content: {-# LANGUAGE CPP #-}
  {-# LANGUAGE RecordWildCards, NamedFieldPuns #-}
  {-# LANGUAGE RankNTypes, ScopedTypeVariables #-}
  
  -- | This module deals with building and incrementally rebuilding a collection
  -- of packages. It is what backs the @etlas build@ and @configure@ commands,
  -- as well as being a core part of @run@, @test@, @bench@ and others.
  --
  -- The primary thing is in fact rebuilding (and trying to make that quick by
  -- not redoing unnecessary work), so building from scratch is just a special
  -- case.
  --
  -- The build process and the code can be understood by breaking it down into
  -- three major parts:
  --
  -- * The 'ElaboratedInstallPlan' type
  --
  -- * The \"what to do\" phase, where we look at the all input configuration
  --   (project files, .cabal files, command line etc) and produce a detailed
  --   plan of what to do -- the 'ElaboratedInstallPlan'.
  --
  -- * The \"do it\" phase, where we take the 'ElaboratedInstallPlan' and we
  -- re-execute it.
  --
  -- As far as possible, the \"what to do\" phase embodies all the policy, leaving
  -- the \"do it\" phase policy free. The first phase contains more of the
  -- complicated logic, but it is contained in code that is either pure or just
  -- has read effects (except cache updates). Then the second phase does all the
  -- actions to build packages, but as far as possible it just follows the
  -- instructions and avoids any logic for deciding what to do (apart from
  -- recompilation avoidance in executing the plan).
  --
  -- This division helps us keep the code under control, making it easier to
  -- understand, test and debug. So when you are extending these modules, please
  -- think about which parts of your change belong in which part. It is
  -- perfectly ok to extend the description of what to do (i.e. the
  -- 'ElaboratedInstallPlan') if that helps keep the policy decisions in the
  -- first phase. Also, the second phase does not have direct access to any of
  -- the input configuration anyway; all the information has to flow via the
  -- 'ElaboratedInstallPlan'.
  --
  module Distribution.Client.ProjectOrchestration (
      -- * Discovery phase: what is in the project?
      establishProjectBaseContext,
      ProjectBaseContext(..),
      BuildTimeSettings(..),
      commandLineFlagsToProjectConfig,
  
      -- * Pre-build phase: decide what to do.
      withInstallPlan,
      runProjectPreBuildPhase,
      ProjectBuildContext(..),
  
      -- ** Selecting what targets we mean
      readTargetSelectors,
      reportTargetSelectorProblems,
      resolveTargets,
      TargetsMap,
      TargetSelector(..),
      PackageId,
      AvailableTarget(..),
      AvailableTargetStatus(..),
      TargetRequested(..),
      ComponentName(..),
      ComponentKind(..),
      ComponentTarget(..),
      SubComponentTarget(..),
      TargetProblemCommon(..),
      selectComponentTargetBasic,
      distinctTargetComponents,
      -- ** Utils for selecting targets
      filterTargetsKind,
      filterTargetsKindWith,
      selectBuildableTargets,
      selectBuildableTargetsWith,
      selectBuildableTargets',
      selectBuildableTargetsWith',
      forgetTargetsDetail,
  
      -- ** Adjusting the plan
      pruneInstallPlanToTargets,
      TargetAction(..),
      pruneInstallPlanToDependencies,
      CannotPruneDependencies(..),
      printPlan,
  
      -- * Build phase: now do it.
      runProjectBuildPhase,
  
      -- * Post build actions
      runProjectPostBuildPhase,
      dieOnBuildFailures,
  
      -- * Shared CLI utils
      cmdCommonHelpTextNewBuildBeta,
    ) where
  
  import           Distribution.Client.ProjectConfig
  import           Distribution.Client.ProjectPlanning
                     hiding ( pruneInstallPlanToTargets )
  import qualified Distribution.Client.ProjectPlanning as ProjectPlanning
                     ( pruneInstallPlanToTargets )
  import           Distribution.Client.ProjectPlanning.Types
  import           Distribution.Client.ProjectBuilding
  import           Distribution.Client.ProjectPlanOutput
  
  import           Distribution.Client.Types
                     ( GenericReadyPackage(..), UnresolvedSourcePackage
                     , PackageSpecifier(..), SourcePackageDb(..) )
  import           Distribution.Solver.Types.PackageIndex
                    ( lookupPackageName )
  import qualified Distribution.Client.InstallPlan as InstallPlan
  import           Distribution.Client.TargetSelector
                     ( TargetSelector(..)
                     , ComponentKind(..), componentKind
                     , readTargetSelectors, reportTargetSelectorProblems )
  import           Distribution.Client.DistDirLayout
  import           Distribution.Client.Config (defaultCabalDir)
  import           Distribution.Client.Setup hiding (packageName)
  import           Distribution.Types.ComponentName
                     ( componentNameString )
  import           Distribution.Types.UnqualComponentName
                     ( UnqualComponentName, packageNameToUnqualComponentName )
  -- import           Distribution.Client.Types
  import           Distribution.Solver.Types.OptionalStanza
  
  import           Distribution.Package
                     hiding (InstalledPackageId, installedPackageId)
  import           Distribution.PackageDescription (FlagAssignment, showFlagValue)
  import           Distribution.Simple.LocalBuildInfo
                     ( ComponentName(..), pkgComponents )
  import qualified Distribution.Simple.Setup as Setup
  import           Distribution.Simple.Command (commandShowOptions)
  
  import           Distribution.Simple.Utils
                     ( die'
                     , notice, noticeNoWrap, debugNoWrap )
  import           Distribution.Verbosity
  import           Distribution.Text
  
  import qualified Data.Monoid as Mon
  import qualified Data.Set as Set
  import qualified Data.Map as Map
  import           Data.Map (Map)
  import           Data.List
  import           Data.Maybe
  import           Data.Either
  import           Control.Exception (Exception(..), throwIO, assert)
  import           System.Exit (ExitCode(..), exitFailure)
  #ifdef MIN_VERSION_unix
  import           System.Posix.Signals (sigKILL, sigSEGV)
  #endif
  
