Shortcut helper compilation when Cabal version is already available

This is mostly an optimization for Nix which already sets up the environment
correctly, so we should reward its users :)

6 files changed, 852 insertions, 815 deletions

diff --git a/cabal-helper.cabal b/cabal-helper.cabal
index a9d9715..9c8e995 100644
--- a/cabal-helper.cabal
+++ b/cabal-helper.cabal
@@ -142,6 +142,8 @@ library c-h-internal
                        CabalHelper.Compiletime.Sandbox
                        CabalHelper.Compiletime.Types
                        CabalHelper.Compiletime.Types.RelativePath
+                       CabalHelper.Runtime.Compat
+                       CabalHelper.Runtime.HelperMain
                        CabalHelper.Shared.Common
                        CabalHelper.Shared.InterfaceTypes
   other-modules:
@@ -193,6 +195,7 @@ executable cabal-helper-main
   main-is:             CabalHelper/Runtime/Main.hs
   hs-source-dirs:      src
   other-modules:
+                       CabalHelper.Runtime.HelperMain
                        CabalHelper.Runtime.Compat
                        CabalHelper.Shared.Common
                        CabalHelper.Shared.InterfaceTypes
diff --git a/lib/Distribution/Helper.hs b/lib/Distribution/Helper.hs
index 95547c3..cabd97d 100644
--- a/lib/Distribution/Helper.hs
+++ b/lib/Distribution/Helper.hs
@@ -134,10 +134,11 @@ import CabalHelper.Compiletime.Types
 import CabalHelper.Compiletime.Types.RelativePath
 import CabalHelper.Shared.InterfaceTypes
 import CabalHelper.Shared.Common
+import CabalHelper.Runtime.HelperMain (helper_main)
 
 import CabalHelper.Compiletime.Compat.Version
 import qualified CabalHelper.Compiletime.Compat.ProgramDb as ProgDb
-    ( defaultProgramDb, programPath, lookupProgram, ghcProgram, ghcPkgProgram)
+    ( defaultProgramDb, programPath, lookupProgram, ghcProgram, ghcPkgProgram )
 
 import Distribution.System (buildPlatform)
 import Distribution.Text (display)
@@ -338,8 +339,8 @@ checkUpdateUnitInfo qe proj_info unit munit_info = do
   where
     reconf = do
       reconfigureUnit qe unit
-      helper <- getHelperExe proj_info qe
-      readUnitInfo qe helper unit
+      helper <- getHelper proj_info qe
+      readUnitInfo helper unit
 
 -- | Restrict 'UnitInfo' cache to units that are still active
 discardInactiveUnitInfos
@@ -470,10 +471,9 @@ readProjInfo qe pc pcm = withVerbosity $ do
         , ..
         }
 
-readUnitInfo :: QueryEnvI c pt -> FilePath -> Unit pt -> IO UnitInfo
-readUnitInfo
-  qe exe unit@Unit {uUnitId=uiUnitId, uCabalFile, uDistDir} = do
-    res <- readHelper qe exe uCabalFile uDistDir
+readUnitInfo :: Helper pt -> Unit pt -> IO UnitInfo
+readUnitInfo helper unit@Unit {uUnitId=uiUnitId} = do
+    res <- runHelper helper unit
            [ "package-id"
            , "package-db-stack"
            , "flags"
@@ -539,15 +539,15 @@ invokeHelper
 prepare :: QueryEnv pt -> IO ()
 prepare qe = do
   proj_info <- getProjInfo qe
-  void $ getHelperExe proj_info qe
+  void $ getHelper proj_info qe
 
