Configure.hs

{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.Configure
-- Copyright   :  Isaac Jones 2003-2005
-- License     :  BSD3
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- This deals with the /configure/ phase. It provides the 'configure' action
-- which is given the package description and configure flags. It then tries
-- to: configure the compiler; resolves any conditionals in the package
-- description; resolve the package dependencies; check if all the extensions
-- used by this package are supported by the compiler; check that all the build
-- tools are available (including version checks if appropriate); checks for
-- any required @pkg-config@ packages (updating the 'BuildInfo' with the
-- results)
--
-- Then based on all this it saves the info in the 'LocalBuildInfo' and writes
-- it out to the @dist\/setup-config@ file. It also displays various details to
-- the user, the amount of information displayed depending on the verbosity
-- level.

module Distribution.Simple.Configure (configure,
                                      writePersistBuildConfig,
                                      getConfigStateFile,
                                      getPersistBuildConfig,
                                      checkPersistBuildConfigOutdated,
                                      tryGetPersistBuildConfig,
                                      maybeGetPersistBuildConfig,
                                      findDistPref, findDistPrefOrDefault,
                                      getInternalPackages,
                                      computeComponentId,
                                      computeCompatPackageKey,
                                      computeCompatPackageName,
                                      localBuildInfoFile,
                                      getInstalledPackages,
                                      getInstalledPackagesMonitorFiles,
                                      getPackageDBContents,
                                      configCompiler, configCompilerAux,
                                      configCompilerEx, configCompilerAuxEx,
                                      computeEffectiveProfiling,
                                      ccLdOptionsBuildInfo,
                                      checkForeignDeps,
                                      interpretPackageDbFlags,
                                      ConfigStateFileError(..),
                                      tryGetConfigStateFile,
                                      platformDefines,
                                     )
    where

import Prelude ()
import Distribution.Compat.Prelude

import Distribution.Compiler
import Distribution.Types.IncludeRenaming
import Distribution.Utils.NubList
import Distribution.Simple.Compiler hiding (Flag)
import Distribution.Simple.PreProcess
import Distribution.Package
import qualified Distribution.InstalledPackageInfo as Installed
import Distribution.InstalledPackageInfo (InstalledPackageInfo)
import qualified Distribution.Simple.PackageIndex as PackageIndex
import Distribution.Simple.PackageIndex (InstalledPackageIndex)
import Distribution.PackageDescription as PD hiding (Flag)
import Distribution.Types.PackageDescription as PD
import Distribution.PackageDescription.PrettyPrint
import Distribution.PackageDescription.Configuration
import Distribution.PackageDescription.Check hiding (doesFileExist)
import Distribution.Simple.BuildToolDepends
import Distribution.Simple.Program
import Distribution.Simple.Setup as Setup
import Distribution.Simple.BuildTarget
import Distribution.Simple.LocalBuildInfo
import Distribution.Types.ExeDependency
import Distribution.Types.LegacyExeDependency
import Distribution.Types.PkgconfigDependency
import Distribution.Types.MungedPackageName
import Distribution.Types.LocalBuildInfo
import Distribution.Types.ComponentRequestedSpec
import Distribution.Types.ForeignLib
import Distribution.Types.ForeignLibType
import Distribution.Types.ForeignLibOption
import Distribution.Types.Mixin
import Distribution.Types.UnqualComponentName
import Distribution.Simple.Utils
import Distribution.System
import Distribution.Version
import Distribution.Verbosity
import qualified Distribution.Compat.Graph as Graph
import Distribution.Compat.Stack
import Distribution.Backpack.Configure
import Distribution.Backpack.DescribeUnitId
import Distribution.Backpack.PreExistingComponent
import Distribution.Backpack.ConfiguredComponent (newPackageDepsBehaviour)
import Distribution.Backpack.Id
import Distribution.Utils.LogProgress

import qualified Distribution.Simple.GHC   as GHC
import qualified Distribution.Simple.GHCJS as GHCJS
import qualified Distribution.Simple.JHC   as JHC
import qualified Distribution.Simple.LHC   as LHC
import qualified Distribution.Simple.UHC   as UHC
import qualified Distribution.Simple.HaskellSuite as HaskellSuite

import Control.Exception
    ( ErrorCall, Exception, evaluate, throw, throwIO, try )
import Distribution.Compat.Binary ( decodeOrFailIO, encode )
import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString            as BS
import qualified Data.ByteString.Lazy.Char8 as BLC8
import Data.List
    ( (\\), partition, inits, stripPrefix )
import Data.Either
    ( partitionEithers )
import qualified Data.Map as Map
import System.Directory
    ( doesFileExist, createDirectoryIfMissing, getTemporaryDirectory )
import System.FilePath
    ( (</>), isAbsolute )
import qualified System.Info
    ( compilerName, compilerVersion )
import System.IO
    ( hPutStrLn, hClose )
import Distribution.Text
    ( Text(disp), defaultStyle, display, simpleParse )
import Text.PrettyPrint
    ( Doc, (<+>), ($+$), char, comma, hsep, nest
    , punctuate, quotes, render, renderStyle, sep, text )
import Distribution.Compat.Environment ( lookupEnv )
import Distribution.Compat.Exception ( catchExit, catchIO )