  
  -- | This holds the context of a project prior to solving: the content of the
  -- @cabal.project@ and all the local package @.cabal@ files.
  --
  data ProjectBaseContext = ProjectBaseContext {
         distDirLayout  :: DistDirLayout,
         cabalDirLayout :: CabalDirLayout,
         projectConfig  :: ProjectConfig,
         localPackages  :: [PackageSpecifier UnresolvedSourcePackage],
         buildSettings  :: BuildTimeSettings
       }
  
  establishProjectBaseContext :: Verbosity
                              -> ProjectConfig
                              -> IO ProjectBaseContext
  establishProjectBaseContext verbosity cliConfig = do
  
      cabalDir <- defaultCabalDir
      projectRoot <- either throwIO return =<<
                     findProjectRoot Nothing mprojectFile
  
      let distDirLayout  = defaultDistDirLayout projectRoot
                                                mdistDirectory
  
      (projectConfig, localPackages) <-
        rebuildProjectConfig verbosity
                             distDirLayout
                             cliConfig
  
      let ProjectConfigBuildOnly {
            projectConfigLogsDir,
            projectConfigStoreDir
          } = projectConfigBuildOnly projectConfig
  
          mlogsDir = Setup.flagToMaybe projectConfigLogsDir
          mstoreDir = Setup.flagToMaybe projectConfigStoreDir
          cabalDirLayout = mkCabalDirLayout cabalDir mstoreDir mlogsDir
  
          buildSettings = resolveBuildTimeSettings
                            verbosity cabalDirLayout
                            projectConfig
  
      return ProjectBaseContext {
        distDirLayout,
        cabalDirLayout,
        projectConfig,
        localPackages,
        buildSettings
      }
    where
      mdistDirectory = Setup.flagToMaybe projectConfigDistDir
      mprojectFile   = Setup.flagToMaybe projectConfigProjectFile
      ProjectConfigShared {
        projectConfigDistDir,
        projectConfigProjectFile
      } = projectConfigShared cliConfig
  
  
  -- | This holds the context between the pre-build, build and post-build phases.
  --
  data ProjectBuildContext = ProjectBuildContext {
        -- | This is the improved plan, before we select a plan subset based on
        -- the build targets, and before we do the dry-run. So this contains
        -- all packages in the project.
        elaboratedPlanOriginal :: ElaboratedInstallPlan,
  
        -- | This is the 'elaboratedPlanOriginal' after we select a plan subset
        -- and do the dry-run phase to find out what is up-to or out-of date.
        -- This is the plan that will be executed during the build phase. So
        -- this contains only a subset of packages in the project.
        elaboratedPlanToExecute:: ElaboratedInstallPlan,
  
        -- | The part of the install plan that's shared between all packages in
        -- the plan. This does not change between the two plan variants above,
        -- so there is just the one copy.
        elaboratedShared       :: ElaboratedSharedConfig,
  
        -- | The result of the dry-run phase. This tells us about each member of
        -- the 'elaboratedPlanToExecute'.
        pkgsBuildStatus        :: BuildStatusMap,
  
        -- | The targets selected by @selectPlanSubset@. This is useful eg. in
        -- CmdRun, where we need a valid target to execute.
        targetsMap             :: TargetsMap
      }
  
  -- | Pre-build phase: decide what to do.
  --
  withInstallPlan
      :: Verbosity
      -> ProjectBaseContext
      -> (ElaboratedInstallPlan -> ElaboratedSharedConfig -> IO a)
      -> IO a
  withInstallPlan
      verbosity
      ProjectBaseContext {
        distDirLayout,
        cabalDirLayout,
        projectConfig,
        localPackages
      }
      action = do
      -- Take the project configuration and make a plan for how to build
      -- everything in the project. This is independent of any specific targets
      -- the user has asked for.
      --
      (elaboratedPlan, _, elaboratedShared) <-
        rebuildInstallPlan verbosity
                           distDirLayout cabalDirLayout
                           projectConfig
                           localPackages
      action elaboratedPlan elaboratedShared
  
  
  -- | Pre-build phase: decide what to do.
  --
  runProjectPreBuildPhase
      :: Verbosity
      -> ProjectBaseContext
      -> (ElaboratedInstallPlan -> IO (ElaboratedInstallPlan, TargetsMap, a))
      -> IO (ProjectBuildContext, a)
  runProjectPreBuildPhase
      verbosity
      ProjectBaseContext {
        distDirLayout,
        cabalDirLayout,
        projectConfig,
        localPackages
      }
      selectPlanSubset = do
  
      -- Take the project configuration and make a plan for how to build
      -- everything in the project. This is independent of any specific targets
      -- the user has asked for.
      --
      (elaboratedPlan, _, elaboratedShared) <-
        rebuildInstallPlan verbosity
                           distDirLayout cabalDirLayout
                           projectConfig
                           localPackages
  
      -- The plan for what to do is represented by an 'ElaboratedInstallPlan'
  
      -- Now given the specific targets the user has asked for, decide
      -- which bits of the plan we will want to execute.
      --
      (elaboratedPlan', targets, a) <- selectPlanSubset elaboratedPlan
  
      -- Check which packages need rebuilding.
      -- This also gives us more accurate reasons for the --dry-run output.
      --
      pkgsBuildStatus <- rebuildTargetsDryRun distDirLayout elaboratedShared
                                              elaboratedPlan'
  