 -- | Create @cabal_macros.h@ and @Paths_\<pkg\>@ possibly other generated files
 -- in the usual place. See 'Distribution.Simple.Build.initialBuildSteps'.
 writeAutogenFiles :: Unit pt -> Query pt ()
-writeAutogenFiles Unit{uCabalFile, uDistDir} = Query $ \qe -> do
+writeAutogenFiles unit = Query $ \qe -> do
   proj_info <- getProjInfo qe
-  exe <- getHelperExe proj_info qe
-  void $ invokeHelper qe exe uCabalFile uDistDir ["write-autogen-files"]
+  helper <- getHelper proj_info qe
+  void $ runHelper helper unit ["write-autogen-files"]
 
 -- | Get the path to the sandbox package-db in a project
 getSandboxPkgDb
@@ -618,11 +618,19 @@ withProgs impl QueryEnv{..} f = do
     same f o o'  = f o == f o'
     dprogs = defaultCompPrograms
 
-getHelperExe
-    :: ProjInfo pt -> QueryEnvI c pt -> IO FilePath
-getHelperExe proj_info qe@QueryEnv{..} = do
+newtype Helper pt
+  = Helper { runHelper :: Unit pt -> [String] -> IO [Maybe ChResponse] }
+
+getHelper :: ProjInfo pt -> QueryEnvI c pt -> IO (Helper pt)
+getHelper ProjInfo{piCabalVersion} QueryEnv{..}
+  | piCabalVersion == bultinCabalVersion = return $ Helper $
+      \Unit{ uCabalFile=CabalFile cabal_file
+           , uDistDir=DistDirLib distdir
+           } args ->
+        helper_main $ cabal_file : distdir : args
+getHelper proj_info qe@QueryEnv{..} = do
   withVerbosity $ withProgs (piImpl proj_info) qe $ do
-    let comp = wrapper' qeProjLoc qeDistDir proj_info
+    let comp = mkCompHelperEnv qeProjLoc qeDistDir proj_info
     let ?progs = qePrograms
         ?cprogs = qeCompPrograms
     t0 <- Clock.getTime Monotonic
@@ -635,15 +643,16 @@ getHelperExe proj_info qe@QueryEnv{..} = do
       Left rv ->
         panicIO $ "compileHelper': compiling helper failed! exit code "++ show rv
       Right exe ->
-        return exe
+        return $ Helper $ \Unit{uCabalFile, uDistDir} args ->
+          readHelper qe exe uCabalFile uDistDir args
 
-wrapper'
+mkCompHelperEnv
     :: Verbose
     => ProjLoc pt
     -> DistDir pt
     -> ProjInfo pt
     -> CompHelperEnv
-wrapper'
+mkCompHelperEnv
   projloc
   (DistDirV1 distdir)
   ProjInfo{piCabalVersion}
@@ -655,7 +664,7 @@ wrapper'
     , chePlanJson = Nothing
     , cheDistV2 = Nothing
     }
-wrapper'
+mkCompHelperEnv
   projloc
   (DistDirV2 distdir)
   ProjInfo{piImpl=ProjInfoV2{piV2Plan=plan}}
@@ -673,7 +682,7 @@ wrapper'
     chePlanJson = Just plan
     cheDistV2   = Just distdir
     PlanJson {pjCabalLibVersion=Ver pjCabalLibVersion } = plan
-wrapper'
+mkCompHelperEnv
   (ProjLocStackYaml stack_yaml)
   (DistDirStack mworkdir)
   ProjInfo
diff --git a/src/CabalHelper/Compiletime/Cabal.hs b/src/CabalHelper/Compiletime/Cabal.hs
index a61b6f6..6477b85 100644
--- a/src/CabalHelper/Compiletime/Cabal.hs
+++ b/src/CabalHelper/Compiletime/Cabal.hs
@@ -20,7 +20,7 @@ Description : Cabal library source unpacking
 License     : GPL-3
 -}
 
