content: %
  % (c) The University of Glasgow, 2006
  %
  \begin{code}
  {-# LANGUAGE CPP #-}
  -- | Package manipulation
  module Gen2.GHC.Packages (
          module PackageConfig,
  
          -- * The PackageConfigMap
          PackageConfigMap, emptyPackageConfigMap, lookupPackage,
          extendPackageConfigMap, dumpPackages,
  
          -- * Reading the package config, and processing cmdline args
          PackageState(..),
          initPackages,
          getPackageDetails,
          lookupModuleInAllPackages, lookupModuleWithSuggestions,
  
          -- * Inspecting the set of packages in scope
          getPackageIncludePath,
          getPackageLibraryPath,
          getPackageLinkOpts,
          getPackageExtraCcOpts,
          getPackageFrameworkPath,
          getPackageFrameworks,
          getPreloadPackagesAnd,
  
          collectIncludeDirs, collectLibraryPaths, collectLinkOpts,
          packageHsLibs,
  
          -- * Utils
          isDllName
      )
  where
  
  #include "HsVersions.h"
  
  import PackageConfig
  import DynFlags
  import Config           ( cProjectVersion )
  import Name             ( Name, nameModule_maybe )
  import UniqFM
  import Module
  import Util
  import Panic
  import Outputable
  import Maybes
  
  import Distribution.InstalledPackageInfo
  import Distribution.InstalledPackageInfo.Binary
  import Distribution.Package hiding (PackageId,depends)
  import FastString
  import ErrUtils         ( debugTraceMsg, putMsg, MsgDoc )
  import Exception
  
  import System.Directory
  import System.FilePath as FilePath
  import qualified System.FilePath.Posix as FilePath.Posix
  import Control.Monad
  import Data.Char (isSpace)
  import Data.List as List
  import Data.Map (Map)
  import qualified Data.Map as Map
  import qualified FiniteMap as Map
  import qualified Data.Set as Set
  
  import Packages (PackageState(..))
  import qualified Paths_ghcjs  as Paths
  import           System.Info  (arch, os)
  import qualified Data.Version as Version
  
  -- ---------------------------------------------------------------------------
  -- The Package state
  
  -- | Package state is all stored in 'DynFlags', including the details of
  -- all packages, which packages are exposed, and which modules they
  -- provide.
  --
  -- The package state is computed by 'initPackages', and kept in DynFlags.
  --
  --   * @-package <pkg>@ causes @<pkg>@ to become exposed, and all other packages
  --      with the same name to become hidden.
  --
  --   * @-hide-package <pkg>@ causes @<pkg>@ to become hidden.
  --
  --   * Let @exposedPackages@ be the set of packages thus exposed.
  --     Let @depExposedPackages@ be the transitive closure from @exposedPackages@ of
  --     their dependencies.
  --
  --   * When searching for a module from an preload import declaration,
  --     only the exposed modules in @exposedPackages@ are valid.
  --
  --   * When searching for a module from an implicit import, all modules
  --     from @depExposedPackages@ are valid.
  --
  --   * When linking in a compilation manager mode, we link in packages the
  --     program depends on (the compiler knows this list by the
  --     time it gets to the link step).  Also, we link in all packages
  --     which were mentioned with preload @-package@ flags on the command-line,
  --     or are a transitive dependency of same, or are \"base\"\/\"rts\".
  --     The reason for this is that we might need packages which don't
  --     contain any Haskell modules, and therefore won't be discovered
  --     by the normal mechanism of dependency tracking.
  
  -- Notes on DLLs
  -- ~~~~~~~~~~~~~
  -- When compiling module A, which imports module B, we need to
  -- know whether B will be in the same DLL as A.
  --      If it's in the same DLL, we refer to B_f_closure
  --      If it isn't, we refer to _imp__B_f_closure
  -- When compiling A, we record in B's Module value whether it's
  -- in a different DLL, by setting the DLL flag.
  {-
  data PackageState = PackageState {
    pkgIdMap              :: PackageConfigMap, -- PackageId   -> PackageConfig
          -- The exposed flags are adjusted according to -package and
          -- -hide-package flags, and -ignore-package removes packages.
  
    preloadPackages      :: [PackageId],
          -- The packages we're going to link in eagerly.  This list
          -- should be in reverse dependency order; that is, a package
          -- is always mentioned before the packages it depends on.
  
    moduleToPkgConfAll    :: UniqFM [(PackageConfig,Bool)], -- ModuleEnv mapping
          -- Derived from pkgIdMap.
          -- Maps Module to (pkgconf,exposed), where pkgconf is the
          -- PackageConfig for the package containing the module, and
          -- exposed is True if the package exposes that module.
  
    installedPackageIdMap :: InstalledPackageIdMap
    }
  -}
  -- | A PackageConfigMap maps a 'PackageId' to a 'PackageConfig'
  type PackageConfigMap = UniqFM PackageConfig
  
  -- type InstalledPackageIdMap = Map InstalledPackageId PackageId
  
  type InstalledPackageIndex = Map InstalledPackageId PackageConfig
  
  emptyPackageConfigMap :: PackageConfigMap
  emptyPackageConfigMap = emptyUFM
  
  -- | Find the package we know about with the given id (e.g. \"foo-1.0\"), if any
  lookupPackage :: PackageConfigMap -> PackageId -> Maybe PackageConfig
  lookupPackage = lookupUFM
  
  extendPackageConfigMap
     :: PackageConfigMap -> [PackageConfig] -> PackageConfigMap
  extendPackageConfigMap pkg_map new_pkgs
    = foldl add pkg_map new_pkgs
    where add pkg_map p = addToUFM pkg_map (packageConfigId p) p
  