      -- Improve the plan by marking up-to-date packages as installed.
      --
      let elaboratedPlan'' = improveInstallPlanWithUpToDatePackages
                               pkgsBuildStatus elaboratedPlan'
      debugNoWrap verbosity (InstallPlan.showInstallPlan elaboratedPlan'')
  
      return (ProjectBuildContext {
                 elaboratedPlanOriginal = elaboratedPlan,
                 elaboratedPlanToExecute = elaboratedPlan'',
                 elaboratedShared,
                 pkgsBuildStatus,
                 targetsMap = targets
                 }, a)
  
  
  -- | Build phase: now do it.
  --
  -- Execute all or parts of the description of what to do to build or
  -- rebuild the various packages needed.
  --
  runProjectBuildPhase :: Verbosity
                       -> ProjectBaseContext
                       -> ProjectBuildContext
                       -> IO BuildOutcomes
  runProjectBuildPhase _ ProjectBaseContext{buildSettings} _
    | buildSettingDryRun buildSettings
    = return Map.empty
  
  runProjectBuildPhase verbosity
                       ProjectBaseContext{..} ProjectBuildContext {..} =
      fmap (Map.union (previousBuildOutcomes pkgsBuildStatus)) $
      rebuildTargets verbosity
                     distDirLayout
                     (cabalStoreDirLayout cabalDirLayout)
                     elaboratedPlanToExecute
                     elaboratedShared
                     pkgsBuildStatus
                     buildSettings
    where
      previousBuildOutcomes :: BuildStatusMap -> BuildOutcomes
      previousBuildOutcomes =
        Map.mapMaybe $ \status -> case status of
          BuildStatusUpToDate buildSuccess -> Just (Right buildSuccess)
          --TODO: [nice to have] record build failures persistently
          _                                  -> Nothing
  
  -- | Post-build phase: various administrative tasks
  --
  -- Update bits of state based on the build outcomes and report any failures.
  --
  runProjectPostBuildPhase :: Verbosity
                           -> ProjectBaseContext
                           -> ProjectBuildContext
                           -> BuildOutcomes
                           -> IO ()
  runProjectPostBuildPhase _ ProjectBaseContext{buildSettings} _ _
    | buildSettingDryRun buildSettings
    = return ()
  
  runProjectPostBuildPhase verbosity
                           ProjectBaseContext {..} ProjectBuildContext {..}
                           buildOutcomes = do
      -- Update other build artefacts
      -- TODO: currently none, but could include:
      --        - bin symlinks/wrappers
      --        - haddock/hoogle/ctags indexes
      --        - delete stale lib registrations
      --        - delete stale package dirs
  
      postBuildStatus <- updatePostBuildProjectStatus
                           verbosity
                           distDirLayout
                           elaboratedPlanOriginal
                           pkgsBuildStatus
                           buildOutcomes
  
      writePlanGhcEnvironment distDirLayout
                              elaboratedPlanOriginal
                              elaboratedShared
                              postBuildStatus
  
      -- Finally if there were any build failures then report them and throw
      -- an exception to terminate the program
      dieOnBuildFailures verbosity elaboratedPlanToExecute buildOutcomes
  
      -- Note that it is a deliberate design choice that the 'buildTargets' is
      -- not passed to phase 1, and the various bits of input config is not
      -- passed to phase 2.
      --
      -- We make the install plan without looking at the particular targets the
      -- user asks us to build. The set of available things we can build is
      -- discovered from the env and config and is used to make the install plan.
      -- The targets just tell us which parts of the install plan to execute.
      --
      -- Conversely, executing the plan does not directly depend on any of the
      -- input config. The bits that are needed (or better, the decisions based
      -- on it) all go into the install plan.
  
      -- Notionally, the 'BuildFlags' should be things that do not affect what
      -- we build, just how we do it. These ones of course do
  
  
  ------------------------------------------------------------------------------
  -- Taking targets into account, selecting what to build
  --
  
  -- | The set of components to build, represented as a mapping from 'UnitId's
  -- to the 'ComponentTarget's within the unit that will be selected
  -- (e.g. selected to build, test or repl).
  --
  -- Associated with each 'ComponentTarget' is the set of 'TargetSelector's that
  -- matched this target. Typically this is exactly one, but in general it is
  -- possible to for different selectors to match the same target. This extra
  -- information is primarily to help make helpful error messages.
  --
  type TargetsMap = Map UnitId [(ComponentTarget, [TargetSelector])]
  
  -- | Given a set of 'TargetSelector's, resolve which 'UnitId's and
  -- 'ComponentTarget's they ought to refer to.
  --
  -- The idea is that every user target identifies one or more roots in the
  -- 'ElaboratedInstallPlan', which we will use to determine the closure
  -- of what packages need to be built, dropping everything from the plan
  -- that is unnecessary. This closure and pruning is done by
  -- 'pruneInstallPlanToTargets' and this needs to be told the roots in terms
  -- of 'UnitId's and the 'ComponentTarget's within those.
  --
  -- This means we first need to translate the 'TargetSelector's into the
  -- 'UnitId's and 'ComponentTarget's. This translation has to be different for
  -- the different command line commands, like @build@, @repl@ etc. For example
  -- the command @build pkgfoo@ could select a different set of components in
  -- pkgfoo than @repl pkgfoo@. The @build@ command would select any library and
  -- all executables, whereas @repl@ would select the library or a single
  -- executable. Furthermore, both of these examples could fail, and fail in
  -- different ways and each needs to be able to produce helpful error messages.
  --
  -- So 'resolveTargets' takes two helpers: one to select the targets to be used
  -- by user targets that refer to a whole package ('TargetPackage'), and
  -- another to check user targets that refer to a component (or a module or
  -- file within a component). These helpers can fail, and use their own error
  -- type. Both helpers get given the 'AvailableTarget' info about the
  -- component(s).
  --
  -- While commands vary quite a bit in their behaviour about which components to
  -- select for a whole-package target, most commands have the same behaviour for
  -- checking a user target that refers to a specific component. To help with
  -- this commands can use 'selectComponentTargetBasic', either directly or as
  -- a basis for their own @selectComponentTarget@ implementation.
  --
  resolveTargets :: forall err.
                    (forall k. TargetSelector
                            -> [AvailableTarget k]
                            -> Either err [k])
                 -> (forall k. SubComponentTarget
                            -> AvailableTarget k
                            -> Either err  k )
                 -> (TargetProblemCommon -> err)
                 -> ElaboratedInstallPlan
                 -> Maybe (SourcePackageDb)
                 -> [TargetSelector]
                 -> Either [err] TargetsMap
  resolveTargets selectPackageTargets selectComponentTarget liftProblem
                 installPlan mPkgDb =
        fmap mkTargetsMap
      . checkErrors
      . map (\ts -> (,) ts <$> checkTarget ts)
    where
      mkTargetsMap :: [(TargetSelector, [(UnitId, ComponentTarget)])]
                   -> TargetsMap
      mkTargetsMap targets =
          Map.map nubComponentTargets
        $ Map.fromListWith (++)
            [ (uid, [(ct, ts)])
            | (ts, cts) <- targets
            , (uid, ct) <- cts ]
  
