newtype CannotPruneDependencies =
          CannotPruneDependencies [(ElaboratedPlanPackage,
                                    [ElaboratedPlanPackage])]
    deriving (Show)
  
  
  ---------------------------
  -- Setup.hs script policy
  --
  
  -- Handling for Setup.hs scripts is a bit tricky, part of it lives in the
  -- solver phase, and part in the elaboration phase. We keep the helper
  -- functions for both phases together here so at least you can see all of it
  -- in one place.
  --
  -- There are four major cases for Setup.hs handling:
  --
  --  1. @build-type@ Custom with a @custom-setup@ section
  --  2. @build-type@ Custom without a @custom-setup@ section
  --  3. @build-type@ not Custom with @cabal-version >  $our-cabal-version@
  --  4. @build-type@ not Custom with @cabal-version <= $our-cabal-version@
  --
  -- It's also worth noting that packages specifying @cabal-version: >= 1.23@
  -- or later that have @build-type@ Custom will always have a @custom-setup@
  -- section. Therefore in case 2, the specified @cabal-version@ will always be
  -- less than 1.23.
  --
  -- In cases 1 and 2 we obviously have to build an external Setup.hs script,
  -- while in case 4 we can use the internal library API. In case 3 we also have
  -- to build an external Setup.hs script because the package needs a later
  -- Cabal lib version than we can support internally.
  --
  -- data SetupScriptStyle = ...  -- see ProjectPlanning.Types
  
  -- | Work out the 'SetupScriptStyle' given the package description.
  --
  packageSetupScriptStyle :: PD.PackageDescription -> SetupScriptStyle
  packageSetupScriptStyle pkg
    | buildType == PD.Custom
    , Just setupbi <- PD.setupBuildInfo pkg -- does have a custom-setup stanza
    , not (PD.defaultSetupDepends setupbi)  -- but not one we added internally
    = SetupCustomExplicitDeps
  
    | buildType == PD.Custom
    , Just setupbi <- PD.setupBuildInfo pkg -- we get this case post-solver as
    , PD.defaultSetupDepends setupbi        -- the solver fills in the deps
    = SetupCustomImplicitDeps
  
    | buildType == PD.Custom
    , Nothing <- PD.setupBuildInfo pkg      -- we get this case pre-solver
    = SetupCustomImplicitDeps
  
    | PD.specVersion pkg > cabalVersion -- one etlas is built against
    = SetupNonCustomExternalLib
  
    | otherwise
    = SetupNonCustomInternalLib
    where
      buildType = fromMaybe PD.Custom (PD.buildType pkg)
  
  
  -- | Part of our Setup.hs handling policy is implemented by getting the solver
  -- to work out setup dependencies for packages. The solver already handles
  -- packages that explicitly specify setup dependencies, but we can also tell
  -- the solver to treat other packages as if they had setup dependencies.
  -- That's what this function does, it gets called by the solver for all
  -- packages that don't already have setup dependencies.
  --
  -- The dependencies we want to add is different for each 'SetupScriptStyle'.
  --
  -- Note that adding default deps means these deps are actually /added/ to the
  -- packages that we get out of the solver in the 'SolverInstallPlan'. Making
  -- implicit setup deps explicit is a problem in the post-solver stages because
  -- we still need to distinguish the case of explicit and implict setup deps.
  -- See 'rememberImplicitSetupDeps'.
  --
  -- Note in addition to adding default setup deps, we also use
  -- 'addSetupCabalMinVersionConstraint' (in 'planPackages') to require
  -- @Cabal >= 1.20@ for Setup scripts.
  --
  defaultSetupDeps :: Compiler -> Platform
                   -> PD.PackageDescription
                   -> Maybe [Dependency]
  defaultSetupDeps compiler platform pkg =
      case packageSetupScriptStyle pkg of
  