  -- | Looks up the package with the given id in the package state, panicing if it is
  -- not found
  getPackageDetails :: PackageState -> PackageId -> PackageConfig
  getPackageDetails ps pid = expectJust "getPackageDetails" (lookupPackage (pkgIdMap ps) pid)
  
  -- ----------------------------------------------------------------------------
  -- Loading the package db files and building up the package state
  
  -- | Call this after 'DynFlags.parseDynFlags'.  It reads the package
  -- database files, and sets up various internal tables of package
  -- information, according to the package-related flags on the
  -- command-line (@-package@, @-hide-package@ etc.)
  --
  -- Returns a list of packages to link in if we're doing dynamic linking.
  -- This list contains the packages that the user explicitly mentioned with
  -- @-package@ flags.
  --
  -- 'initPackages' can be called again subsequently after updating the
  -- 'packageFlags' field of the 'DynFlags', and it will update the
  -- 'pkgState' in 'DynFlags' and return a list of packages to
  -- link in.
  initPackages :: DynFlags -> IO (DynFlags, [PackageId])
  initPackages dflags = do
    pkg_db <- case pkgDatabase dflags of
                  Nothing -> readPackageConfigs dflags
                  Just db -> return $ setBatchPackageFlags dflags db
    (pkg_state, preload, this_pkg)
          <- mkPackageState dflags pkg_db [] (thisPackage dflags)
    return (dflags{ pkgDatabase = Just pkg_db,
                    pkgState = pkg_state,
                    thisPackage = this_pkg },
            preload)
  
  -- -----------------------------------------------------------------------------
  -- Reading the package database(s)
  
  readPackageConfigs :: DynFlags -> IO [PackageConfig]
  readPackageConfigs dflags = do
    let system_conf_refs = [UserPkgConf, GlobalPkgConf]
  
    -- incompatible with Cabal
    -- e_pkg_path <- tryIO (getEnv "GHCJS_PACKAGE_PATH")
    let e_pkg_path = Left ""
    let base_conf_refs = case e_pkg_path of
          Left _ -> system_conf_refs
          Right path
           | null (last cs)
           -> map PkgConfFile (init cs) ++ system_conf_refs
           | otherwise
           -> map PkgConfFile cs
           where cs = parseSearchPath path
           -- if the path ends in a separator (eg. "/foo/bar:")
           -- then we tack on the system paths.
  
    let conf_refs = reverse (extraPkgConfs dflags base_conf_refs)
    -- later packages shadow earlier ones.  extraPkgConfs
    -- is in the opposite order to the flags on the
    -- command line.
    confs <- liftM catMaybes $ mapM (resolvePackageConfig dflags) conf_refs
  
    liftM concat $ mapM (readPackageConfig dflags) confs
  
  resolvePackageConfig :: DynFlags -> PkgConfRef -> IO (Maybe FilePath)
  resolvePackageConfig dflags GlobalPkgConf = return $ Just (systemPackageConfig dflags)
  resolvePackageConfig _ UserPkgConf = handleIO (\_ -> return Nothing) $ do
    appdir <- getAppUserDataDirectory "ghcjs"
    let dir = appdir </> (arch ++ '-': os ++ '-':Version.showVersion Paths.version ++ '-':cProjectVersion)
        pkgconf = dir </> "package.conf.d"
    exist <- doesDirectoryExist pkgconf
    return $ if exist then Just pkgconf else Nothing
  resolvePackageConfig _ (PkgConfFile name) = return $ Just name
  
  readPackageConfig :: DynFlags -> FilePath -> IO [PackageConfig]
  readPackageConfig dflags conf_file = do
    isdir <- doesDirectoryExist conf_file
  
    proto_pkg_configs <-
      if isdir
         then do let filename = conf_file </> "package.cache"
                 debugTraceMsg dflags 2 (text "Using binary package database:" <+> text filename)
                 conf <- readBinPackageDB filename
                 return (map installedPackageInfoToPackageConfig conf)
  
         else do
              isfile <- doesFileExist conf_file
              when (not isfile) $
                throwGhcExceptionIO $ InstallationError $
                  "can't find a package database at " ++ conf_file
              debugTraceMsg dflags 2 (text "Using package config file:" <+> text conf_file)
              str <- readFile conf_file
              case reads str of
                  [(configs, rest)]
                      | all isSpace rest -> return (map installedPackageInfoToPackageConfig configs)
                  _ -> throwGhcExceptionIO $ InstallationError $
                          "invalid package database file " ++ conf_file
  
    let
        top_dir = topDir dflags
        pkgroot = takeDirectory conf_file
        pkg_configs1 = map (mungePackagePaths top_dir pkgroot) proto_pkg_configs
        pkg_configs2 = setBatchPackageFlags dflags pkg_configs1
    --
    return pkg_configs2
  
  setBatchPackageFlags :: DynFlags -> [PackageConfig] -> [PackageConfig]
  setBatchPackageFlags dflags pkgs = (maybeDistrustAll . maybeHideAll) pkgs
    where
      maybeHideAll pkgs'
        | gopt Opt_HideAllPackages dflags = map hide pkgs'
        | otherwise                       = pkgs'
  
      maybeDistrustAll pkgs'
        | gopt Opt_DistrustAllPackages dflags = map distrust pkgs'
        | otherwise                           = pkgs'
  