type UseExternalInternalDeps = Bool

-- | The errors that can be thrown when reading the @setup-config@ file.
data ConfigStateFileError
    = ConfigStateFileNoHeader -- ^ No header found.
    | ConfigStateFileBadHeader -- ^ Incorrect header.
    | ConfigStateFileNoParse -- ^ Cannot parse file contents.
    | ConfigStateFileMissing -- ^ No file!
    | ConfigStateFileBadVersion PackageIdentifier PackageIdentifier
      (Either ConfigStateFileError LocalBuildInfo) -- ^ Mismatched version.
  deriving (Typeable)

-- | Format a 'ConfigStateFileError' as a user-facing error message.
dispConfigStateFileError :: ConfigStateFileError -> Doc
dispConfigStateFileError ConfigStateFileNoHeader =
    text "Saved package config file header is missing."
    <+> text "Re-run the 'configure' command."
dispConfigStateFileError ConfigStateFileBadHeader =
    text "Saved package config file header is corrupt."
    <+> text "Re-run the 'configure' command."
dispConfigStateFileError ConfigStateFileNoParse =
    text "Saved package config file is corrupt."
    <+> text "Re-run the 'configure' command."
dispConfigStateFileError ConfigStateFileMissing =
    text "Run the 'configure' command first."
dispConfigStateFileError (ConfigStateFileBadVersion oldCabal oldCompiler _) =
    text "Saved package config file is outdated:"
    $+$ badCabal $+$ badCompiler
    $+$ text "Re-run the 'configure' command."
    where
      badCabal =
          text "• the Cabal version changed from"
          <+> disp oldCabal <+> "to" <+> disp currentCabalId
      badCompiler
        | oldCompiler == currentCompilerId = mempty
        | otherwise =
            text "• the compiler changed from"
            <+> disp oldCompiler <+> "to" <+> disp currentCompilerId

instance Show ConfigStateFileError where
    show = renderStyle defaultStyle . dispConfigStateFileError

instance Exception ConfigStateFileError

-- | Read the 'localBuildInfoFile'.  Throw an exception if the file is
-- missing, if the file cannot be read, or if the file was created by an older
-- version of Cabal.
getConfigStateFile :: FilePath -- ^ The file path of the @setup-config@ file.
                   -> IO LocalBuildInfo
getConfigStateFile filename = do
    exists <- doesFileExist filename
    unless exists $ throwIO ConfigStateFileMissing
    -- Read the config file into a strict ByteString to avoid problems with
    -- lazy I/O, then convert to lazy because the binary package needs that.
    contents <- BS.readFile filename
    let (header, body) = BLC8.span (/='\n') (BLC8.fromChunks [contents])

    headerParseResult <- try $ evaluate $ parseHeader header
    let (cabalId, compId) =
            case headerParseResult of
              Left (_ :: ErrorCall) -> throw ConfigStateFileBadHeader
              Right x -> x

    let getStoredValue = do
          result <- decodeOrFailIO (BLC8.tail body)
          case result of
            Left _ -> throw ConfigStateFileNoParse
            Right x -> return x
        deferErrorIfBadVersion act
          | cabalId /= currentCabalId = do
              eResult <- try act
              throw $ ConfigStateFileBadVersion cabalId compId eResult
          | otherwise = act
    deferErrorIfBadVersion getStoredValue
  where
    _ = callStack -- TODO: attach call stack to exception

-- | Read the 'localBuildInfoFile', returning either an error or the local build
-- info.
tryGetConfigStateFile :: FilePath -- ^ The file path of the @setup-config@ file.
                      -> IO (Either ConfigStateFileError LocalBuildInfo)
tryGetConfigStateFile = try . getConfigStateFile

-- | Try to read the 'localBuildInfoFile'.
tryGetPersistBuildConfig :: FilePath -- ^ The @dist@ directory path.
                         -> IO (Either ConfigStateFileError LocalBuildInfo)
tryGetPersistBuildConfig = try . getPersistBuildConfig

-- | Read the 'localBuildInfoFile'. Throw an exception if the file is
-- missing, if the file cannot be read, or if the file was created by an older
-- version of Cabal.
getPersistBuildConfig :: FilePath -- ^ The @dist@ directory path.
                      -> IO LocalBuildInfo
getPersistBuildConfig = getConfigStateFile . localBuildInfoFile

-- | Try to read the 'localBuildInfoFile'.
maybeGetPersistBuildConfig :: FilePath -- ^ The @dist@ directory path.
                           -> IO (Maybe LocalBuildInfo)
maybeGetPersistBuildConfig =
    liftM (either (const Nothing) Just) . tryGetPersistBuildConfig