      AvailableTargetIndexes{..} = availableTargetIndexes installPlan
  
      checkTarget :: TargetSelector -> Either err [(UnitId, ComponentTarget)]
  
      -- We can ask to build any whole package, project-local or a dependency
      checkTarget bt@(TargetPackage _ [pkgid] mkfilter)
        | Just ats <- fmap (maybe id filterTargetsKind mkfilter)
                    $ Map.lookup pkgid availableTargetsByPackageId
        = fmap (componentTargets WholeComponent)
        $ selectPackageTargets bt ats
  
        | otherwise
        = Left (liftProblem (TargetProblemNoSuchPackage pkgid))
  
      checkTarget (TargetPackage _ _ _)
        = error "TODO: add support for multiple packages in a directory"
        -- For the moment this error cannot happen here, because it gets
        -- detected when the package config is being constructed. This case
        -- will need handling properly when we do add support.
        --
        -- TODO: how should this use case play together with the
        -- '--cabal-file' option of 'configure' which allows using multiple
        -- .cabal files for a single package?
  
      checkTarget bt@(TargetAllPackages mkfilter) =
          fmap (componentTargets WholeComponent)
        . selectPackageTargets bt
        . maybe id filterTargetsKind mkfilter
        . filter availableTargetLocalToProject
        $ concat (Map.elems availableTargetsByPackageId)
  
      checkTarget (TargetComponent pkgid cname subtarget)
        | Just ats <- Map.lookup (pkgid, cname)
                                 availableTargetsByPackageIdAndComponentName
        = fmap (componentTargets subtarget)
        $ selectComponentTargets subtarget ats
  
        | Map.member pkgid availableTargetsByPackageId
        = Left (liftProblem (TargetProblemNoSuchComponent pkgid cname))
  
        | otherwise
        = Left (liftProblem (TargetProblemNoSuchPackage pkgid))
  
      checkTarget (TargetComponentUnknown pkgname ecname subtarget)
        | Just ats <- case ecname of
            Left ucname ->
              Map.lookup (pkgname, ucname)
                         availableTargetsByPackageNameAndUnqualComponentName
            Right cname ->
              Map.lookup (pkgname, cname)
                         availableTargetsByPackageNameAndComponentName
        = fmap (componentTargets subtarget)
        $ selectComponentTargets subtarget ats
  
        | Map.member pkgname availableTargetsByPackageName
        = Left (liftProblem (TargetProblemUnknownComponent pkgname ecname))
  
        | otherwise
        = Left (liftProblem (TargetNotInProject pkgname))
  
      checkTarget bt@(TargetPackageNamed pkgname mkfilter)
        | Just ats <- fmap (maybe id filterTargetsKind mkfilter)
                    $ Map.lookup pkgname availableTargetsByPackageName
        = fmap (componentTargets WholeComponent)
        . selectPackageTargets bt
        $ ats
  
        | Just SourcePackageDb{ packageIndex } <- mPkgDb
        , let pkg = lookupPackageName packageIndex pkgname
        , not (null pkg)
        = Left (liftProblem (TargetAvailableInIndex pkgname))
  
        | otherwise
        = Left (liftProblem (TargetNotInProject pkgname))
  
      componentTargets :: SubComponentTarget
                       -> [(b, ComponentName)]
                       -> [(b, ComponentTarget)]
      componentTargets subtarget =
        map (fmap (\cname -> ComponentTarget cname subtarget))
  
      selectComponentTargets :: SubComponentTarget
                             -> [AvailableTarget k]
                             -> Either err [k]
      selectComponentTargets subtarget =
          either (Left . head) Right
        . checkErrors
        . map (selectComponentTarget subtarget)
  
      checkErrors :: [Either e a] -> Either [e] [a]
      checkErrors = (\(es, xs) -> if null es then Right xs else Left es)
                  . partitionEithers
  
  
  data AvailableTargetIndexes = AvailableTargetIndexes {
         availableTargetsByPackageIdAndComponentName
           :: AvailableTargetsMap (PackageId, ComponentName),
  
         availableTargetsByPackageId
           :: AvailableTargetsMap PackageId,
  
         availableTargetsByPackageName
           :: AvailableTargetsMap PackageName,
  
         availableTargetsByPackageNameAndComponentName
           :: AvailableTargetsMap (PackageName, ComponentName),
  
         availableTargetsByPackageNameAndUnqualComponentName
           :: AvailableTargetsMap (PackageName, UnqualComponentName)
       }
  type AvailableTargetsMap k = Map k [AvailableTarget (UnitId, ComponentName)]
  