        -- For packages with build type custom that do not specify explicit
        -- setup dependencies, we add a dependency on Cabal and a number
        -- of other packages.
        SetupCustomImplicitDeps ->
          Just $
          [ Dependency depPkgname anyVersion
          | depPkgname <- legacyCustomSetupPkgs compiler platform ] ++
          [ Dependency cabalPkgname cabalConstraint
          | packageName pkg /= cabalPkgname ]
          where
            -- The Cabal dep is slightly special:
            -- * We omit the dep for the Cabal lib itself, since it bootstraps.
            -- * We constrain it to be < 1.25
            --
            -- Note: we also add a global constraint to require Cabal >= 1.20
            -- for Setup scripts (see use addSetupCabalMinVersionConstraint).
            --
            cabalConstraint   = orLaterVersion (PD.specVersion pkg)
                                  `intersectVersionRanges`
                                earlierVersion cabalCompatMaxVer
            -- The idea here is that at some point we will make significant
            -- breaking changes to the Cabal API that Setup.hs scripts use.
            -- So for old custom Setup scripts that do not specify explicit
            -- constraints, we constrain them to use a compatible Cabal version.
            cabalCompatMaxVer = mkVersion [1,25]
  
        -- For other build types (like Simple) if we still need to compile an
        -- external Setup.hs, it'll be one of the simple ones that only depends
        -- on Cabal and base.
        SetupNonCustomExternalLib ->
          Just [ Dependency cabalPkgname cabalConstraint
               , Dependency basePkgname  anyVersion ]
          where
            cabalConstraint = orLaterVersion (PD.specVersion pkg)
  
        -- The internal setup wrapper method has no deps at all.
        SetupNonCustomInternalLib -> Just []
  
        -- This case gets ruled out by the caller, planPackages, see the note
        -- above in the SetupCustomImplicitDeps case.
        SetupCustomExplicitDeps ->
          error $ "defaultSetupDeps: called for a package with explicit "
               ++ "setup deps: " ++ display (packageId pkg)
  
  
  -- | Work out which version of the Cabal spec we will be using to talk to the
  -- Setup.hs interface for this package.
  --
  -- This depends somewhat on the 'SetupScriptStyle' but most cases are a result
  -- of what the solver picked for us, based on the explicit setup deps or the
  -- ones added implicitly by 'defaultSetupDeps'.
  --
  packageSetupScriptSpecVersion :: Package pkg
                                => SetupScriptStyle
                                -> PD.PackageDescription
                                -> ComponentDeps [pkg]
                                -> Version
  
  -- We're going to be using the internal Cabal library, so the spec version of
  -- that is simply the version of the Cabal library that etlas has been
  -- built with.
  packageSetupScriptSpecVersion SetupNonCustomInternalLib _ _ =
      cabalVersion
  
  -- If we happen to be building the Cabal lib itself then because that
  -- bootstraps itself then we use the version of the lib we're building.
  packageSetupScriptSpecVersion SetupCustomImplicitDeps pkg _
    | packageName pkg == cabalPkgname
    = packageVersion pkg
  
  -- In all other cases we have a look at what version of the Cabal lib the
  -- solver picked. Or if it didn't depend on Cabal at all (which is very rare)
  -- then we look at the .cabal file to see what spec version it declares.
  packageSetupScriptSpecVersion _ pkg deps =
      case find ((cabalPkgname ==) . packageName) (CD.setupDeps deps) of
        Just dep -> packageVersion dep
        Nothing  -> PD.specVersion pkg
  
  
  cabalPkgname, basePkgname :: PackageName
  cabalPkgname = mkPackageName "etlas-cabal"
  basePkgname  = mkPackageName "base"
  
  
  legacyCustomSetupPkgs :: Compiler -> Platform -> [PackageName]
  legacyCustomSetupPkgs compiler (Platform _ os) =
      map mkPackageName $
          [ "array", "base", "binary", "bytestring", "containers"
          , "deepseq", "directory", "filepath", "old-time", "pretty"
          , "process", "time", "transformers" ]
       ++ [ "Win32" | os == Windows ]
       ++ [ "unix"  | os /= Windows ]
       ++ [ "ghc-prim"         | isGHC ]
       ++ [ "eta-meta"         | isGHC ]
       ++ [ "template-haskell" | isGHC ]
    where
      isGHC = compilerCompatFlavor GHC compiler
  