      hide pkg = pkg{ exposed = False }
      distrust pkg = pkg{ trusted = False }
  
  -- TODO: This code is duplicated in utils/ghc-pkg/Main.hs
  mungePackagePaths :: FilePath -> FilePath -> PackageConfig -> PackageConfig
  -- Perform path/URL variable substitution as per the Cabal ${pkgroot} spec
  -- (http://www.haskell.org/pipermail/libraries/2009-May/011772.html)
  -- Paths/URLs can be relative to ${pkgroot} or ${pkgrooturl}.
  -- The "pkgroot" is the directory containing the package database.
  --
  -- Also perform a similar substitution for the older GHC-specific
  -- "$topdir" variable. The "topdir" is the location of the ghc
  -- installation (obtained from the -B option).
  mungePackagePaths top_dir pkgroot pkg =
      pkg {
        importDirs  = munge_paths (importDirs pkg),
        includeDirs = munge_paths (includeDirs pkg),
        libraryDirs = munge_paths (libraryDirs pkg),
        frameworkDirs = munge_paths (frameworkDirs pkg),
        haddockInterfaces = munge_paths (haddockInterfaces pkg),
        haddockHTMLs = munge_urls (haddockHTMLs pkg)
      }
    where
      munge_paths = map munge_path
      munge_urls  = map munge_url
  
      munge_path p
        | Just p' <- stripVarPrefix "${pkgroot}" p = pkgroot ++ p'
        | Just p' <- stripVarPrefix "$topdir"    p = top_dir ++ p'
        | otherwise                                = p
  
      munge_url p
        | Just p' <- stripVarPrefix "${pkgrooturl}" p = toUrlPath pkgroot p'
        | Just p' <- stripVarPrefix "$httptopdir"   p = toUrlPath top_dir p'
        | otherwise                                   = p
  
      toUrlPath r p = "file:///"
                   -- URLs always use posix style '/' separators:
                   ++ FilePath.Posix.joinPath
                          (r : -- We need to drop a leading "/" or "\\"
                               -- if there is one:
                               dropWhile (all isPathSeparator)
                                         (FilePath.splitDirectories p))
  
      -- We could drop the separator here, and then use </> above. However,
      -- by leaving it in and using ++ we keep the same path separator
      -- rather than letting FilePath change it to use \ as the separator
      stripVarPrefix var path = case stripPrefix var path of
                                Just [] -> Just []
                                Just cs@(c : _) | isPathSeparator c -> Just cs
                                _ -> Nothing
  
  
  -- -----------------------------------------------------------------------------
  -- Modify our copy of the package database based on a package flag
  -- (-package, -hide-package, -ignore-package).
  
  applyPackageFlag
     :: DynFlags
     -> UnusablePackages
     -> [PackageConfig]           -- Initial database
     -> PackageFlag               -- flag to apply
     -> IO [PackageConfig]        -- new database
  
  applyPackageFlag dflags unusable pkgs flag =
    case flag of
      ExposePackage str ->
         case selectPackages (matchingStr str) pkgs unusable of
           Left ps         -> packageFlagErr dflags flag ps
           Right (p:ps,qs) -> return (p':ps')
            where p' = p {exposed=True}
                  ps' = hideAll (pkgName (sourcePackageId p)) (ps++qs)
           _ -> panic "applyPackageFlag"
  
      ExposePackageId str ->
         case selectPackages (matchingId str) pkgs unusable of
           Left ps         -> packageFlagErr dflags flag ps
           Right (p:ps,qs) -> return (p':ps')
            where p' = p {exposed=True}
                  ps' = hideAll (pkgName (sourcePackageId p)) (ps++qs)
           _ -> panic "applyPackageFlag"
  
      HidePackage str ->
         case selectPackages (matchingStr str) pkgs unusable of
           Left ps       -> packageFlagErr dflags flag ps
           Right (ps,qs) -> return (map hide ps ++ qs)
            where hide p = p {exposed=False}
  
      -- we trust all matching packages. Maybe should only trust first one?
      -- and leave others the same or set them untrusted
      TrustPackage str ->
         case selectPackages (matchingStr str) pkgs unusable of
           Left ps       -> packageFlagErr dflags flag ps
           Right (ps,qs) -> return (map trust ps ++ qs)
            where trust p = p {trusted=True}
  
      DistrustPackage str ->
         case selectPackages (matchingStr str) pkgs unusable of
           Left ps       -> packageFlagErr dflags flag ps
           Right (ps,qs) -> return (map distrust ps ++ qs)
            where distrust p = p {trusted=False}
  
      _ -> panic "applyPackageFlag"
  
     where
          -- When a package is requested to be exposed, we hide all other
          -- packages with the same name.
          hideAll name ps = map maybe_hide ps
            where maybe_hide p
                     | pkgName (sourcePackageId p) == name = p {exposed=False}
                     | otherwise                           = p
  
  
  selectPackages :: (PackageConfig -> Bool) -> [PackageConfig]
                 -> UnusablePackages
                 -> Either [(PackageConfig, UnusablePackageReason)]
                    ([PackageConfig], [PackageConfig])
  selectPackages matches pkgs unusable
    = let
          (ps,rest) = partition matches pkgs
          reasons = [ (p, Map.lookup (installedPackageId p) unusable)
                    | p <- ps ]
      in
      if all (isJust.snd) reasons
         then Left  [ (p, reason) | (p,Just reason) <- reasons ]
         else Right (sortByVersion [ p | (p,Nothing) <- reasons ], rest)
  
  -- A package named on the command line can either include the
  -- version, or just the name if it is unambiguous.
  matchingStr :: String -> PackageConfig -> Bool
  matchingStr str p
          =  str == display (sourcePackageId p)
          || str == display (pkgName (sourcePackageId p))
  
  matchingId :: String -> PackageConfig -> Bool
  matchingId str p =  InstalledPackageId str == installedPackageId p
  
  sortByVersion :: [InstalledPackageInfo_ m] -> [InstalledPackageInfo_ m]
  sortByVersion = sortBy (flip (comparing (pkgVersion.sourcePackageId)))
  
  comparing :: Ord a => (t -> a) -> t -> t -> Ordering
  comparing f a b = f a `compare` f b
  
  packageFlagErr :: DynFlags
                 -> PackageFlag
                 -> [(PackageConfig, UnusablePackageReason)]
                 -> IO a
  