-- | After running configure, output the 'LocalBuildInfo' to the
-- 'localBuildInfoFile'.
writePersistBuildConfig :: FilePath -- ^ The @dist@ directory path.
                        -> LocalBuildInfo -- ^ The 'LocalBuildInfo' to write.
                        -> NoCallStackIO ()
writePersistBuildConfig distPref lbi = do
    createDirectoryIfMissing False distPref
    writeFileAtomic (localBuildInfoFile distPref) $
      BLC8.unlines [showHeader pkgId, encode lbi]
  where
    pkgId = localPackage lbi

-- | Identifier of the current Cabal package.
currentCabalId :: PackageIdentifier
currentCabalId = PackageIdentifier (mkPackageName "Cabal") cabalVersion

-- | Identifier of the current compiler package.
currentCompilerId :: PackageIdentifier
currentCompilerId = PackageIdentifier (mkPackageName System.Info.compilerName)
                                      (mkVersion' System.Info.compilerVersion)

-- | Parse the @setup-config@ file header, returning the package identifiers
-- for Cabal and the compiler.
parseHeader :: ByteString -- ^ The file contents.
            -> (PackageIdentifier, PackageIdentifier)
parseHeader header = case BLC8.words header of
  ["Saved", "package", "config", "for", pkgId, "written", "by", cabalId,
   "using", compId] ->
      fromMaybe (throw ConfigStateFileBadHeader) $ do
          _ <- simpleParse (BLC8.unpack pkgId) :: Maybe PackageIdentifier
          cabalId' <- simpleParse (BLC8.unpack cabalId)
          compId' <- simpleParse (BLC8.unpack compId)
          return (cabalId', compId')
  _ -> throw ConfigStateFileNoHeader

-- | Generate the @setup-config@ file header.
showHeader :: PackageIdentifier -- ^ The processed package.
            -> ByteString
showHeader pkgId = BLC8.unwords
    [ "Saved", "package", "config", "for"
    , BLC8.pack $ display pkgId
    , "written", "by"
    , BLC8.pack $ display currentCabalId
    , "using"
    , BLC8.pack $ display currentCompilerId
    ]

-- | Check that localBuildInfoFile is up-to-date with respect to the
-- .cabal file.
checkPersistBuildConfigOutdated :: FilePath -> FilePath -> NoCallStackIO Bool
checkPersistBuildConfigOutdated distPref pkg_descr_file =
  pkg_descr_file `moreRecentFile` localBuildInfoFile distPref

-- | Get the path of @dist\/setup-config@.
localBuildInfoFile :: FilePath -- ^ The @dist@ directory path.
                    -> FilePath
localBuildInfoFile distPref = distPref </> "setup-config"

-- -----------------------------------------------------------------------------
-- * Configuration
-- -----------------------------------------------------------------------------

-- | Return the \"dist/\" prefix, or the default prefix. The prefix is taken
-- from (in order of highest to lowest preference) the override prefix, the
-- \"CABAL_BUILDDIR\" environment variable, or the default prefix.
findDistPref :: FilePath  -- ^ default \"dist\" prefix
             -> Setup.Flag FilePath  -- ^ override \"dist\" prefix
             -> NoCallStackIO FilePath
findDistPref defDistPref overrideDistPref = do
    envDistPref <- liftM parseEnvDistPref (lookupEnv "CABAL_BUILDDIR")
    return $ fromFlagOrDefault defDistPref (mappend envDistPref overrideDistPref)
  where
    parseEnvDistPref env =
      case env of
        Just distPref | not (null distPref) -> toFlag distPref
        _ -> NoFlag

-- | Return the \"dist/\" prefix, or the default prefix. The prefix is taken
-- from (in order of highest to lowest preference) the override prefix, the
-- \"CABAL_BUILDDIR\" environment variable, or 'defaultDistPref' is used. Call
-- this function to resolve a @*DistPref@ flag whenever it is not known to be
-- set. (The @*DistPref@ flags are always set to a definite value before
-- invoking 'UserHooks'.)
findDistPrefOrDefault :: Setup.Flag FilePath  -- ^ override \"dist\" prefix
                      -> NoCallStackIO FilePath
findDistPrefOrDefault = findDistPref defaultDistPref

-- |Perform the \"@.\/setup configure@\" action.
-- Returns the @.setup-config@ file.
configure :: (GenericPackageDescription, HookedBuildInfo)
          -> ConfigFlags -> IO LocalBuildInfo
configure (pkg_descr0, pbi) cfg = do
    -- Determine the component we are configuring, if a user specified
    -- one on the command line.  We use a fake, flattened version of
    -- the package since at this point, we're not really sure what
    -- components we *can* configure.  @Nothing@ means that we should
    -- configure everything (the old behavior).
    (mb_cname :: Maybe ComponentName) <- do
        let flat_pkg_descr = flattenPackageDescription pkg_descr0
        targets <- readBuildTargets verbosity flat_pkg_descr (configArgs cfg)
        -- TODO: bleat if you use the module/file syntax
        let targets' = [ cname | BuildTargetComponent cname <- targets ]
        case targets' of
            _ | null (configArgs cfg) -> return Nothing
            [cname] -> return (Just cname)
            [] -> die' verbosity "No valid component targets found"
            _ -> die' verbosity "Can only configure either single component or all of them"

    let use_external_internal_deps = isJust mb_cname
    case mb_cname of
        Nothing -> setupMessage verbosity "Configuring" (packageId pkg_descr0)
        Just cname -> setupMessage' verbosity "Configuring" (packageId pkg_descr0)
                        cname (Just (configInstantiateWith cfg))