-{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE DeriveFunctor, CPP #-}
 
 module CabalHelper.Compiletime.Cabal where
 
@@ -36,7 +36,7 @@ import System.FilePath
 
 import CabalHelper.Compiletime.Types
 import CabalHelper.Compiletime.Process
-import CabalHelper.Shared.Common (trim, replace)
+import CabalHelper.Shared.Common (trim, replace, parseVer)
 
 type UnpackedCabalVersion = CabalVersion' (CommitId, CabalSourceDir)
 type ResolvedCabalVersion = CabalVersion' CommitId
@@ -215,3 +215,6 @@ findCabalFile pkgdir = do
         if takeFileName p == takeExtension p
           then "" -- just ".cabal" is not a valid cabal file
           else takeExtension p
+
+bultinCabalVersion :: Version
+bultinCabalVersion = parseVer VERSION_Cabal
diff --git a/src/CabalHelper/Compiletime/Data.hs b/src/CabalHelper/Compiletime/Data.hs
index 07cf2d2..14793c5 100644
--- a/src/CabalHelper/Compiletime/Data.hs
+++ b/src/CabalHelper/Compiletime/Data.hs
@@ -85,6 +85,7 @@ runtimeSources :: (String, [(FilePath, FilePath)])
 runtimeSources = $(
   let files = map (\f -> (f, ("src/CabalHelper" </> f))) $ sort $
         [ ("Runtime/Main.hs")
+        , ("Runtime/HelperMain.hs")
         , ("Runtime/Compat.hs")
         , ("Shared/Common.hs")
         , ("Shared/InterfaceTypes.hs")
diff --git a/src/CabalHelper/Runtime/HelperMain.hs b/src/CabalHelper/Runtime/HelperMain.hs
new file mode 100644
index 0000000..5c84cd2
--- /dev/null
+++ b/src/CabalHelper/Runtime/HelperMain.hs
@@ -0,0 +1,811 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015-2018  Daniel Gröber <cabal-helper@dxld.at>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation, either version 3 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE CPP, BangPatterns, RecordWildCards, RankNTypes, ViewPatterns,
+  TupleSections #-}
+
+{- # OPTIONS_GHC -Wno-missing-signatures #-}
+{- # OPTIONS_GHC -fno-warn-incomplete-patterns #-}
+
+#ifdef MIN_VERSION_Cabal
+#undef CH_MIN_VERSION_Cabal
+#define CH_MIN_VERSION_Cabal MIN_VERSION_Cabal
+#endif
+
+module CabalHelper.Runtime.HelperMain (helper_main) where
+
+import Distribution.Simple.Utils (cabalVersion)
+import Distribution.Simple.Configure
+import Distribution.Package
+  ( PackageIdentifier
+  , InstalledPackageId
+  , PackageId
+  , packageName
+  , packageVersion
+  )
+import Distribution.PackageDescription
+  ( PackageDescription
+  , GenericPackageDescription(..)
+  , Flag(..)
+  , FlagName
+  , FlagAssignment
+  , Executable(..)
+  , Library(..)
+  , TestSuite(..)
+  , Benchmark(..)
+  , BuildInfo(..)
+  , TestSuiteInterface(..)
+  , BenchmarkInterface(..)
+  , withLib
+  )
+import Distribution.PackageDescription.Configuration
+  ( flattenPackageDescription
+  )
+import Distribution.Simple.Program
+  ( requireProgram
+  , ghcProgram
+  )
+import Distribution.Simple.Program.Types
+  ( ConfiguredProgram(..)
+  )
+import Distribution.Simple.Configure
+  ( getPersistBuildConfig
+  )
+import Distribution.Simple.LocalBuildInfo
+  ( LocalBuildInfo(..)
+  , Component(..)
+  , ComponentName(..)
+  , ComponentLocalBuildInfo(..)
+  , componentBuildInfo
+  , externalPackageDeps
+  , withAllComponentsInBuildOrder
+  , withLibLBI
+  , withExeLBI
+  )
+import Distribution.Simple.GHC
+  ( componentGhcOptions
+  )
+import Distribution.Simple.Program.GHC