  -- for missing DPH package we emit a more helpful error message, because
  -- this may be the result of using -fdph-par or -fdph-seq.
  packageFlagErr dflags (ExposePackage pkg) [] | is_dph_package pkg
    = throwGhcExceptionIO (CmdLineError (showSDoc dflags $ dph_err))
    where dph_err = text "the " <> text pkg <> text " package is not installed."
                    $$ text "To install it: \"cabal install dph\"."
          is_dph_package pkg = "dph" `isPrefixOf` pkg
  
  packageFlagErr dflags flag reasons
    = throwGhcExceptionIO (CmdLineError (showSDoc dflags $ err))
    where err = text "cannot satisfy " <> ppr_flag <>
                  (if null reasons then empty else text ": ") $$
                nest 4 (ppr_reasons $$
                        text "(use -v for more information)")
          ppr_flag = case flag of
                       IgnorePackage p -> text "-ignore-package " <> text p
                       HidePackage p   -> text "-hide-package " <> text p
                       ExposePackage p -> text "-package " <> text p
                       ExposePackageId p -> text "-package-id " <> text p
                       TrustPackage p    -> text "-trust " <> text p
                       DistrustPackage p -> text "-distrust " <> text p
          ppr_reasons = vcat (map ppr_reason reasons)
          ppr_reason (p, reason) = pprReason (pprIPkg p <+> text "is") reason
  
  -- -----------------------------------------------------------------------------
  -- Hide old versions of packages
  
  --
  -- hide all packages for which there is also a later version
  -- that is already exposed.  This just makes it non-fatal to have two
  -- versions of a package exposed, which can happen if you install a
  -- later version of a package in the user database, for example.
  --
  hideOldPackages :: DynFlags -> [PackageConfig] -> IO [PackageConfig]
  hideOldPackages dflags pkgs = mapM maybe_hide pkgs
    where maybe_hide p
             | not (exposed p) = return p
             | (p' : _) <- later_versions = do
                  debugTraceMsg dflags 2 $
                     (ptext (sLit "hiding package") <+> pprSPkg p <+>
                      ptext (sLit "to avoid conflict with later version") <+>
                      pprSPkg p')
                  return (p {exposed=False})
             | otherwise = return p
            where myname = pkgName (sourcePackageId p)
                  myversion = pkgVersion (sourcePackageId p)
                  later_versions = [ p | p <- pkgs, exposed p,
                                         let pkg = sourcePackageId p,
                                         pkgName pkg == myname,
                                         pkgVersion pkg > myversion ]
  
  -- -----------------------------------------------------------------------------
  -- Wired-in packages
  
  findWiredInPackages
     :: DynFlags
     -> [PackageConfig]           -- database
     -> IO [PackageConfig]
  
  findWiredInPackages dflags pkgs = do
    --
    -- Now we must find our wired-in packages, and rename them to
    -- their canonical names (eg. base-1.0 ==> base).
    --
    let
          wired_in_pkgids :: [String]
          wired_in_pkgids = map packageIdString
                            [ primPackageId,
                              integerPackageId,
                              basePackageId,
                              rtsPackageId,
                              thPackageId,
                              dphSeqPackageId,
                              dphParPackageId ]
  
          matches :: PackageConfig -> String -> Bool
          pc `matches` pid = display (pkgName (sourcePackageId pc)) == pid
  
          -- find which package corresponds to each wired-in package
          -- delete any other packages with the same name
          -- update the package and any dependencies to point to the new
          -- one.
          --
          -- When choosing which package to map to a wired-in package
          -- name, we prefer exposed packages, and pick the latest
          -- version.  To override the default choice, -hide-package
          -- could be used to hide newer versions.
          --
          findWiredInPackage :: [PackageConfig] -> String
                             -> IO (Maybe InstalledPackageId)
          findWiredInPackage pkgs wired_pkg =
             let all_ps = [ p | p <- pkgs, p `matches` wired_pkg ] in
             case all_ps of
                  []   -> notfound
                  many -> pick (head (sortByVersion many))
            where
                  notfound = do
                            debugTraceMsg dflags 2 $
                              ptext (sLit "wired-in package ")
                                   <> text wired_pkg
                                   <> ptext (sLit " not found.")
                            return Nothing
                  pick :: InstalledPackageInfo_ ModuleName
                       -> IO (Maybe InstalledPackageId)
                  pick pkg = do
                          debugTraceMsg dflags 2 $
                              ptext (sLit "wired-in package ")
                                   <> text wired_pkg
                                   <> ptext (sLit " mapped to ")
                                   <> pprIPkg pkg
                          return (Just (installedPackageId pkg))
  
  
    mb_wired_in_ids <- mapM (findWiredInPackage pkgs) wired_in_pkgids
    let
          wired_in_ids = catMaybes mb_wired_in_ids
  