  -- The other aspects of our Setup.hs policy lives here where we decide on
  -- the 'SetupScriptOptions'.
  --
  -- Our current policy for the 'SetupCustomImplicitDeps' case is that we
  -- try to make the implicit deps cover everything, and we don't allow the
  -- compiler to pick up other deps. This may or may not be sustainable, and
  -- we might have to allow the deps to be non-exclusive, but that itself would
  -- be tricky since we would have to allow the Setup access to all the packages
  -- in the store and local dbs.
  
  setupHsScriptOptions :: ElaboratedReadyPackage
                       -> ElaboratedSharedConfig
                       -> FilePath
                       -> FilePath
                       -> Bool
                       -> Lock
                       -> SetupScriptOptions
  -- TODO: Fix this so custom is a separate component.  Custom can ALWAYS
  -- be a separate component!!!
  setupHsScriptOptions (ReadyPackage elab@ElaboratedConfiguredPackage{..})
                       ElaboratedSharedConfig{..} srcdir builddir
                       isParallelBuild cacheLock =
      SetupScriptOptions {
        useCabalVersion          = thisVersion elabSetupScriptCliVersion,
        useCabalSpecVersion      = Just elabSetupScriptCliVersion,
        useCompiler              = Just pkgConfigCompiler,
        usePlatform              = Just pkgConfigPlatform,
        usePackageDB             = elabSetupPackageDBStack,
        usePackageIndex          = Nothing,
        useDependencies          = [ (uid, srcid)
                                   | ConfiguredId srcid (Just CLibName) uid
                                   <- elabSetupDependencies elab ],
        useDependenciesExclusive = True,
        useVersionMacros         = elabSetupScriptStyle == SetupCustomExplicitDeps,
        useProgramDb             = pkgConfigCompilerProgs,
        useDistPref              = builddir,
        useLoggingHandle         = Nothing, -- this gets set later
        useWorkingDir            = Just srcdir,
        useExtraPathEnv          = elabExeDependencyPaths elab,
        useWin32CleanHack        = False,   --TODO: [required eventually]
        forceExternalSetupMethod = isParallelBuild,
        setupCacheLock           = Just cacheLock,
        isInteractive            = False
      }
  
  
  -- | To be used for the input for elaborateInstallPlan.
  --
  -- TODO: [code cleanup] make InstallDirs.defaultInstallDirs pure.
  --
  userInstallDirTemplates :: Compiler
                          -> IO InstallDirs.InstallDirTemplates
  userInstallDirTemplates compiler = do
      InstallDirs.defaultInstallDirs
                    (compilerFlavor compiler)
                    True  -- user install
                    False -- unused
  
  storePackageInstallDirs :: StoreDirLayout
                          -> CompilerId
                          -> InstalledPackageId
                          -> InstallDirs.InstallDirs FilePath
  storePackageInstallDirs StoreDirLayout{storePackageDirectory}
                          compid ipkgid =
      InstallDirs.InstallDirs {..}
    where
      prefix       = storePackageDirectory compid (newSimpleUnitId ipkgid)
      bindir       = prefix </> "bin"
      libdir       = prefix </> "lib"
      libsubdir    = ""
      dynlibdir    = libdir
      flibdir      = libdir
      libexecdir   = prefix </> "libexec"
      includedir   = libdir </> "include"
      datadir      = prefix </> "share"
      datasubdir   = ""
      docdir       = datadir </> "doc"
      mandir       = datadir </> "man"
      htmldir      = docdir  </> "html"
      haddockdir   = htmldir
      sysconfdir   = prefix </> "etc"
  