+  ( GhcOptions(..)
+  , renderGhcOptions
+  )
+import Distribution.Simple.Setup
+  ( ConfigFlags(..)
+  , Flag(..)
+  , fromFlagOrDefault
+  )
+import Distribution.Simple.Build
+  ( initialBuildSteps
+  )
+import Distribution.Simple.BuildPaths
+  ( autogenModuleName
+  , cppHeaderName
+  )
+import Distribution.Simple.Compiler
+  ( PackageDB(..)
+  , compilerId
+  )
+import Distribution.Compiler
+  ( CompilerId(..)
+  )
+import Distribution.ModuleName
+  ( components
+  )
+import qualified Distribution.ModuleName as C
+  ( ModuleName
+  )
+import Distribution.Text
+  ( display
+  )
+import Distribution.Verbosity
+  ( Verbosity
+  , silent
+  , deafening
+  , normal
+  )
+import Distribution.Version
+  ( Version
+  )
+
+#if CH_MIN_VERSION_Cabal(1,22,0)
+-- CPP >= 1.22
+import Distribution.Utils.NubList
+#endif
+
+#if CH_MIN_VERSION_Cabal(1,23,0)
+-- >= 1.23
+import Distribution.Simple.LocalBuildInfo
+  ( localUnitId
+  )
+#else
+-- <= 1.22
+import Distribution.Simple.LocalBuildInfo
+  ( inplacePackageId
+  )
+#endif
+
+#if CH_MIN_VERSION_Cabal(1,25,0)
+-- >=1.25
+import Distribution.PackageDescription
+  ( unFlagName
+  -- , mkFlagName
+  )
+import Distribution.Types.ForeignLib
+  ( ForeignLib(..)
+  )
+import Distribution.Types.UnqualComponentName
+  ( UnqualComponentName
+  , unUnqualComponentName
+  )
+#else
+-- <1.25
+import Distribution.PackageDescription
+  ( FlagName(FlagName)
+  )
+#endif
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+-- CPP >= 2.0
+import Distribution.Simple.LocalBuildInfo
+  ( allLibModules
+  , componentBuildDir
+  )
+import Distribution.Simple.Register
+  ( internalPackageDBPath
+  )
+import Distribution.Backpack
+  ( OpenUnitId(..),
+    OpenModule(..)
+  )
+import Distribution.ModuleName
+  ( ModuleName
+  )
+import Distribution.Types.ComponentId
+  ( unComponentId
+  )
+import Distribution.Types.ComponentLocalBuildInfo
+  ( maybeComponentInstantiatedWith
+  )
+import Distribution.Types.ModuleRenaming
+  ( ModuleRenaming(..),
+    isDefaultRenaming
+  )
+import Distribution.Types.MungedPackageId
+  ( MungedPackageId
+  )
+import Distribution.Types.UnitId
+  ( UnitId
+  , unDefUnitId
+  , unUnitId
+  )
+import Distribution.Types.UnitId
+  ( DefUnitId
+  )
+import Distribution.Utils.NubList
+  ( toNubListR
+  )
+import Distribution.Version
+  ( versionNumbers
+  , mkVersion
+  )
+import qualified Distribution.InstalledPackageInfo as Installed
+#endif
+
+#if CH_MIN_VERSION_Cabal(2,2,0)
+import Distribution.Types.GenericPackageDescription
+  ( unFlagAssignment
+  )
+#endif
+
+import Control.Applicative ((<$>), (<*>), ZipList(..))
+import Control.Arrow (first, second, (&&&))
+import Control.Monad
+import Control.Exception (catch, PatternMatchFail(..))
+import Data.List
+import qualified Data.Map.Strict as Map
+import Data.Maybe
+import Data.Monoid
+import Data.IORef
+import qualified Data.Version as DataVersion
+import System.Environment
+import System.Directory
+import System.FilePath
+import System.Exit
+import System.IO
+import System.IO.Unsafe (unsafeInterleaveIO, unsafePerformIO)
+import Text.Printf
+
+import CabalHelper.Shared.Common
+import CabalHelper.Shared.InterfaceTypes
+import CabalHelper.Runtime.Compat
+
+usage :: IO ()
+usage = do
+  prog <- getProgName