    -- configCID is only valid for per-component configure
    when (isJust (flagToMaybe (configCID cfg)) && isNothing mb_cname) $
        die' verbosity "--cid is only supported for per-component configure"

    checkDeprecatedFlags verbosity cfg
    checkExactConfiguration verbosity pkg_descr0 cfg

    -- Where to build the package
    let buildDir :: FilePath -- e.g. dist/build
        -- fromFlag OK due to Distribution.Simple calling
        -- findDistPrefOrDefault to fill it in
        buildDir = fromFlag (configDistPref cfg) </> "build"
    createDirectoryIfMissingVerbose (lessVerbose verbosity) True buildDir

    -- What package database(s) to use
    let packageDbs :: PackageDBStack
        packageDbs
         = interpretPackageDbFlags
            (fromFlag (configUserInstall cfg))
            (configPackageDBs cfg)

    -- comp:            the compiler we're building with
    -- compPlatform:    the platform we're building for
    -- programDb:  location and args of all programs we're
    --                  building with
    (comp         :: Compiler,
     compPlatform :: Platform,
     programDb    :: ProgramDb)
        <- configCompilerEx
            (flagToMaybe (configHcFlavor cfg))
            (flagToMaybe (configHcPath cfg))
            (flagToMaybe (configHcPkg cfg))
            (mkProgramDb cfg (configPrograms cfg))
            (lessVerbose verbosity)

    -- The InstalledPackageIndex of all installed packages
    installedPackageSet :: InstalledPackageIndex
        <- getInstalledPackages (lessVerbose verbosity) comp
                                  packageDbs programDb

    -- The set of package names which are "shadowed" by internal
    -- packages, and which component they map to
    let internalPackageSet :: Map PackageName (Maybe UnqualComponentName)
        internalPackageSet = getInternalPackages pkg_descr0

    -- Make a data structure describing what components are enabled.
    let enabled :: ComponentRequestedSpec
        enabled = case mb_cname of
                    Just cname -> OneComponentRequestedSpec cname
                    Nothing -> ComponentRequestedSpec
                                -- The flag name (@--enable-tests@) is a
                                -- little bit of a misnomer, because
                                -- just passing this flag won't
                                -- "enable", in our internal
                                -- nomenclature; it's just a request; a
                                -- @buildable: False@ might make it
                                -- not possible to enable.
                                { testsRequested = fromFlag (configTests cfg)
                                , benchmarksRequested =
                                  fromFlag (configBenchmarks cfg) }
    -- Some sanity checks related to enabling components.
    when (isJust mb_cname
          && (fromFlag (configTests cfg) || fromFlag (configBenchmarks cfg))) $
        die' verbosity $ "--enable-tests/--enable-benchmarks are incompatible with" ++
              " explicitly specifying a component to configure."

    -- allConstraints:  The set of all 'Dependency's we have.  Used ONLY
    --                  to 'configureFinalizedPackage'.
    -- requiredDepsMap: A map from 'PackageName' to the specifically
    --                  required 'InstalledPackageInfo', due to --dependency
    --
    -- NB: These constraints are to be applied to ALL components of
    -- a package.  Thus, it's not an error if allConstraints contains
    -- more constraints than is necessary for a component (another
    -- component might need it.)
    --
    -- NB: The fact that we bundle all the constraints together means
    -- that is not possible to configure a test-suite to use one
    -- version of a dependency, and the executable to use another.
    (allConstraints  :: [Dependency],
     requiredDepsMap :: Map PackageName InstalledPackageInfo)
        <- either (die' verbosity) return $
              combinedConstraints (configConstraints cfg)
                                  (configDependencies cfg)
                                  installedPackageSet

    -- pkg_descr:   The resolved package description, that does not contain any
    --              conditionals, because we have have an assignment for
    --              every flag, either picking them ourselves using a
    --              simple naive algorithm, or having them be passed to
    --              us by 'configConfigurationsFlags')
    -- flags:       The 'FlagAssignment' that the conditionals were
    --              resolved with.
    --
    -- NB: Why doesn't finalizing a package also tell us what the
    -- dependencies are (e.g. when we run the naive algorithm,
    -- we are checking if dependencies are satisfiable)?  The
    -- primary reason is that we may NOT have done any solving:
    -- if the flags are all chosen for us, this step is a simple
    -- matter of flattening according to that assignment.  It's
    -- cleaner to then configure the dependencies afterwards.
    (pkg_descr :: PackageDescription,
     flags     :: FlagAssignment)
        <- configureFinalizedPackage verbosity cfg enabled
                allConstraints
                (dependencySatisfiable
                    use_external_internal_deps
                    (fromFlagOrDefault False (configExactConfiguration cfg))
                    (packageName pkg_descr0)
                    installedPackageSet
                    internalPackageSet
                    requiredDepsMap)
                comp
                compPlatform
                pkg_descr0