          -- this is old: we used to assume that if there were
          -- multiple versions of wired-in packages installed that
          -- they were mutually exclusive.  Now we're assuming that
          -- you have one "main" version of each wired-in package
          -- (the latest version), and the others are backward-compat
          -- wrappers that depend on this one.  e.g. base-4.0 is the
          -- latest, base-3.0 is a compat wrapper depending on base-4.0.
          {-
          deleteOtherWiredInPackages pkgs = filterOut bad pkgs
            where bad p = any (p `matches`) wired_in_pkgids
                        && package p `notElem` map fst wired_in_ids
          -}
  
          updateWiredInDependencies pkgs = map upd_pkg pkgs
            where upd_pkg p
                    | installedPackageId p `elem` wired_in_ids
                    = p { sourcePackageId = (sourcePackageId p){ pkgVersion = Version [] [] } }
                    | otherwise
                    = p
  
    return $ updateWiredInDependencies pkgs
  
  -- ----------------------------------------------------------------------------
  
  data UnusablePackageReason
    = IgnoredWithFlag
    | MissingDependencies [InstalledPackageId]
    | ShadowedBy InstalledPackageId
  
  type UnusablePackages = Map InstalledPackageId UnusablePackageReason
  
  pprReason :: SDoc -> UnusablePackageReason -> SDoc
  pprReason pref reason = case reason of
    IgnoredWithFlag ->
        pref <+> ptext (sLit "ignored due to an -ignore-package flag")
    MissingDependencies deps ->
        pref <+>
        ptext (sLit "unusable due to missing or recursive dependencies:") $$
          nest 2 (hsep (map (text.display) deps))
    ShadowedBy ipid ->
        pref <+> ptext (sLit "shadowed by package ") <> text (display ipid)
  
  reportUnusable :: DynFlags -> UnusablePackages -> IO ()
  reportUnusable dflags pkgs = mapM_ report (Map.toList pkgs)
    where
      report (ipid, reason) =
         debugTraceMsg dflags 2 $
           pprReason
             (ptext (sLit "package") <+>
              text (display ipid) <+> text "is") reason
  
  -- ----------------------------------------------------------------------------
  --
  -- Detect any packages that have missing dependencies, and also any
  -- mutually-recursive groups of packages (loops in the package graph
  -- are not allowed).  We do this by taking the least fixpoint of the
  -- dependency graph, repeatedly adding packages whose dependencies are
  -- satisfied until no more can be added.
  --
  findBroken :: [PackageConfig] -> UnusablePackages
  findBroken pkgs = go [] Map.empty pkgs
   where
     go avail ipids not_avail =
       case partitionWith (depsAvailable ipids) not_avail of
          ([], not_avail) ->
              Map.fromList [ (installedPackageId p, MissingDependencies deps)
                           | (p,deps) <- not_avail ]
          (new_avail, not_avail) ->
              go (new_avail ++ avail) new_ipids (map fst not_avail)
              where new_ipids = Map.insertList
                                  [ (installedPackageId p, p) | p <- new_avail ]
                                  ipids
  
     depsAvailable :: InstalledPackageIndex
                   -> PackageConfig
                   -> Either PackageConfig (PackageConfig, [InstalledPackageId])
     depsAvailable ipids pkg
          | null dangling = Left pkg
          | otherwise     = Right (pkg, dangling)
          where dangling = filter (not . (`Map.member` ipids)) (depends pkg)
  
  -- -----------------------------------------------------------------------------
  -- Eliminate shadowed packages, giving the user some feedback
  
  -- later packages in the list should shadow earlier ones with the same
  -- package name/version.  Additionally, a package may be preferred if
  -- it is in the transitive closure of packages selected using -package-id
  -- flags.
  shadowPackages :: [PackageConfig] -> [InstalledPackageId] -> UnusablePackages
  shadowPackages pkgs preferred
   = let (shadowed,_) = foldl check ([],emptyUFM) pkgs
     in  Map.fromList shadowed
   where
   check (shadowed,pkgmap) pkg
        | Just oldpkg <- lookupUFM pkgmap (packageConfigId pkg)
        , let
              ipid_new = installedPackageId pkg
              ipid_old = installedPackageId oldpkg
          --
        , ipid_old /= ipid_new
        = if ipid_old `elem` preferred
             then ( (ipid_new, ShadowedBy ipid_old) : shadowed, pkgmap )
             else ( (ipid_old, ShadowedBy ipid_new) : shadowed, pkgmap' )
        | otherwise
        = (shadowed, pkgmap')
        where
          pkgmap' = addToUFM pkgmap (packageConfigId pkg) pkg
  
  -- -----------------------------------------------------------------------------
  
  ignorePackages :: [PackageFlag] -> [PackageConfig] -> UnusablePackages
  ignorePackages flags pkgs = Map.fromList (concatMap doit flags)
    where
    doit (IgnorePackage str) =
       case partition (matchingStr str) pkgs of
           (ps, _) -> [ (installedPackageId p, IgnoredWithFlag)
                      | p <- ps ]
          -- missing package is not an error for -ignore-package,
          -- because a common usage is to -ignore-package P as
          -- a preventative measure just in case P exists.
    doit _ = panic "ignorePackages"
  
  -- -----------------------------------------------------------------------------
  
  depClosure :: InstalledPackageIndex
             -> [InstalledPackageId]
             -> [InstalledPackageId]
  depClosure index ipids = closure Map.empty ipids
    where
     closure set [] = Map.keys set
     closure set (ipid : ipids)
       | ipid `Map.member` set = closure set ipids
       | Just p <- Map.lookup ipid index = closure (Map.insert ipid p set)
                                                   (depends p ++ ipids)
       | otherwise = closure set ipids
  
  -- -----------------------------------------------------------------------------
  -- When all the command-line options are in, we can process our package
  -- settings and populate the package state.
  
  mkPackageState
      :: DynFlags
      -> [PackageConfig]          -- initial database
      -> [PackageId]              -- preloaded packages
      -> PackageId                -- this package
      -> IO (PackageState,
             [PackageId],         -- new packages to preload
             PackageId) -- this package, might be modified if the current
                        -- package is a wired-in package.
  
  mkPackageState dflags pkgs0 preload0 this_package = do
  
  {-
     Plan.
  