  -- We define a bunch of indexes to help 'resolveTargets' with resolving
  -- 'TargetSelector's to specific 'UnitId's.
  --
  -- They are all derived from the 'availableTargets' index.
  -- The 'availableTargetsByPackageIdAndComponentName' is just that main index,
  -- while the others are derived by re-grouping on the index key.
  --
  -- They are all constructed lazily because they are not necessarily all used.
  --
  availableTargetIndexes :: ElaboratedInstallPlan -> AvailableTargetIndexes
  availableTargetIndexes installPlan = AvailableTargetIndexes{..}
    where
      availableTargetsByPackageIdAndComponentName =
        availableTargets installPlan
  
      availableTargetsByPackageId =
                    Map.mapKeysWith
                      (++) (\(pkgid, _cname) -> pkgid)
                      availableTargetsByPackageIdAndComponentName
        `Map.union` availableTargetsEmptyPackages
  
      availableTargetsByPackageName =
        Map.mapKeysWith
          (++) packageName
          availableTargetsByPackageId
  
      availableTargetsByPackageNameAndComponentName =
        Map.mapKeysWith
          (++) (\(pkgid, cname) -> (packageName pkgid, cname))
          availableTargetsByPackageIdAndComponentName
  
      availableTargetsByPackageNameAndUnqualComponentName =
        Map.mapKeysWith
          (++) (\(pkgid, cname) -> let pname  = packageName pkgid
                                       cname' = unqualComponentName pname cname
                                    in (pname, cname'))
          availableTargetsByPackageIdAndComponentName
       where
         unqualComponentName :: PackageName -> ComponentName -> UnqualComponentName
         unqualComponentName pkgname =
             fromMaybe (packageNameToUnqualComponentName pkgname)
           . componentNameString
  
      -- Add in all the empty packages. These do not appear in the
      -- availableTargetsByComponent map, since that only contains components
      -- so packages with no components are invisible from that perspective.
      -- The empty packages need to be there for proper error reporting, so users
      -- can select the empty package and then we can report that it is empty,
      -- otherwise we falsely report there is no such package at all.
      availableTargetsEmptyPackages =
        Map.fromList
          [ (packageId pkg, [])
          | InstallPlan.Configured pkg <- InstallPlan.toList installPlan
          , case elabPkgOrComp pkg of
              ElabComponent _ -> False
              ElabPackage   _ -> null (pkgComponents (elabPkgDescription pkg))
          ]
  
      --TODO: [research required] what if the solution has multiple versions of this package?
      --      e.g. due to setup deps or due to multiple independent sets of
      --      packages being built (e.g. ghc + ghcjs in a project)
  
  filterTargetsKind :: ComponentKind -> [AvailableTarget k] -> [AvailableTarget k]
  filterTargetsKind ckind = filterTargetsKindWith (== ckind)
  
  filterTargetsKindWith :: (ComponentKind -> Bool)
                       -> [AvailableTarget k] -> [AvailableTarget k]
  filterTargetsKindWith p ts =
      [ t | t@(AvailableTarget _ cname _ _) <- ts
          , p (componentKind cname) ]
  
  selectBuildableTargets :: [AvailableTarget k] -> [k]
  selectBuildableTargets ts =
      [ k | AvailableTarget _ _ (TargetBuildable k _) _ <- ts ]
  
  selectBuildableTargetsWith :: (TargetRequested -> Bool)
                            -> [AvailableTarget k] -> [k]
  selectBuildableTargetsWith p ts =
      [ k | AvailableTarget _ _ (TargetBuildable k req) _ <- ts, p req ]
  
  selectBuildableTargets' :: [AvailableTarget k] -> ([k], [AvailableTarget ()])
  selectBuildableTargets' ts =
      (,) [ k | AvailableTarget _ _ (TargetBuildable k _) _ <- ts ]
          [ forgetTargetDetail t
          | t@(AvailableTarget _ _ (TargetBuildable _ _) _) <- ts ]
  
  selectBuildableTargetsWith' :: (TargetRequested -> Bool)
                             -> [AvailableTarget k] -> ([k], [AvailableTarget ()])
  selectBuildableTargetsWith' p ts =
      (,) [ k | AvailableTarget _ _ (TargetBuildable k req) _ <- ts, p req ]
          [ forgetTargetDetail t
          | t@(AvailableTarget _ _ (TargetBuildable _ req) _) <- ts, p req ]
  
  
  forgetTargetDetail :: AvailableTarget k -> AvailableTarget ()
  forgetTargetDetail = fmap (const ())
  
  forgetTargetsDetail :: [AvailableTarget k] -> [AvailableTarget ()]
  forgetTargetsDetail = map forgetTargetDetail
  
  -- | A basic @selectComponentTarget@ implementation to use or pass to
  -- 'resolveTargets', that does the basic checks that the component is
  -- buildable and isn't a test suite or benchmark that is disabled. This
  -- can also be used to do these basic checks as part of a custom impl that
  --
  selectComponentTargetBasic :: SubComponentTarget
                             -> AvailableTarget k
                             -> Either TargetProblemCommon k
  selectComponentTargetBasic subtarget
                             AvailableTarget {
                               availableTargetPackageId     = pkgid,
                               availableTargetComponentName = cname,
                               availableTargetStatus
                             } =
      case availableTargetStatus of
        TargetDisabledByUser ->
          Left (TargetOptionalStanzaDisabledByUser pkgid cname subtarget)
  
        TargetDisabledBySolver ->
          Left (TargetOptionalStanzaDisabledBySolver pkgid cname subtarget)
  
        TargetNotLocal ->
          Left (TargetComponentNotProjectLocal pkgid cname subtarget)
  