+  hPutStr stderr $ "Usage: " ++ prog ++ " " ++ usageMsg
+ where
+   usageMsg = ""
+     ++"PROJ_DIR DIST_DIR [--with-* ...]\n"
+     ++"  ( version\n"
+     ++"  | flags\n"
+     ++"  | config-flags\n"
+     ++"  | non-default-config-flags\n"
+     ++"  | write-autogen-files\n"
+     ++"  | compiler-id\n"
+     ++"  | component-info\n"
+     ++"  | print-lbi [--human]\n"
+     ++"  ) ...\n"
+
+commands :: [String]
+commands = [ "flags"
+           , "config-flags"
+           , "non-default-config-flags"
+           , "write-autogen-files"
+           , "compiler-id"
+           , "package-db-stack"
+           , "component-info"
+           , "print-lbi"
+           ]
+
+helper_main :: [String] -> IO [Maybe ChResponse]
+helper_main args = do
+  cfile : distdir : args'
+    <- case args of
+         [] -> usage >> exitFailure
+         _ -> return args
+
+  ddexists <- doesDirectoryExist distdir
+  when (not ddexists) $ do
+         errMsg $ "distdir '"++distdir++"' does not exist"
+         exitFailure
+
+  v <- maybe silent (const deafening) . lookup  "CABAL_HELPER_DEBUG" <$> getEnvironment
+  lbi <- unsafeInterleaveIO $ getPersistBuildConfig distdir
+  gpd <- unsafeInterleaveIO $ readPackageDescription v cfile
+  let pd = localPkgDescr lbi
+  let lvd = (lbi, v, distdir)
+
+  let
+      -- a =<< b $$ c   ==  (a =<< b) $$ c
+      infixr 2 $$
+      ($$) = ($)
+
+      collectCmdOptions :: [String] -> [[String]]
+      collectCmdOptions =
+          reverse . map reverse . foldl f [] . dropWhile isOpt
+       where
+         isOpt = ("--" `isPrefixOf`)
+         f [] x = [[x]]
+         f (a:as) x
+             | isOpt x = (x:a):as
+             | otherwise = [x]:(a:as)
+
+  let cmds = collectCmdOptions args'
+
+  if any (["version"] `isPrefixOf`) cmds
+    then do
+      putStrLn $
+       printf "using version %s of the Cabal library" (display cabalVersion)
+      exitSuccess
+    else return ()
+
+  flip mapM cmds $$ \x -> do
+  case x of
+    "package-id":[] ->
+      return $ Just $ ChResponseVersion $ (,)
+        (display (packageName gpd))
+        (toDataVersion (packageVersion gpd))
+
+    "flags":[] -> do
+      return $ Just $ ChResponseFlags $ sort $
+        map (flagName' &&& flagDefault) $ genPackageFlags gpd
+
+    "config-flags":[] -> do
+      return $ Just $ ChResponseFlags $ sort $
+        map (first unFlagName)
+#if CH_MIN_VERSION_Cabal(2,2,0)
+          $ unFlagAssignment $ configConfigurationsFlags
+#else
+          $ configConfigurationsFlags
+#endif
+          $ configFlags lbi
+
+    "non-default-config-flags":[] -> do
+      let flagDefinitons = genPackageFlags gpd
+          flagAssgnments =
+#if CH_MIN_VERSION_Cabal(2,2,0)
+            unFlagAssignment $ configConfigurationsFlags
+#else
+            configConfigurationsFlags
+#endif
+              $ configFlags lbi
+          nonDefaultFlags =
+              [ (flag_name, val)
+              | MkFlag {flagName=(unFlagName -> flag_name'), flagDefault=def_val} <- flagDefinitons
+              , (unFlagName -> flag_name, val) <- flagAssgnments
+              , flag_name == flag_name'
+              , val /= def_val
+              ]
+      return $ Just $ ChResponseFlags $ sort nonDefaultFlags
+
+    "write-autogen-files":[] -> do