  
  --TODO: [code cleanup] perhaps reorder this code
  -- based on the ElaboratedInstallPlan + ElaboratedSharedConfig,
  -- make the various Setup.hs {configure,build,copy} flags
  
  
  setupHsConfigureFlags :: ElaboratedReadyPackage
                        -> ElaboratedSharedConfig
                        -> Verbosity
                        -> FilePath
                        -> Cabal.ConfigFlags
  setupHsConfigureFlags (ReadyPackage elab@ElaboratedConfiguredPackage{..})
                        sharedConfig@ElaboratedSharedConfig{..}
                        verbosity builddir =
      sanityCheckElaboratedConfiguredPackage sharedConfig elab
          (Cabal.ConfigFlags {..})
    where
      configArgs                = mempty -- unused, passed via args
      configDistPref            = toFlag builddir
      configCabalFilePath       = mempty
      configVerbosity           = toFlag verbosity
  
      configInstantiateWith     = Map.toList elabInstantiatedWith
  
      configDeterministic       = mempty -- doesn't matter, configIPID/configCID overridese
      configIPID                = case elabPkgOrComp of
                                    ElabPackage pkg -> toFlag (display (pkgInstalledId pkg))
                                    ElabComponent _ -> mempty
      configCID                 = case elabPkgOrComp of
                                    ElabPackage _ -> mempty
                                    ElabComponent _ -> toFlag elabComponentId
  
      configProgramPaths        = Map.toList elabProgramPaths
      configProgramArgs         = Map.toList elabProgramArgs
      configProgramPathExtra    = toNubList elabProgramPathExtra
      configHcFlavor            = toFlag (compilerFlavor pkgConfigCompiler)
      configHcPath              = mempty -- we use configProgramPaths instead
      configHcPkg               = mempty -- we use configProgramPaths instead
  
      configVanillaLib          = toFlag elabVanillaLib
      configSharedLib           = toFlag elabSharedLib
      configDynExe              = toFlag elabDynExe
      configGHCiLib             = toFlag elabGHCiLib
      configProfExe             = mempty
      configProfLib             = toFlag elabProfLib
      configProf                = toFlag elabProfExe
      configVerifyMode          = toFlag elabVerifyMode
  
      -- configProfDetail is for exe+lib, but overridden by configProfLibDetail
      -- so we specify both so we can specify independently
      configProfDetail          = toFlag elabProfExeDetail
      configProfLibDetail       = toFlag elabProfLibDetail
  
      configCoverage            = toFlag elabCoverage
      configLibCoverage         = mempty
  
      configOptimization        = toFlag elabOptimization
      configSplitObjs           = toFlag elabSplitObjs
      configStripExes           = toFlag elabStripExes
      configStripLibs           = toFlag elabStripLibs
      configDebugInfo           = toFlag elabDebugInfo
      configAllowOlder          = mempty -- we use configExactConfiguration True
      configAllowNewer          = mempty -- we use configExactConfiguration True
  
      configConfigurationsFlags = elabFlagAssignment
      configConfigureArgs       = elabConfigureScriptArgs
      configExtraLibDirs        = elabExtraLibDirs
      configExtraFrameworkDirs  = elabExtraFrameworkDirs
      configExtraIncludeDirs    = elabExtraIncludeDirs
      configProgPrefix          = maybe mempty toFlag elabProgPrefix
      configProgSuffix          = maybe mempty toFlag elabProgSuffix
  
      configInstallDirs         = fmap (toFlag . InstallDirs.toPathTemplate)
                                       elabInstallDirs
  
      -- we only use configDependencies, unless we're talking to an old Cabal
      -- in which case we use configConstraints
      -- NB: This does NOT use InstallPlan.depends, which includes executable
      -- dependencies which should NOT be fed in here (also you don't have
      -- enough info anyway)
      configDependencies        = [ (case mb_cn of
                                      -- Special case for internal libraries
                                      Just (CSubLibName uqn)
                                          | packageId elab == srcid
                                          -> mkPackageName (unUnqualComponentName uqn)
                                      _ -> packageName srcid,
                                     cid)
                                  | ConfiguredId srcid mb_cn cid <- elabLibDependencies elab ]
      configConstraints         =
          case elabPkgOrComp of
              ElabPackage _ ->
                  [ thisPackageVersion srcid
                  | ConfiguredId srcid _ _uid <- elabLibDependencies elab ]
              ElabComponent _ -> []
  