        TargetNotBuildable ->
          Left (TargetComponentNotBuildable pkgid cname subtarget)
  
        TargetBuildable targetKey _ ->
          Right targetKey
  
  data TargetProblemCommon
     = TargetNotInProject                   PackageName
     | TargetAvailableInIndex               PackageName
     | TargetComponentNotProjectLocal       PackageId ComponentName SubComponentTarget
     | TargetComponentNotBuildable          PackageId ComponentName SubComponentTarget
     | TargetOptionalStanzaDisabledByUser   PackageId ComponentName SubComponentTarget
     | TargetOptionalStanzaDisabledBySolver PackageId ComponentName SubComponentTarget
     | TargetProblemUnknownComponent        PackageName
                                            (Either UnqualComponentName ComponentName)
  
      -- The target matching stuff only returns packages local to the project,
      -- so these lookups should never fail, but if 'resolveTargets' is called
      -- directly then of course it can.
     | TargetProblemNoSuchPackage           PackageId
     | TargetProblemNoSuchComponent         PackageId ComponentName
    deriving (Eq, Show)
  
  -- | Wrapper around 'ProjectPlanning.pruneInstallPlanToTargets' that adjusts
  -- for the extra unneeded info in the 'TargetsMap'.
  --
  pruneInstallPlanToTargets :: TargetAction -> TargetsMap
                            -> ElaboratedInstallPlan -> ElaboratedInstallPlan
  pruneInstallPlanToTargets targetActionType targetsMap elaboratedPlan =
      assert (Map.size targetsMap > 0) $
      ProjectPlanning.pruneInstallPlanToTargets
        targetActionType
        (Map.map (map fst) targetsMap)
        elaboratedPlan
  
  -- | Utility used by repl and run to check if the targets spans multiple
  -- components, since those commands do not support multiple components.
  --
  distinctTargetComponents :: TargetsMap -> Set.Set (UnitId, ComponentName)
  distinctTargetComponents targetsMap =
      Set.fromList [ (uid, cname)
                   | (uid, cts) <- Map.toList targetsMap
                   , (ComponentTarget cname _, _) <- cts ]
  
  
  ------------------------------------------------------------------------------
  -- Displaying what we plan to do
  --
  
  -- | Print a user-oriented presentation of the install plan, indicating what
  -- will be built.
  --
  printPlan :: Verbosity
            -> ProjectBaseContext
            -> ProjectBuildContext
            -> IO ()
  printPlan verbosity
            ProjectBaseContext {
              buildSettings = BuildTimeSettings{buildSettingDryRun}
            }
            ProjectBuildContext {
              elaboratedPlanToExecute = elaboratedPlan,
              elaboratedShared,
              pkgsBuildStatus
            }
  
    | null pkgs
    = notice verbosity "Up to date"
  
    | otherwise
    = noticeNoWrap verbosity $ unlines $
        ("In order, the following " ++ wouldWill ++ " be built" ++
        ifNormal " (use -v for more details)" ++ ":")
      : map showPkgAndReason pkgs
  
    where
      pkgs = InstallPlan.executionOrder elaboratedPlan
  
      ifVerbose s | verbosity >= verbose = s
                  | otherwise            = ""
  
      ifNormal s | verbosity >= verbose = ""
                 | otherwise            = s
  
      wouldWill | buildSettingDryRun = "would"
                | otherwise          = "will"
  
      showPkgAndReason :: ElaboratedReadyPackage -> String
      showPkgAndReason (ReadyPackage elab) =
        " - " ++
        (if verbosity >= deafening
          then display (installedUnitId elab)
          else display (packageId elab)
          ) ++
        (case elabPkgOrComp elab of
            ElabPackage pkg -> showTargets elab ++ ifVerbose (showStanzas pkg)
            ElabComponent comp ->
              " (" ++ showComp elab comp ++ ")"
              ) ++
        showFlagAssignment (nonDefaultFlags elab) ++
        showConfigureFlags elab ++
        let buildStatus = pkgsBuildStatus Map.! installedUnitId elab in
        " (" ++ showBuildStatus buildStatus ++ ")"
  
      showComp elab comp =
          maybe "custom" display (compComponentName comp) ++
          if Map.null (elabInstantiatedWith elab)
              then ""
              else " with " ++
                  intercalate ", "
                      -- TODO: Abbreviate the UnitIds
                      [ display k ++ "=" ++ display v
                      | (k,v) <- Map.toList (elabInstantiatedWith elab) ]
  
      nonDefaultFlags :: ElaboratedConfiguredPackage -> FlagAssignment
      nonDefaultFlags elab = elabFlagAssignment elab \\ elabFlagDefaults elab
  
      showStanzas pkg = concat
                      $ [ " *test"
                        | TestStanzas  `Set.member` pkgStanzasEnabled pkg ]
                     ++ [ " *bench"
                        | BenchStanzas `Set.member` pkgStanzasEnabled pkg ]
  
      showTargets elab
        | null (elabBuildTargets elab) = ""
        | otherwise
        = " (" ++ intercalate ", " [ showComponentTarget (packageId elab) t | t <- elabBuildTargets elab ]
               ++ ")"
  
      showFlagAssignment :: FlagAssignment -> String
      showFlagAssignment = concatMap ((' ' :) . showFlagValue)
  