     1. P = transitive closure of packages selected by -package-id
  
     2. Apply shadowing.  When there are multiple packages with the same
        sourcePackageId,
          * if one is in P, use that one
          * otherwise, use the one highest in the package stack
        [
         rationale: we cannot use two packages with the same sourcePackageId
         in the same program, because sourcePackageId is the symbol prefix.
         Hence we must select a consistent set of packages to use.  We have
         a default algorithm for doing this: packages higher in the stack
         shadow those lower down.  This default algorithm can be overriden
         by giving explicit -package-id flags; then we have to take these
         preferences into account when selecting which other packages are
         made available.
  
         Our simple algorithm throws away some solutions: there may be other
         consistent sets that would satisfy the -package flags, but it's
         not GHC's job to be doing constraint solving.
        ]
  
     3. remove packages selected by -ignore-package
  
     4. remove any packages with missing dependencies, or mutually recursive
        dependencies.
  
     5. report (with -v) any packages that were removed by steps 2-4
  
     6. apply flags to set exposed/hidden on the resulting packages
        - if any flag refers to a package which was removed by 2-4, then
          we can give an error message explaining why
  
     7. hide any packages which are superseded by later exposed packages
  -}
  
    let
        flags = reverse (packageFlags dflags)
  
        -- pkgs0 with duplicate packages filtered out.  This is
        -- important: it is possible for a package in the global package
        -- DB to have the same IPID as a package in the user DB, and
        -- we want the latter to take precedence.  This is not the same
        -- as shadowing (below), since in this case the two packages
        -- have the same ABI and are interchangeable.
        --
        -- #4072: note that we must retain the ordering of the list here
        -- so that shadowing behaves as expected when we apply it later.
        pkgs0_unique = snd $ foldr del (Set.empty,[]) pkgs0
            where del p (s,ps)
                    | pid `Set.member` s = (s,ps)
                    | otherwise          = (Set.insert pid s, p:ps)
                    where pid = installedPackageId p
            -- XXX this is just a variant of nub
  
        ipid_map = Map.fromList [ (installedPackageId p, p) | p <- pkgs0 ]
  
        ipid_selected = depClosure ipid_map [ InstalledPackageId i
                                            | ExposePackageId i <- flags ]
  
        (ignore_flags, other_flags) = partition is_ignore flags
        is_ignore IgnorePackage{} = True
        is_ignore _ = False
  
        shadowed = shadowPackages pkgs0_unique ipid_selected
  
        ignored  = ignorePackages ignore_flags pkgs0_unique
  
        pkgs0' = filter (not . (`Map.member` (Map.union shadowed ignored)) . installedPackageId) pkgs0_unique
        broken   = findBroken pkgs0'
        unusable = shadowed `Map.union` ignored `Map.union` broken
  
    reportUnusable dflags unusable
  
    --
    -- Modify the package database according to the command-line flags
    -- (-package, -hide-package, -ignore-package, -hide-all-packages).
    --
    pkgs1 <- foldM (applyPackageFlag dflags unusable) pkgs0_unique other_flags
    let pkgs2 = filter (not . (`Map.member` unusable) . installedPackageId) pkgs1
  
    -- Here we build up a set of the packages mentioned in -package
    -- flags on the command line; these are called the "preload"
    -- packages.  we link these packages in eagerly.  The preload set
    -- should contain at least rts & base, which is why we pretend that
    -- the command line contains -package rts & -package base.
    --
    let preload1 = [ installedPackageId p | f <- flags, p <- get_exposed f ]
  
        get_exposed (ExposePackage   s)
           = take 1 $ sortByVersion (filter (matchingStr s) pkgs2)
           --  -package P means "the latest version of P" (#7030)
        get_exposed (ExposePackageId s) = filter (matchingId  s) pkgs2
        get_exposed _                   = []
  
    -- hide packages that are subsumed by later versions
    pkgs3 <- hideOldPackages dflags pkgs2
  
    -- sort out which packages are wired in
    pkgs4 <- findWiredInPackages dflags pkgs3
  
    let pkg_db = extendPackageConfigMap emptyPackageConfigMap pkgs4
  
        ipid_map = Map.fromList [ (installedPackageId p, packageConfigId p)
                                | p <- pkgs4 ]
  
        lookupIPID ipid@(InstalledPackageId str)
           | Just pid <- Map.lookup ipid ipid_map = return pid
           | otherwise                            = missingPackageErr dflags str
  
    preload2 <- mapM lookupIPID preload1
  
    let
        -- add base & rts to the preload packages
        basicLinkedPackages
         | gopt Opt_AutoLinkPackages dflags
            = filter (flip elemUFM pkg_db) [basePackageId, rtsPackageId]
         | otherwise = []
        -- but in any case remove the current package from the set of
        -- preloaded packages so that base/rts does not end up in the
        -- set up preloaded package when we are just building it
        preload3 = nub $ filter (/= this_package)
                       $ (basicLinkedPackages ++ preload2)
  
    -- Close the preload packages with their dependencies
    dep_preload <- closeDeps dflags pkg_db ipid_map (zip preload3 (repeat Nothing))
    let new_dep_preload = filter (`notElem` preload0) dep_preload
  
    let pstate = PackageState{ preloadPackages     = dep_preload,
                               pkgIdMap            = pkg_db,
                               moduleToPkgConfAll  = mkModuleMap pkg_db,
                               installedPackageIdMap = ipid_map
                             }
  
    return (pstate, new_dep_preload, this_package)
  