  
      -- explicitly clear, then our package db stack
      -- TODO: [required eventually] have to do this differently for older Cabal versions
      configPackageDBs          = Nothing : map Just elabBuildPackageDBStack
  
      configTests               = case elabPkgOrComp of
                                      ElabPackage pkg -> toFlag (TestStanzas  `Set.member` pkgStanzasEnabled pkg)
                                      ElabComponent _ -> mempty
      configBenchmarks          = case elabPkgOrComp of
                                      ElabPackage pkg -> toFlag (BenchStanzas `Set.member` pkgStanzasEnabled pkg)
                                      ElabComponent _ -> mempty
  
      configExactConfiguration  = toFlag True
      configFlagError           = mempty --TODO: [research required] appears not to be implemented
      configRelocatable         = mempty --TODO: [research required] ???
      configScratchDir          = mempty -- never use
      configUserInstall         = mempty -- don't rely on defaults
      configPrograms_           = mempty -- never use, shouldn't exist
  
  
  setupHsConfigureArgs :: ElaboratedConfiguredPackage
                       -> [String]
  setupHsConfigureArgs (ElaboratedConfiguredPackage { elabPkgOrComp = ElabPackage _ }) = []
  setupHsConfigureArgs elab@(ElaboratedConfiguredPackage { elabPkgOrComp = ElabComponent comp }) =
      [showComponentTarget (packageId elab) (ComponentTarget cname WholeComponent)]
    where
      cname = fromMaybe (error "setupHsConfigureArgs: trying to configure setup")
                        (compComponentName comp)
  
  setupHsBuildFlags :: ElaboratedConfiguredPackage
                    -> ElaboratedSharedConfig
                    -> Verbosity
                    -> FilePath
                    -> Cabal.BuildFlags
  setupHsBuildFlags _ _ verbosity builddir =
      Cabal.BuildFlags {
        buildProgramPaths = mempty, --unused, set at configure time
        buildProgramArgs  = mempty, --unused, set at configure time
        buildVerbosity    = toFlag verbosity,
        buildDistPref     = toFlag builddir,
        buildNumJobs      = mempty, --TODO: [nice to have] sometimes want to use toFlag (Just numBuildJobs),
        buildArgs         = mempty  -- unused, passed via args not flags
      }
  
  
  setupHsBuildArgs :: ElaboratedConfiguredPackage -> [String]
  setupHsBuildArgs elab@(ElaboratedConfiguredPackage { elabPkgOrComp = ElabPackage _ })
      -- Fix for #3335, don't pass build arguments if it's not supported
      | elabSetupScriptCliVersion elab >= mkVersion [1,17]
      = map (showComponentTarget (packageId elab)) (elabBuildTargets elab)
      | otherwise
      = []
  setupHsBuildArgs (ElaboratedConfiguredPackage { elabPkgOrComp = ElabComponent _ })
      = []
  
  
  setupHsTestFlags :: ElaboratedConfiguredPackage
                   -> ElaboratedSharedConfig
                   -> Verbosity
                   -> FilePath
                   -> Cabal.TestFlags
  setupHsTestFlags _ _ verbosity builddir = Cabal.TestFlags
      { testDistPref    = toFlag builddir
      , testVerbosity   = toFlag verbosity
      , testMachineLog  = mempty
      , testHumanLog    = mempty
      , testShowDetails = toFlag Cabal.Always
      , testKeepTix     = mempty
      , testOptions     = mempty
      }
  
  setupHsTestArgs :: ElaboratedConfiguredPackage -> [String]
  -- TODO: Does the issue #3335 affects test as well
  setupHsTestArgs elab =
      mapMaybe (showTestComponentTarget (packageId elab)) (elabTestTargets elab)
  
  
  setupHsBenchFlags :: ElaboratedConfiguredPackage
                    -> ElaboratedSharedConfig
                    -> Verbosity
                    -> FilePath
                    -> Cabal.BenchmarkFlags
  setupHsBenchFlags _ _ verbosity builddir = Cabal.BenchmarkFlags
      { benchmarkDistPref  = toFlag builddir
      , benchmarkVerbosity = toFlag verbosity
      , benchmarkOptions   = mempty
      }
  
  setupHsBenchArgs :: ElaboratedConfiguredPackage -> [String]
  setupHsBenchArgs elab =
      mapMaybe (showBenchComponentTarget (packageId elab)) (elabBenchTargets elab)
  