      showConfigureFlags elab =
          let fullConfigureFlags
                = setupHsConfigureFlags
                      (ReadyPackage elab)
                      elaboratedShared
                      verbosity
                      "$builddir"
              -- | Given a default value @x@ for a flag, nub @Flag x@
              -- into @NoFlag@.  This gives us a tidier command line
              -- rendering.
              nubFlag :: Eq a => a -> Setup.Flag a -> Setup.Flag a
              nubFlag x (Setup.Flag x') | x == x' = Setup.NoFlag
              nubFlag _ f = f
              -- TODO: Closely logic from 'configureProfiling'.
              tryExeProfiling = Setup.fromFlagOrDefault False
                                  (configProf fullConfigureFlags)
              tryLibProfiling = Setup.fromFlagOrDefault False
                                  (Mon.mappend (configProf    fullConfigureFlags)
                                               (configProfExe fullConfigureFlags))
              partialConfigureFlags
                = Mon.mempty {
                  configProf    =
                      nubFlag False (configProf fullConfigureFlags),
                  configProfExe =
                      nubFlag tryExeProfiling (configProfExe fullConfigureFlags),
                  configProfLib =
                      nubFlag tryLibProfiling (configProfLib fullConfigureFlags)
                  -- Maybe there are more we can add
                }
          -- Not necessary to "escape" it, it's just for user output
          in unwords . ("":) $
              commandShowOptions
              (Setup.configureCommand (pkgConfigCompilerProgs elaboratedShared))
              partialConfigureFlags
  
      showBuildStatus status = case status of
        BuildStatusPreExisting -> "existing package"
        BuildStatusInstalled   -> "already installed"
        BuildStatusDownload {} -> "requires download & build"
        BuildStatusUnpack   {} -> "requires build"
        BuildStatusRebuild _ rebuild -> case rebuild of
          BuildStatusConfigure
            (MonitoredValueChanged _)   -> "configuration changed"
          BuildStatusConfigure mreason  -> showMonitorChangedReason mreason
          BuildStatusBuild _ buildreason -> case buildreason of
            BuildReasonDepsRebuilt      -> "dependency rebuilt"
            BuildReasonFilesChanged
              mreason                   -> showMonitorChangedReason mreason
            BuildReasonExtraTargets _   -> "additional components to build"
            BuildReasonEphemeralTargets -> "ephemeral targets"
        BuildStatusUpToDate {} -> "up to date" -- doesn't happen
  
      showMonitorChangedReason (MonitoredFileChanged file) = "file " ++ file ++ " changed"
      showMonitorChangedReason (MonitoredValueChanged _)   = "value changed"
      showMonitorChangedReason  MonitorFirstRun     = "first run"
      showMonitorChangedReason  MonitorCorruptCache = "cannot read state cache"
  
  
  -- | If there are build failures then report them and throw an exception.
  --
  dieOnBuildFailures :: Verbosity
                     -> ElaboratedInstallPlan -> BuildOutcomes -> IO ()
  dieOnBuildFailures verbosity plan buildOutcomes
    | null failures = return ()
  
    | isSimpleCase  = exitFailure
  
    | otherwise = do
        -- For failures where we have a build log, print the log plus a header
         sequence_
           [ do notice verbosity $
                  '\n' : renderFailureDetail False pkg reason
                      ++ "\nBuild log ( " ++ logfile ++ " ):"
                readFile logfile >>= noticeNoWrap verbosity
           | (pkg, ShowBuildSummaryAndLog reason logfile)
               <- failuresClassification
           ]
  
         -- For all failures, print either a short summary (if we showed the
         -- build log) or all details
         die' verbosity $ unlines
           [ case failureClassification of
               ShowBuildSummaryAndLog reason _
                 | verbosity > normal
                -> renderFailureDetail mentionDepOf pkg reason
  
                 | otherwise
                -> renderFailureSummary mentionDepOf pkg reason
                ++ ". See the build log above for details."
  
               ShowBuildSummaryOnly reason ->
                 renderFailureDetail mentionDepOf pkg reason
  
           | let mentionDepOf = verbosity <= normal
           , (pkg, failureClassification) <- failuresClassification ]
    where
      failures =  [ (pkgid, failure)
                  | (pkgid, Left failure) <- Map.toList buildOutcomes ]
  
      failuresClassification =
        [ (pkg, classifyBuildFailure failure)
        | (pkgid, failure) <- failures
        , case buildFailureReason failure of
            DependentFailed {} -> verbosity > normal
            _                  -> True
        , InstallPlan.Configured pkg <-
             maybeToList (InstallPlan.lookup plan pkgid)
        ]
  
      classifyBuildFailure :: BuildFailure -> BuildFailurePresentation
      classifyBuildFailure BuildFailure {
                             buildFailureReason  = reason,
                             buildFailureLogFile = mlogfile
                           } =
        maybe (ShowBuildSummaryOnly   reason)
              (ShowBuildSummaryAndLog reason) $ do
          logfile <- mlogfile
          e       <- buildFailureException reason
          ExitFailure 1 <- fromException e
          return logfile
  
      -- Special case: we don't want to report anything complicated in the case
      -- of just doing build on the current package, since it's clear from
      -- context which package failed.
      --
      -- We generalise this rule as follows:
      --  - if only one failure occurs, and it is in a single root package (ie a
      --    package with nothing else depending on it)
      --  - and that failure is of a kind that always reports enough detail
      --    itself (e.g. ghc reporting errors on stdout)
      --  - then we do not report additional error detail or context.
      --
      isSimpleCase
        | [(pkgid, failure)] <- failures
        , [pkg]              <- rootpkgs
        , installedUnitId pkg == pkgid
        , isFailureSelfExplanatory (buildFailureReason failure)
        = True
        | otherwise
        = False
  