  
  -- -----------------------------------------------------------------------------
  -- Make the mapping from module to package info
  
  mkModuleMap
    :: PackageConfigMap
    -> UniqFM [(PackageConfig, Bool)]
  mkModuleMap pkg_db = foldr extend_modmap emptyUFM pkgids
    where
          pkgids = map packageConfigId (eltsUFM pkg_db)
  
          extend_modmap pkgid modmap =
                  addListToUFM_C (++) modmap
                     ([(m, [(pkg, True)])  | m <- exposed_mods] ++
                      [(m, [(pkg, False)]) | m <- hidden_mods])
            where
                  pkg = expectJust "mkModuleMap" (lookupPackage pkg_db pkgid)
                  exposed_mods = exposedModules pkg
                  hidden_mods  = hiddenModules pkg
  
  pprSPkg :: PackageConfig -> SDoc
  pprSPkg p = text (display (sourcePackageId p))
  
  pprIPkg :: PackageConfig -> SDoc
  pprIPkg p = text (display (installedPackageId p))
  
  -- -----------------------------------------------------------------------------
  -- Extracting information from the packages in scope
  
  -- Many of these functions take a list of packages: in those cases,
  -- the list is expected to contain the "dependent packages",
  -- i.e. those packages that were found to be depended on by the
  -- current module/program.  These can be auto or non-auto packages, it
  -- doesn't really matter.  The list is always combined with the list
  -- of preload (command-line) packages to determine which packages to
  -- use.
  
  -- | Find all the include directories in these and the preload packages
  getPackageIncludePath :: DynFlags -> [PackageId] -> IO [String]
  getPackageIncludePath dflags pkgs =
    collectIncludeDirs `fmap` getPreloadPackagesAnd dflags pkgs
  
  collectIncludeDirs :: [PackageConfig] -> [FilePath]
  collectIncludeDirs ps = nub (filter notNull (concatMap includeDirs ps))
  
  -- | Find all the library paths in these and the preload packages
  getPackageLibraryPath :: DynFlags -> [PackageId] -> IO [String]
  getPackageLibraryPath dflags pkgs =
    collectLibraryPaths `fmap` getPreloadPackagesAnd dflags pkgs
  
  collectLibraryPaths :: [PackageConfig] -> [FilePath]
  collectLibraryPaths ps = nub (filter notNull (concatMap libraryDirs ps))
  
  -- | Find all the link options in these and the preload packages,
  -- returning (package hs lib options, extra library options, other flags)
  getPackageLinkOpts :: DynFlags -> [PackageId] -> IO ([String], [String], [String])
  getPackageLinkOpts dflags pkgs =
    collectLinkOpts dflags `fmap` getPreloadPackagesAnd dflags pkgs
  
  collectLinkOpts :: DynFlags -> [PackageConfig] -> ([String], [String], [String])
  collectLinkOpts dflags ps =
      (
          concatMap (map ("-l" ++) . packageHsLibs dflags) ps,
          concatMap (map ("-l" ++) . extraLibraries) ps,
          concatMap ldOptions ps
      )
  
  packageHsLibs :: DynFlags -> PackageConfig -> [String]
  packageHsLibs dflags p = map (mkDynName . addSuffix) (hsLibraries p)
    where
          ways0 = ways dflags
  
          ways1 = filter (/= WayDyn) ways0
          -- the name of a shared library is libHSfoo-ghc<version>.so
          -- we leave out the _dyn, because it is superfluous
  
          -- debug RTS includes support for -eventlog
          ways2 | WayDebug `elem` ways1
                = filter (/= WayEventLog) ways1
                | otherwise
                = ways1
  
          tag     = mkBuildTag (filter (not . wayRTSOnly) ways2)
          rts_tag = mkBuildTag ways2
  
          mkDynName x
           | gopt Opt_Static dflags       = x
           | "HS" `isPrefixOf` x          = x ++ "-ghc" ++ cProjectVersion
             -- For non-Haskell libraries, we use the name "Cfoo". The .a
             -- file is libCfoo.a, and the .so is libfoo.so. That way the
             -- linker knows what we mean for the vanilla (-lCfoo) and dyn
             -- (-lfoo) ways. We therefore need to strip the 'C' off here.
           | Just x' <- stripPrefix "C" x = x'
           | otherwise
              = panic ("Don't understand library name " ++ x)
  
          addSuffix rts@"HSrts"    = rts       ++ (expandTag rts_tag)
          addSuffix other_lib      = other_lib ++ (expandTag tag)
  
          expandTag t | null t = ""
                      | otherwise = '_':t
  
  -- | Find all the C-compiler options in these and the preload packages
  getPackageExtraCcOpts :: DynFlags -> [PackageId] -> IO [String]
  getPackageExtraCcOpts dflags pkgs = do
    ps <- getPreloadPackagesAnd dflags pkgs
    return (concatMap ccOptions ps)
  
  -- | Find all the package framework paths in these and the preload packages
  getPackageFrameworkPath  :: DynFlags -> [PackageId] -> IO [String]
  getPackageFrameworkPath dflags pkgs = do
    ps <- getPreloadPackagesAnd dflags pkgs
    return (nub (filter notNull (concatMap frameworkDirs ps)))
  
  -- | Find all the package frameworks in these and the preload packages
  getPackageFrameworks  :: DynFlags -> [PackageId] -> IO [String]
  getPackageFrameworks dflags pkgs = do
    ps <- getPreloadPackagesAnd dflags pkgs
    return (concatMap frameworks ps)
  
  -- -----------------------------------------------------------------------------
  -- Package Utils
  