    debug verbosity $ "Finalized package description:\n"
                  ++ showPackageDescription pkg_descr
    -- NB: showPackageDescription does not display the AWFUL HACK GLOBAL
    -- buildDepends, so we have to display it separately.  See #2066
    -- Some day, we should eliminate this, so that
    -- configureFinalizedPackage returns the set of overall dependencies
    -- separately.  Then 'configureDependencies' and
    -- 'Distribution.PackageDescription.Check' need to be adjusted
    -- accordingly.
    debug verbosity $ "Finalized build-depends: "
                  ++ intercalate ", " (map display (buildDepends pkg_descr))

    checkCompilerProblems verbosity comp pkg_descr enabled
    checkPackageProblems verbosity pkg_descr0
        (updatePackageDescription pbi pkg_descr)

    -- The list of 'InstalledPackageInfo' recording the selected
    -- dependencies on external packages.
    --
    -- Invariant: For any package name, there is at most one package
    -- in externalPackageDeps which has that name.
    --
    -- NB: The dependency selection is global over ALL components
    -- in the package (similar to how allConstraints and
    -- requiredDepsMap are global over all components).  In particular,
    -- if *any* component (post-flag resolution) has an unsatisfiable
    -- dependency, we will fail.  This can sometimes be undesirable
    -- for users, see #1786 (benchmark conflicts with executable),
    --
    -- In the presence of Backpack, these package dependencies are
    -- NOT complete: they only ever include the INDEFINITE
    -- dependencies.  After we apply an instantiation, we'll get
    -- definite references which constitute extra dependencies.
    -- (Why not have cabal-install pass these in explicitly?
    -- For one it's deterministic; for two, we need to associate
    -- them with renamings which would require a far more complicated
    -- input scheme than what we have today.)
    externalPkgDeps :: [PreExistingComponent]
        <- configureDependencies
                verbosity
                use_external_internal_deps
                internalPackageSet
                installedPackageSet
                requiredDepsMap
                pkg_descr

    -- Compute installation directory templates, based on user
    -- configuration.
    --
    -- TODO: Move this into a helper function.
    defaultDirs :: InstallDirTemplates
        <- defaultInstallDirs' use_external_internal_deps
                              (compilerFlavor comp)
                              (fromFlag (configUserInstall cfg))
                              (hasLibs pkg_descr)
    let installDirs :: InstallDirTemplates
        installDirs = combineInstallDirs fromFlagOrDefault
                        defaultDirs (configInstallDirs cfg)

    -- Check languages and extensions
    -- TODO: Move this into a helper function.
    let langlist = nub $ catMaybes $ map defaultLanguage
                   (enabledBuildInfos pkg_descr enabled)
    let langs = unsupportedLanguages comp langlist
    when (not (null langs)) $
      die' verbosity $ "The package " ++ display (packageId pkg_descr0)
         ++ " requires the following languages which are not "
         ++ "supported by " ++ display (compilerId comp) ++ ": "
         ++ intercalate ", " (map display langs)
    let extlist = nub $ concatMap allExtensions (enabledBuildInfos pkg_descr enabled)
    let exts = unsupportedExtensions comp extlist
    when (not (null exts)) $
      die' verbosity $ "The package " ++ display (packageId pkg_descr0)
         ++ " requires the following language extensions which are not "
         ++ "supported by " ++ display (compilerId comp) ++ ": "
         ++ intercalate ", " (map display exts)

    -- Check foreign library build requirements
    let flibs = [flib | CFLib flib <- enabledComponents pkg_descr enabled]
    let unsupportedFLibs = unsupportedForeignLibs comp compPlatform flibs
    when (not (null unsupportedFLibs)) $
      die' verbosity $ "Cannot build some foreign libraries: "
         ++ intercalate "," unsupportedFLibs

    -- Configure certain external build tools, see below for which ones.
    let requiredBuildTools = do
          bi <- enabledBuildInfos pkg_descr enabled
          -- First, we collect any tool dep that we know is external. This is,
          -- in practice:
          --
          -- 1. `build-tools` entries on the whitelist
          --
          -- 2. `build-tool-depends` that aren't from the current package.
          let externBuildToolDeps =
                [ LegacyExeDependency (unUnqualComponentName eName) versionRange
                | buildTool@(ExeDependency _ eName versionRange)
                  <- getAllToolDependencies pkg_descr bi
                , not $ isInternal pkg_descr buildTool ]
          -- Second, we collect any build-tools entry we don't know how to
          -- desugar. We'll never have any idea how to build them, so we just
          -- hope they are already on the PATH.
          let unknownBuildTools =
                [ buildTool
                | buildTool <- buildTools bi
                , Nothing == desugarBuildTool pkg_descr buildTool ]
          externBuildToolDeps ++ unknownBuildTools

    programDb' <-
          configureAllKnownPrograms (lessVerbose verbosity) programDb
      >>= configureRequiredPrograms verbosity requiredBuildTools