  
  setupHsReplFlags :: ElaboratedConfiguredPackage
                   -> ElaboratedSharedConfig
                   -> Verbosity
                   -> FilePath
                   -> Cabal.ReplFlags
  setupHsReplFlags _ _ verbosity builddir =
      Cabal.ReplFlags {
        replProgramPaths = mempty, --unused, set at configure time
        replProgramArgs  = mempty, --unused, set at configure time
        replVerbosity    = toFlag verbosity,
        replDistPref     = toFlag builddir,
        replReload       = mempty  --only used as callback from repl
      }
  
  
  setupHsReplArgs :: ElaboratedConfiguredPackage -> [String]
  setupHsReplArgs elab =
      maybe [] (\t -> [showComponentTarget (packageId elab) t]) (elabReplTarget elab)
      --TODO: should be able to give multiple modules in one component
  
  
  setupHsCopyFlags :: ElaboratedConfiguredPackage
                   -> ElaboratedSharedConfig
                   -> Verbosity
                   -> FilePath
                   -> FilePath
                   -> Cabal.CopyFlags
  setupHsCopyFlags _ _ verbosity builddir destdir =
      Cabal.CopyFlags {
        copyArgs      = [], -- TODO: could use this to only copy what we enabled
        copyDest      = toFlag (InstallDirs.CopyTo destdir),
        copyDistPref  = toFlag builddir,
        copyVerbosity = toFlag verbosity
      }
  
  setupHsRegisterFlags :: ElaboratedConfiguredPackage
                       -> ElaboratedSharedConfig
                       -> Verbosity
                       -> FilePath
                       -> FilePath
                       -> Cabal.RegisterFlags
  setupHsRegisterFlags ElaboratedConfiguredPackage{..} _
                       verbosity builddir pkgConfFile =
      Cabal.RegisterFlags {
        regPackageDB   = mempty,  -- misfeature
        regGenScript   = mempty,  -- never use
        regGenPkgConf  = toFlag (Just pkgConfFile),
        regInPlace     = case elabBuildStyle of
                           BuildInplaceOnly -> toFlag True
                           _                -> toFlag False,
        regPrintId     = mempty,  -- never use
        regDistPref    = toFlag builddir,
        regArgs        = [],
        regVerbosity   = toFlag verbosity,
        regBinary      = mempty
      }
  
  setupHsHaddockFlags :: ElaboratedConfiguredPackage
                      -> ElaboratedSharedConfig
                      -> Verbosity
                      -> FilePath
                      -> Cabal.HaddockFlags
  -- TODO: reconsider whether or not Executables/TestSuites/...
  -- needed for component
  setupHsHaddockFlags (ElaboratedConfiguredPackage{..}) _ verbosity builddir =
      Cabal.HaddockFlags {
        haddockProgramPaths  = mempty, --unused, set at configure time
        haddockProgramArgs   = mempty, --unused, set at configure time
        haddockHoogle        = toFlag elabHaddockHoogle,
        haddockHtml          = toFlag elabHaddockHtml,
        haddockHtmlLocation  = maybe mempty toFlag elabHaddockHtmlLocation,
        haddockForHackage    = mempty, --TODO: new flag
        haddockForeignLibs   = toFlag elabHaddockForeignLibs,
        haddockExecutables   = toFlag elabHaddockExecutables,
        haddockTestSuites    = toFlag elabHaddockTestSuites,
        haddockBenchmarks    = toFlag elabHaddockBenchmarks,
        haddockInternal      = toFlag elabHaddockInternal,
        haddockCss           = maybe mempty toFlag elabHaddockCss,
        haddockHscolour      = toFlag elabHaddockHscolour,
        haddockHscolourCss   = maybe mempty toFlag elabHaddockHscolourCss,
        haddockContents      = maybe mempty toFlag elabHaddockContents,
        haddockDistPref      = toFlag builddir,
        haddockKeepTempFiles = mempty, --TODO: from build settings
        haddockVerbosity     = toFlag verbosity
      }
  