+      initialBuildStepsForAllComponents distdir pd lbi v
+      return Nothing
+
+    "compiler-id":[] -> do
+      let CompilerId comp ver = compilerId $ compiler lbi
+      return $ Just $ ChResponseVersion $ (,) (show comp) (toDataVersion ver)
+
+    "package-db-stack":[] -> do
+      let
+          pkgDb GlobalPackageDB = ChPkgGlobal
+          pkgDb UserPackageDB   = ChPkgUser
+          pkgDb (SpecificPackageDB s) = ChPkgSpecific s
+
+      -- TODO: Setup.hs has access to the sandbox as well: ghc-mod#478
+      return $ Just $ ChResponsePkgDbs $ map pkgDb $ withPackageDB lbi
+
+    "component-info":flags -> do
+      res <- componentsInfo flags lvd lbi v distdir
+      return $ Just $ ChResponseComponentsInfo res
+
+    "print-lbi":flags ->
+      case flags of
+        ["--human"] -> print lbi >> return Nothing
+        _           -> return $ Just $ ChResponseLbi $ show lbi
+
+    cmd:_ | not (cmd `elem` commands) ->
+            errMsg ("Unknown command: " ++ cmd) >> usage >> exitFailure
+    _ ->
+            errMsg "Invalid usage!" >> usage >> exitFailure
+
+
+componentsInfo
+    :: [String]
+    -> (LocalBuildInfo, Verbosity, FilePath)
+    -> LocalBuildInfo
+    -> Verbosity
+    -> FilePath
+    -> IO (Map.Map ChComponentName ChComponentInfo)
+componentsInfo flags lvd lbi v distdir = do
+      ciGhcOptions <- componentOptions lvd True flags id
+
+      ciGhcSrcOptions <- componentOptions lvd False flags $ \opts -> mempty {
+               -- Not really needed but "unexpected package db stack: []"
+               ghcOptPackageDBs      = [GlobalPackageDB, UserPackageDB],
+
+               ghcOptCppOptions      = ghcOptCppOptions opts,
+               ghcOptCppIncludePath  = ghcOptCppIncludePath opts,
+               ghcOptCppIncludes     = ghcOptCppIncludes opts,
+               ghcOptFfiIncludes     = ghcOptFfiIncludes opts,
+               ghcOptSourcePathClear = ghcOptSourcePathClear opts,
+               ghcOptSourcePath      = ghcOptSourcePath opts
+              }
+
+      ciGhcPkgOptions <- componentOptions lvd True flags $ \opts -> mempty {
+                       ghcOptPackageDBs = ghcOptPackageDBs opts,
+                       ghcOptPackages   = ghcOptPackages opts,
+                       ghcOptHideAllPackages = ghcOptHideAllPackages opts
+                   }
+
+      ciGhcLangOptions <- componentOptions lvd False flags $ \opts -> mempty {
+                       ghcOptPackageDBs      = [GlobalPackageDB, UserPackageDB],
+
+                       ghcOptLanguage = ghcOptLanguage opts,
+                       ghcOptExtensions = ghcOptExtensions opts,
+                       ghcOptExtensionMap = ghcOptExtensionMap opts
+                   }
+
+      ciSourceDirs <- componentsMap lbi v distdir $ \_ _ bi -> return $ hsSourceDirs bi
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+      includeDirMap <- recursiveDepInfo lbi v distdir
+      ciEntrypoints <- componentsMap lbi v distdir $ \c clbi _bi -> do
+               case needsBuildOutput includeDirMap (componentUnitId clbi) of
+                 ProduceBuildOutput -> return $ componentEntrypoints c
+                 NoBuildOutput -> return seps
+                   where (_,_,seps) = recursiveIncludeDirs includeDirMap (componentUnitId clbi)