    (pkg_descr', programDb'') <-
      configurePkgconfigPackages verbosity pkg_descr programDb' enabled

    -- Compute internal component graph
    --
    -- The general idea is that we take a look at all the source level
    -- components (which may build-depends on each other) and form a graph.
    -- From there, we build a ComponentLocalBuildInfo for each of the
    -- components, which lets us actually build each component.
    -- internalPackageSet
    -- use_external_internal_deps
    (buildComponents :: [ComponentLocalBuildInfo],
     packageDependsIndex :: InstalledPackageIndex) <-
      runLogProgress verbosity $ configureComponentLocalBuildInfos
            verbosity
            use_external_internal_deps
            enabled
            (fromFlagOrDefault False (configDeterministic cfg))
            (configIPID cfg)
            (configCID cfg)
            pkg_descr
            externalPkgDeps
            (configConfigurationsFlags cfg)
            (configInstantiateWith cfg)
            installedPackageSet
            comp

    -- Decide if we're going to compile with split sections.
    split_sections :: Bool <-
       if not (fromFlag $ configSplitSections cfg)
            then return False
            else case compilerFlavor comp of
                        GHC | compilerVersion comp >= mkVersion [8,0]
                          -> return True
                        GHCJS
                          -> return True
                        _ -> do warn verbosity
                                     ("this compiler does not support " ++
                                      "--enable-split-sections; ignoring")
                                return False

    -- Decide if we're going to compile with split objects.
    split_objs :: Bool <-
       if not (fromFlag $ configSplitObjs cfg)
            then return False
            else case compilerFlavor comp of
                        _ | split_sections
                          -> do warn verbosity
                                     ("--enable-split-sections and " ++
                                      "--enable-split-objs are mutually" ++
                                      "exclusive; ignoring the latter")
                                return False
                        GHC | compilerVersion comp >= mkVersion [6,5]
                          -> return True
                        GHCJS
                          -> return True
                        _ -> do warn verbosity
                                     ("this compiler does not support " ++
                                      "--enable-split-objs; ignoring")
                                return False

    let ghciLibByDefault =
          case compilerId comp of
            CompilerId GHC _ ->
              -- If ghc is non-dynamic, then ghci needs object files,
              -- so we build one by default.
              --
              -- Technically, archive files should be sufficient for ghci,
              -- but because of GHC bug #8942, it has never been safe to
              -- rely on them. By the time that bug was fixed, ghci had
              -- been changed to read shared libraries instead of archive
              -- files (see next code block).
              not (GHC.isDynamic comp)
            CompilerId GHCJS _ ->
              not (GHCJS.isDynamic comp)
            _ -> False

    let sharedLibsByDefault
          | fromFlag (configDynExe cfg) =
              -- build a shared library if dynamically-linked
              -- executables are requested
              True
          | otherwise = case compilerId comp of
            CompilerId GHC _ ->
              -- if ghc is dynamic, then ghci needs a shared
              -- library, so we build one by default.
              GHC.isDynamic comp
            CompilerId GHCJS _ ->
              GHCJS.isDynamic comp
            _ -> False
        withSharedLib_ =
            -- build shared libraries if required by GHC or by the
            -- executable linking mode, but allow the user to force
            -- building only static library archives with
            -- --disable-shared.
            fromFlagOrDefault sharedLibsByDefault $ configSharedLib cfg

        withStaticLib_ =
            -- build a static library (all dependent libraries rolled
            -- into a huge .a archive) via GHCs -staticlib flag.
            fromFlagOrDefault False $ configStaticLib cfg

        withDynExe_ = fromFlag $ configDynExe cfg
    when (withDynExe_ && not withSharedLib_) $ warn verbosity $
           "Executables will use dynamic linking, but a shared library "
        ++ "is not being built. Linking will fail if any executables "
        ++ "depend on the library."

    setProfLBI <- configureProfiling verbosity cfg comp

    setCoverageLBI <- configureCoverage verbosity cfg comp

    let reloc = fromFlagOrDefault False $ configRelocatable cfg

    let buildComponentsMap =
            foldl' (\m clbi -> Map.insertWith (++)
                               (componentLocalName clbi) [clbi] m)
                   Map.empty buildComponents