  {-
  setupHsTestFlags :: ElaboratedConfiguredPackage
                   -> ElaboratedSharedConfig
                   -> Verbosity
                   -> FilePath
                   -> Cabal.TestFlags
  setupHsTestFlags _ _ verbosity builddir =
      Cabal.TestFlags {
      }
  -}
  
  ------------------------------------------------------------------------------
  -- * Sharing installed packages
  ------------------------------------------------------------------------------
  
  --
  -- Nix style store management for tarball packages
  --
  -- So here's our strategy:
  --
  -- We use a per-user nix-style hashed store, but /only/ for tarball packages.
  -- So that includes packages from hackage repos (and other http and local
  -- tarballs). For packages in local directories we do not register them into
  -- the shared store by default, we just build them locally inplace.
  --
  -- The reason we do it like this is that it's easy to make stable hashes for
  -- tarball packages, and these packages benefit most from sharing. By contrast
  -- unpacked dir packages are harder to hash and they tend to change more
  -- frequently so there's less benefit to sharing them.
  --
  -- When using the nix store approach we have to run the solver *without*
  -- looking at the packages installed in the store, just at the source packages
  -- (plus core\/global installed packages). Then we do a post-processing pass
  -- to replace configured packages in the plan with pre-existing ones, where
  -- possible. Where possible of course means where the nix-style package hash
  -- equals one that's already in the store.
  --
  -- One extra wrinkle is that unless we know package tarball hashes upfront, we
  -- will have to download the tarballs to find their hashes. So we have two
  -- options: delay replacing source with pre-existing installed packages until
  -- the point during the execution of the install plan where we have the
  -- tarball, or try to do as much up-front as possible and then check again
  -- during plan execution. The former isn't great because we would end up
  -- telling users we're going to re-install loads of packages when in fact we
  -- would just share them. It'd be better to give as accurate a prediction as
  -- we can. The latter is better for users, but we do still have to check
  -- during plan execution because it's important that we don't replace existing
  -- installed packages even if they have the same package hash, because we
  -- don't guarantee ABI stability.
  
  -- TODO: [required eventually] for safety of concurrent installs, we must make sure we register but
  -- not replace installed packages with ghc-pkg.
  
  packageHashInputs :: ElaboratedSharedConfig
                    -> ElaboratedConfiguredPackage
                    -> PackageHashInputs
  packageHashInputs
      pkgshared
      elab@(ElaboratedConfiguredPackage {
        elabPkgSourceHash = Just srchash
      }) =
      PackageHashInputs {
        pkgHashPkgId       = packageId elab,
        pkgHashComponent   =
          case elabPkgOrComp elab of
            ElabPackage _ -> Nothing
            ElabComponent comp -> Just (compSolverName comp),
        pkgHashSourceHash  = srchash,
        -- pkgHashPkgConfigDeps = Set.fromList (elabPkgConfigDependencies elab),
        pkgHashDirectDeps  =
          case elabPkgOrComp elab of
            ElabPackage (ElaboratedPackage{..}) ->
              Set.fromList $
               [ confInstId dep
               | dep <- CD.select relevantDeps pkgLibDependencies ] ++
               [ confInstId dep
               | dep <- CD.select relevantDeps pkgExeDependencies ]
            ElabComponent comp ->
              Set.fromList (map confInstId (compLibDependencies comp
                                         ++ compExeDependencies comp)),
        pkgHashOtherConfig = packageHashConfigInputs pkgshared elab
      }
    where
      -- Obviously the main deps are relevant
      relevantDeps CD.ComponentLib       = True
      relevantDeps (CD.ComponentSubLib _) = True
      relevantDeps (CD.ComponentFLib _)   = True
      relevantDeps (CD.ComponentExe _)   = True
      -- Setup deps can affect the Setup.hs behaviour and thus what is built
      relevantDeps  CD.ComponentSetup    = True
      -- However testsuites and benchmarks do not get installed and should not
      -- affect the result, so we do not include them.
      relevantDeps (CD.ComponentTest  _) = False
      relevantDeps (CD.ComponentBench _) = False
  
  packageHashInputs _ pkg =
      error $ "packageHashInputs: only for packages with source hashes. "
           ++ display (packageId pkg)
  
  packageHashConfigInputs :: ElaboratedSharedConfig
                          -> ElaboratedConfiguredPackage
                          -> PackageHashConfigInputs
  packageHashConfigInputs
      ElaboratedSharedConfig{..}
      ElaboratedConfiguredPackage{..} =
  