      -- NB: if the Setup script segfaulted or was interrupted,
      -- we should give more detailed information.  So only
      -- assume that exit code 1 is "pedestrian failure."
      isFailureSelfExplanatory (BuildFailed e)
        | Just (ExitFailure 1) <- fromException e = True
  
      isFailureSelfExplanatory (ConfigureFailed e)
        | Just (ExitFailure 1) <- fromException e = True
  
      isFailureSelfExplanatory _                  = False
  
      rootpkgs =
        [ pkg
        | InstallPlan.Configured pkg <- InstallPlan.toList plan
        , hasNoDependents pkg ]
  
      ultimateDeps pkgid =
          filter (\pkg -> hasNoDependents pkg && installedUnitId pkg /= pkgid)
                 (InstallPlan.reverseDependencyClosure plan [pkgid])
  
      hasNoDependents :: HasUnitId pkg => pkg -> Bool
      hasNoDependents = null . InstallPlan.revDirectDeps plan . installedUnitId
  
      renderFailureDetail mentionDepOf pkg reason =
          renderFailureSummary mentionDepOf pkg reason ++ "."
       ++ renderFailureExtraDetail reason
       ++ maybe "" showException (buildFailureException reason)
  
      renderFailureSummary mentionDepOf pkg reason =
          case reason of
            DownloadFailed  _ -> "Failed to download " ++ pkgstr
            UnpackFailed    _ -> "Failed to unpack "   ++ pkgstr
            ConfigureFailed _ -> "Failed to build "    ++ pkgstr
            BuildFailed     _ -> "Failed to build "    ++ pkgstr
            ReplFailed      _ -> "repl failed for "    ++ pkgstr
            HaddocksFailed  _ -> "Failed to build documentation for " ++ pkgstr
            TestsFailed     _ -> "Tests failed for " ++ pkgstr
            BenchFailed     _ -> "Benchmarks failed for " ++ pkgstr
            InstallFailed   _ -> "Failed to build "  ++ pkgstr
            DependentFailed depid
                              -> "Failed to build " ++ display (packageId pkg)
                              ++ " because it depends on " ++ display depid
                              ++ " which itself failed to build"
        where
          pkgstr = elabConfiguredName verbosity pkg
                ++ if mentionDepOf
                     then renderDependencyOf (installedUnitId pkg)
                     else ""
  
      renderFailureExtraDetail reason =
        case reason of
          ConfigureFailed _ -> " The failure occurred during the configure step."
          InstallFailed   _ -> " The failure occurred during the final install step."
          _                 -> ""
  
      renderDependencyOf pkgid =
        case ultimateDeps pkgid of
          []         -> ""
          (p1:[])    -> " (which is required by " ++ elabPlanPackageName verbosity p1 ++ ")"
          (p1:p2:[]) -> " (which is required by " ++ elabPlanPackageName verbosity p1
                                       ++ " and " ++ elabPlanPackageName verbosity p2 ++ ")"
          (p1:p2:_)  -> " (which is required by " ++ elabPlanPackageName verbosity p1
                                          ++ ", " ++ elabPlanPackageName verbosity p2
                                          ++ " and others)"
  
      showException e = case fromException e of
        Just (ExitFailure 1) -> ""
  
  #ifdef MIN_VERSION_unix
        -- Note [Positive "signal" exit code]
        -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        -- What's the business with the test for negative and positive
        -- signal values?  The API for process specifies that if the
        -- process died due to a signal, it returns a *negative* exit
        -- code.  So that's the negative test.
        --
        -- What about the positive test?  Well, when we find out that
        -- a process died due to a signal, we ourselves exit with that
        -- exit code.  However, we don't "kill ourselves" with the
        -- signal; we just exit with the same code as the signal: thus
        -- the caller sees a *positive* exit code.  So that's what
        -- happens when we get a positive exit code.
        Just (ExitFailure n)
          | -n == fromIntegral sigSEGV ->
              " The build process segfaulted (i.e. SIGSEGV)."
  
          |  n == fromIntegral sigSEGV ->
              " The build process terminated with exit code " ++ show n
           ++ " which may be because some part of it segfaulted. (i.e. SIGSEGV)."
  
          | -n == fromIntegral sigKILL ->
              " The build process was killed (i.e. SIGKILL). " ++ explanation
  
          |  n == fromIntegral sigKILL ->
              " The build process terminated with exit code " ++ show n
           ++ " which may be because some part of it was killed "
           ++ "(i.e. SIGKILL). " ++ explanation
          where
            explanation = "The typical reason for this is that there is not "
                       ++ "enough memory available (e.g. the OS killed a process "
                       ++ "using lots of memory)."
  #endif
        Just (ExitFailure n) ->
          " The build process terminated with exit code " ++ show n
  
        _ -> " The exception was:\n  "
  #if MIN_VERSION_base(4,8,0)
               ++ displayException e
  #else
               ++ show e
  #endif
  
      buildFailureException reason =
        case reason of
          DownloadFailed  e -> Just e
          UnpackFailed    e -> Just e
          ConfigureFailed e -> Just e
          BuildFailed     e -> Just e
          ReplFailed      e -> Just e
          HaddocksFailed  e -> Just e
          TestsFailed     e -> Just e
          BenchFailed     e -> Just e
          InstallFailed   e -> Just e
          DependentFailed _ -> Nothing
  
  data BuildFailurePresentation =
         ShowBuildSummaryOnly   BuildFailureReason
       | ShowBuildSummaryAndLog BuildFailureReason FilePath
  
  
  cmdCommonHelpTextNewBuildBeta :: String
  cmdCommonHelpTextNewBuildBeta = ""
   --    "Note: this command is part of the new project-based system (aka "
   -- ++ "nix-style\nlocal builds). These features are currently in beta. "
   -- ++ "Please see\n"
   -- ++ "http://cabal.readthedocs.io/en/latest/nix-local-build-overview.html "
   -- ++ "for\ndetails and advice on what you can expect to work. If you "
   -- ++ "encounter problems\nplease file issues at "
   -- ++ "https://github.com/haskell/cabal/issues and if you\nhave any time "
   -- ++ "to get involved and help with testing, fixing bugs etc then\nthat "
   -- ++ "is very much appreciated.\n"
  