    let lbi = (setCoverageLBI . setProfLBI)
              LocalBuildInfo {
                configFlags         = cfg,
                flagAssignment      = flags,
                componentEnabledSpec = enabled,
                extraConfigArgs     = [],  -- Currently configure does not
                                           -- take extra args, but if it
                                           -- did they would go here.
                installDirTemplates = installDirs,
                compiler            = comp,
                hostPlatform        = compPlatform,
                buildDir            = buildDir,
                componentGraph      = Graph.fromDistinctList buildComponents,
                componentNameMap    = buildComponentsMap,
                installedPkgs       = packageDependsIndex,
                pkgDescrFile        = Nothing,
                localPkgDescr       = pkg_descr',
                withPrograms        = programDb'',
                withVanillaLib      = fromFlag $ configVanillaLib cfg,
                withSharedLib       = withSharedLib_,
                withStaticLib       = withStaticLib_,
                withDynExe          = withDynExe_,
                withProfLib         = False,
                withProfLibDetail   = ProfDetailNone,
                withProfExe         = False,
                withProfExeDetail   = ProfDetailNone,
                withOptimization    = fromFlag $ configOptimization cfg,
                withDebugInfo       = fromFlag $ configDebugInfo cfg,
                withGHCiLib         = fromFlagOrDefault ghciLibByDefault $
                                      configGHCiLib cfg,
                splitSections       = split_sections,
                splitObjs           = split_objs,
                stripExes           = fromFlag $ configStripExes cfg,
                stripLibs           = fromFlag $ configStripLibs cfg,
                exeCoverage         = False,
                libCoverage         = False,
                withPackageDB       = packageDbs,
                progPrefix          = fromFlag $ configProgPrefix cfg,
                progSuffix          = fromFlag $ configProgSuffix cfg,
                relocatable         = reloc
              }

    when reloc (checkRelocatable verbosity pkg_descr lbi)

    -- TODO: This is not entirely correct, because the dirs may vary
    -- across libraries/executables
    let dirs = absoluteInstallDirs pkg_descr lbi NoCopyDest
        relative = prefixRelativeInstallDirs (packageId pkg_descr) lbi

    unless (isAbsolute (prefix dirs)) $ die' verbosity $
        "expected an absolute directory name for --prefix: " ++ prefix dirs

    info verbosity $ "Using " ++ display currentCabalId
                  ++ " compiled by " ++ display currentCompilerId
    info verbosity $ "Using compiler: " ++ showCompilerId comp
    info verbosity $ "Using install prefix: " ++ prefix dirs

    let dirinfo name dir isPrefixRelative =
          info verbosity $ name ++ " installed in: " ++ dir ++ relNote
          where relNote = case buildOS of
                  Windows | not (hasLibs pkg_descr)
                         && isNothing isPrefixRelative
                         -> "  (fixed location)"
                  _      -> ""

    dirinfo "Executables"      (bindir dirs)     (bindir relative)
    dirinfo "Libraries"        (libdir dirs)     (libdir relative)
    dirinfo "Dynamic Libraries" (dynlibdir dirs) (dynlibdir relative)
    dirinfo "Private executables" (libexecdir dirs) (libexecdir relative)
    dirinfo "Data files"       (datadir dirs)    (datadir relative)
    dirinfo "Documentation"    (docdir dirs)     (docdir relative)
    dirinfo "Configuration files" (sysconfdir dirs) (sysconfdir relative)

    sequence_ [ reportProgram verbosity prog configuredProg
              | (prog, configuredProg) <- knownPrograms programDb'' ]

    return lbi

    where
      verbosity = fromFlag (configVerbosity cfg)

mkProgramDb :: ConfigFlags -> ProgramDb -> ProgramDb
mkProgramDb cfg initialProgramDb = programDb
  where
    programDb  = userSpecifyArgss (configProgramArgs cfg)
                 . userSpecifyPaths (configProgramPaths cfg)
                 . setProgramSearchPath searchpath
                 $ initialProgramDb
    searchpath = getProgramSearchPath initialProgramDb
                 ++ map ProgramSearchPathDir
                 (fromNubList $ configProgramPathExtra cfg)

-- -----------------------------------------------------------------------------
-- Helper functions for configure

-- | Check if the user used any deprecated flags.
checkDeprecatedFlags :: Verbosity -> ConfigFlags -> IO ()
checkDeprecatedFlags verbosity cfg = do
    unless (configProfExe cfg == NoFlag) $ do
      let enable | fromFlag (configProfExe cfg) = "enable"
                 | otherwise = "disable"
      warn verbosity
        ("The flag --" ++ enable ++ "-executable-profiling is deprecated. "
         ++ "Please use --" ++ enable ++ "-profiling instead.")

    unless (configLibCoverage cfg == NoFlag) $ do
      let enable | fromFlag (configLibCoverage cfg) = "enable"
                 | otherwise = "disable"
      warn verbosity
        ("The flag --" ++ enable ++ "-library-coverage is deprecated. "
         ++ "Please use --" ++ enable ++ "-coverage instead.")

-- | Sanity check: if '--exact-configuration' was given, ensure that the
-- complete flag assignment was specified on the command line.
checkExactConfiguration :: Verbosity -> GenericPackageDescription -> ConfigFlags -> IO ()
checkExactConfiguration verbosity pkg_descr0 cfg =
    when (fromFlagOrDefault False (configExactConfiguration cfg)) $ do
      let cmdlineFlags = map fst (unFlagAssignment (configConfigurationsFlags cfg))
          allFlags     = map flagName . genPackageFlags $ pkg_descr0
          diffFlags    = allFlags \\ cmdlineFlags
      when (not . null $ diffFlags) $
        die' verbosity $ "'--exact-configuration' was given, "
        ++ "but the following flags were not specified: "
        ++ intercalate ", " (map show diffFlags)