      PackageHashConfigInputs {
        pkgHashCompilerId          = compilerId pkgConfigCompiler,
        pkgHashCompilerCommit      = compilerCommit pkgConfigCompiler,
        -- pkgHashPlatform            = pkgConfigPlatform,
        pkgHashFlagAssignment      = elabFlagAssignment,
        pkgHashConfigureScriptArgs = elabConfigureScriptArgs,
        pkgHashVanillaLib          = elabVanillaLib,
        pkgHashSharedLib           = elabSharedLib,
        pkgHashDynExe              = elabDynExe,
        pkgHashGHCiLib             = elabGHCiLib,
        pkgHashProfLib             = elabProfLib,
        pkgHashProfExe             = elabProfExe,
        pkgHashProfLibDetail       = elabProfLibDetail,
        pkgHashProfExeDetail       = elabProfExeDetail,
        pkgHashCoverage            = elabCoverage,
        pkgHashOptimization        = elabOptimization,
        pkgHashSplitObjs           = elabSplitObjs,
        pkgHashStripLibs           = elabStripLibs,
        pkgHashStripExes           = elabStripExes,
        pkgHashDebugInfo           = elabDebugInfo,
        pkgHashProgramArgs         = elabProgramArgs,
        pkgHashExtraLibDirs        = elabExtraLibDirs,
        pkgHashExtraFrameworkDirs  = elabExtraFrameworkDirs,
        pkgHashExtraIncludeDirs    = elabExtraIncludeDirs,
        pkgHashProgPrefix          = elabProgPrefix,
        pkgHashProgSuffix          = elabProgSuffix
      }
  
  
  -- | Given the 'InstalledPackageIndex' for a nix-style package store, and an
  -- 'ElaboratedInstallPlan', replace configured source packages by installed
  -- packages from the store whenever they exist.
  --
  improveInstallPlanWithInstalledPackages :: Set UnitId
                                          -> ElaboratedInstallPlan
                                          -> ElaboratedInstallPlan
  improveInstallPlanWithInstalledPackages installedPkgIdSet =
      InstallPlan.installed canPackageBeImproved
    where
      canPackageBeImproved pkg =
        installedUnitId pkg `Set.member` installedPkgIdSet
      --TODO: sanity checks:
      -- * the installed package must have the expected deps etc
      -- * the installed package must not be broken, valid dep closure
  
      --TODO: decide what to do if we encounter broken installed packages,
      -- since overwriting is never safe.
  
  
  -- Path construction
  ------
  
  -- | The path to the directory that contains a specific executable.
  -- NB: For inplace NOT InstallPaths.bindir installDirs; for an
  -- inplace build those values are utter nonsense.  So we
  -- have to guess where the directory is going to be.
  -- Fortunately this is "stable" part of Cabal API.
  -- But the way we get the build directory is A HORRIBLE
  -- HACK.
  binDirectoryFor
    :: DistDirLayout
    -> ElaboratedSharedConfig
    -> ElaboratedConfiguredPackage
    -> FilePath
    -> FilePath
  binDirectoryFor layout config package exe = case elabBuildStyle package of
    BuildAndInstall -> installedBinDirectory package
    BuildInplaceOnly -> inplaceBinRoot layout config package </> exe
  
  -- package has been built and installed.
  installedBinDirectory :: ElaboratedConfiguredPackage -> FilePath
  installedBinDirectory = InstallDirs.bindir . elabInstallDirs
  
  -- | The path to the @build@ directory for an inplace build.
  inplaceBinRoot
    :: DistDirLayout
    -> ElaboratedSharedConfig
    -> ElaboratedConfiguredPackage
    -> FilePath
  inplaceBinRoot layout config package
    =  distBuildDirectory layout (elabDistDirParams config package)
   </> "build"
  