  -- | Takes a 'Module', and if the module is in a package returns
  -- @(pkgconf, exposed)@ where pkgconf is the PackageConfig for that package,
  -- and exposed is @True@ if the package exposes the module.
  lookupModuleInAllPackages :: DynFlags -> ModuleName -> [(PackageConfig,Bool)]
  lookupModuleInAllPackages dflags m
    = case lookupModuleWithSuggestions dflags m of
        Right pbs -> pbs
        Left  _   -> []
  
  lookupModuleWithSuggestions
    :: DynFlags -> ModuleName
    -> Either [Module] [(PackageConfig,Bool)]
           -- Lookup module in all packages
           -- Right pbs   =>   found in pbs
           -- Left  ms    =>   not found; but here are sugestions
  lookupModuleWithSuggestions dflags m
    = case lookupUFM (moduleToPkgConfAll pkg_state) m of
          Nothing -> Left suggestions
          Just ps -> Right ps
    where
      pkg_state = pkgState dflags
      suggestions
        | gopt Opt_HelpfulErrors dflags = fuzzyLookup (moduleNameString m) all_mods
        | otherwise                     = []
  
      all_mods :: [(String, Module)]     -- All modules
      all_mods = [ (moduleNameString mod_nm, mkModule pkg_id mod_nm)
                 | pkg_config <- eltsUFM (pkgIdMap pkg_state)
                 , let pkg_id = packageConfigId pkg_config
                 , mod_nm <- exposedModules pkg_config ]
  
  -- | Find all the 'PackageConfig' in both the preload packages from 'DynFlags' and corresponding to the list of
  -- 'PackageConfig's
  getPreloadPackagesAnd :: DynFlags -> [PackageId] -> IO [PackageConfig]
  getPreloadPackagesAnd dflags pkgids =
    let
        state   = pkgState dflags
        pkg_map = pkgIdMap state
        ipid_map = installedPackageIdMap state
        preload = preloadPackages state
        pairs = zip pkgids (repeat Nothing)
    in do
    all_pkgs <- throwErr dflags (foldM (add_package pkg_map ipid_map) preload pairs)
    return (map (getPackageDetails state) all_pkgs)
  
  -- Takes a list of packages, and returns the list with dependencies included,
  -- in reverse dependency order (a package appears before those it depends on).
  closeDeps :: DynFlags
            -> PackageConfigMap
            -> Map InstalledPackageId PackageId
            -> [(PackageId, Maybe PackageId)]
            -> IO [PackageId]
  closeDeps dflags pkg_map ipid_map ps
      = throwErr dflags (closeDepsErr pkg_map ipid_map ps)
  
  throwErr :: DynFlags -> MaybeErr MsgDoc a -> IO a
  throwErr dflags m
                = case m of
                  Failed e    -> throwGhcExceptionIO (CmdLineError (showSDoc dflags e))
                  Succeeded r -> return r
  
  closeDepsErr :: PackageConfigMap
               -> Map InstalledPackageId PackageId
               -> [(PackageId,Maybe PackageId)]
               -> MaybeErr MsgDoc [PackageId]
  closeDepsErr pkg_map ipid_map ps = foldM (add_package pkg_map ipid_map) [] ps
  
  -- internal helper
  add_package :: PackageConfigMap
              -> Map InstalledPackageId PackageId
              -> [PackageId]
              -> (PackageId,Maybe PackageId)
              -> MaybeErr MsgDoc [PackageId]
  add_package pkg_db ipid_map ps (p, mb_parent)
    | p `elem` ps = return ps     -- Check if we've already added this package
    | otherwise =
        case lookupPackage pkg_db p of
          Nothing -> Failed (missingPackageMsg (packageIdString p) <>
                             missingDependencyMsg mb_parent)
          Just pkg -> do
             -- Add the package's dependents also
             ps' <- foldM add_package_ipid ps (depends pkg)
             return (p : ps')
            where
              add_package_ipid ps ipid@(InstalledPackageId str)
                | Just pid <- Map.lookup ipid ipid_map
                = add_package pkg_db ipid_map ps (pid, Just p)
                | otherwise
                = Failed (missingPackageMsg str <> missingDependencyMsg mb_parent)
  
  missingPackageErr :: DynFlags -> String -> IO a
  missingPackageErr dflags p
      = throwGhcExceptionIO (CmdLineError (showSDoc dflags (missingPackageMsg p)))
  
  missingPackageMsg :: String -> SDoc
  missingPackageMsg p = ptext (sLit "unknown package:") <+> text p
  
  missingDependencyMsg :: Maybe PackageId -> SDoc
  missingDependencyMsg Nothing = empty
  missingDependencyMsg (Just parent)
    = space <> parens (ptext (sLit "dependency of") <+> ftext (packageIdFS parent))
  
  -- -----------------------------------------------------------------------------
  
  -- | Will the 'Name' come from a dynamically linked library?
  isDllName :: DynFlags -> PackageId -> Module -> Name -> Bool
  -- Despite the "dll", I think this function just means that
  -- the synbol comes from another dynamically-linked package,
  -- and applies on all platforms, not just Windows
  isDllName dflags this_pkg this_mod name
    | gopt Opt_Static dflags = False
    | Just mod <- nameModule_maybe name
      = if modulePackageId mod /= this_pkg
        then True
        else case dllSplit dflags of
             Nothing -> False
             Just ss ->
                 let findMod m = let modStr = moduleNameString (moduleName m)
                                 in case find (modStr `Set.member`) ss of
                                    Just i -> i
                                    Nothing -> panic ("Can't find " ++ modStr ++ "in DLL split")
                 in findMod mod /= findMod this_mod
         
    | otherwise = False  -- no, it is not even an external name
  
  -- -----------------------------------------------------------------------------
  -- Displaying packages
  
  -- | Show package info on console, if verbosity is >= 3
  dumpPackages :: DynFlags -> IO ()
  dumpPackages dflags
    = do let pkg_map = pkgIdMap (pkgState dflags)
         putMsg dflags $
               vcat (map (text . showInstalledPackageInfo
                               . packageConfigToInstalledPackageInfo)
                         (eltsUFM pkg_map))
  \end{code}
  