-- | Create a PackageIndex that makes *any libraries that might be*
-- defined internally to this package look like installed packages, in
-- case an executable should refer to any of them as dependencies.
--
-- It must be *any libraries that might be* defined rather than the
-- actual definitions, because these depend on conditionals in the .cabal
-- file, and we haven't resolved them yet.  finalizePD
-- does the resolution of conditionals, and it takes internalPackageSet
-- as part of its input.
getInternalPackages :: GenericPackageDescription
                    -> Map PackageName (Maybe UnqualComponentName)
getInternalPackages pkg_descr0 =
    -- TODO: some day, executables will be fair game here too!
    let pkg_descr = flattenPackageDescription pkg_descr0
        f lib = case libName lib of
                    Nothing -> (packageName pkg_descr, Nothing)
                    Just n' -> (unqualComponentNameToPackageName n', Just n')
    in Map.fromList (map f (allLibraries pkg_descr))

-- | Returns true if a dependency is satisfiable.  This function may
-- report a dependency satisfiable even when it is not, but not vice
-- versa. This is to be passed to finalizePD.
dependencySatisfiable
    :: Bool -- ^ use external internal deps?
    -> Bool -- ^ exact configuration?
    -> PackageName
    -> InstalledPackageIndex -- ^ installed set
    -> Map PackageName (Maybe UnqualComponentName) -- ^ internal set
    -> Map PackageName InstalledPackageInfo -- ^ required dependencies
    -> (Dependency -> Bool)
dependencySatisfiable
  use_external_internal_deps
  exact_config pn installedPackageSet internalPackageSet requiredDepsMap
  d@(Dependency depName vr)

    | exact_config
    -- When we're given '--exact-configuration', we assume that all
    -- dependencies and flags are exactly specified on the command
    -- line. Thus we only consult the 'requiredDepsMap'. Note that
    -- we're not doing the version range check, so if there's some
    -- dependency that wasn't specified on the command line,
    -- 'finalizePD' will fail.
    -- TODO: mention '--exact-configuration' in the error message
    -- when this fails?
    = if isInternalDep && not use_external_internal_deps
        -- Except for internal deps, when we're NOT per-component mode;
        -- those are just True.
        then True
        else depName `Map.member` requiredDepsMap

    | isInternalDep
    = if use_external_internal_deps
        -- When we are doing per-component configure, we now need to
        -- test if the internal dependency is in the index.  This has
        -- DIFFERENT semantics from normal dependency satisfiability.
        then internalDepSatisfiable
        -- If a 'PackageName' is defined by an internal component, the dep is
        -- satisfiable (we're going to build it ourselves)
        else True

    | otherwise
    = depSatisfiable

  where
    isInternalDep = Map.member depName internalPackageSet

    depSatisfiable =
        not . null $ PackageIndex.lookupDependency installedPackageSet d

    internalDepSatisfiable =
        not . null $ PackageIndex.lookupInternalDependency
                        installedPackageSet (Dependency pn vr) cn
      where
        cn | pn == depName
           = Nothing
           | otherwise
           -- Reinterpret the "package name" as an unqualified component
           -- name
           = Just (mkUnqualComponentName (unPackageName depName))

-- | Finalize a generic package description.  The workhorse is
-- 'finalizePD' but there's a bit of other nattering
-- about necessary.
--
-- TODO: what exactly is the business with @flaggedTests@ and
-- @flaggedBenchmarks@?
configureFinalizedPackage
    :: Verbosity
    -> ConfigFlags
    -> ComponentRequestedSpec
    -> [Dependency]
    -> (Dependency -> Bool) -- ^ tests if a dependency is satisfiable.
                            -- Might say it's satisfiable even when not.
    -> Compiler
    -> Platform
    -> GenericPackageDescription
    -> IO (PackageDescription, FlagAssignment)
configureFinalizedPackage verbosity cfg enabled
  allConstraints satisfies comp compPlatform pkg_descr0 = do

    (pkg_descr0', flags) <-
            case finalizePD
                   (configConfigurationsFlags cfg)
                   enabled
                   satisfies
                   compPlatform
                   (compilerInfo comp)
                   allConstraints
                   pkg_descr0
            of Right r -> return r
               Left missing ->
                   die' verbosity $ "Encountered missing dependencies:\n"
                     ++ (render . nest 4 . sep . punctuate comma
                                . map (disp . simplifyDependency)
                                $ missing)

    -- add extra include/lib dirs as specified in cfg
    -- we do it here so that those get checked too
    let pkg_descr = addExtraIncludeLibDirs pkg_descr0'

    unless (nullFlagAssignment flags) $
      info verbosity $ "Flags chosen: "
                    ++ intercalate ", " [ unFlagName fn ++ "=" ++ display value
                                        | (fn, value) <- unFlagAssignment flags ]

    return (pkg_descr, flags)
  where
    addExtraIncludeLibDirs pkg_descr =
        let extraBi = mempty { extraLibDirs = configExtraLibDirs cfg
                             , extraFrameworkDirs = configExtraFrameworkDirs cfg