+#else
+      ciEntrypoints <- componentsMap lbi v distdir $ \c _clbi _bi ->
+               return $ componentEntrypoints c
+#endif
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+      ciNeedsBuildOutput <- componentsMap lbi v distdir $ \_c clbi _bi ->
+               return $ needsBuildOutput includeDirMap (componentUnitId clbi)
+#else
+      ciNeedsBuildOutput <- componentsMap lbi v distdir $ \_c _clbi _bi ->
+               return $ NoBuildOutput
+#endif
+
+      let comp_name = map fst ciGhcOptions
+          uiComponents = Map.fromList
+                      $ map (ciComponentName &&& id)
+                      $ getZipList
+                      $ ChComponentInfo
+                     <$> ZipList comp_name
+                     <*> ZipList (map snd ciGhcOptions)
+                     <*> ZipList (map snd ciGhcSrcOptions)
+                     <*> ZipList (map snd ciGhcPkgOptions)
+                     <*> ZipList (map snd ciGhcLangOptions)
+                     <*> ZipList (map snd ciSourceDirs)
+                     <*> ZipList (map snd ciEntrypoints)
+                     <*> ZipList (map snd ciNeedsBuildOutput)
+
+      return uiComponents
+
+
+flagName' :: Distribution.PackageDescription.Flag -> String
+flagName' = unFlagName . flagName
+
+-- getLibrary :: PackageDescription -> Library
+-- getLibrary pd = unsafePerformIO $ do
+--   lr <- newIORef (error "libraryMap: empty IORef")
+--   withLib pd (writeIORef lr)
+--   readIORef lr
+
+getLibraryClbi
+    :: PackageDescription
+    -> LocalBuildInfo
+    -> Maybe (Library, ComponentLocalBuildInfo)
+getLibraryClbi pd lbi = unsafePerformIO $ do
+  lr <- newIORef Nothing
+
+  withLibLBI pd lbi $ \ lib clbi ->
+      writeIORef lr $ Just (lib,clbi)
+
+  readIORef lr
+
+
+componentsMap :: LocalBuildInfo
+              -> Verbosity
+              -> FilePath
+              -> (   Component
+                  -> ComponentLocalBuildInfo
+                  -> BuildInfo
+                  -> IO a)
+              -> IO [(ChComponentName, a)]
+componentsMap lbi _v _distdir f = do
+    let pd = localPkgDescr lbi
+
+    lr <- newIORef []
+
+    -- withComponentsLBI is deprecated but also exists in very old versions
+    -- it's equivalent to withAllComponentsInBuildOrder in newer versions
+    withAllComponentsInBuildOrder pd lbi $ \c clbi -> do
+        let bi = componentBuildInfo c
+            name = componentNameToCh $ componentNameFromComponent c
+
+        l' <- readIORef lr
+        r <- f c clbi bi
+        writeIORef lr $ (name, r) : l'
+
+    reverse <$> readIORef lr
+
+componentOptions'
+    :: (LocalBuildInfo, Verbosity, FilePath)
+    -> Bool
+    -> [String]
+    -> (LocalBuildInfo -> Verbosity -> GhcOptions -> IO a)
+    -> (GhcOptions -> GhcOptions)
+    -> IO [(ChComponentName, a)]
+componentOptions' (lbi, v, distdir) inplaceFlag flags rf f = do
+  let pd = localPkgDescr lbi
+#if CH_MIN_VERSION_Cabal(2,0,0)
+  includeDirMap <- recursiveDepInfo lbi v distdir
+#endif
+
+  componentsMap lbi v distdir $ \c clbi bi ->
+         let
+           outdir = componentOutDir lbi c
+           (clbi', adopts) = case flags of
+                               _ | not inplaceFlag -> (clbi, mempty)
+                               ["--with-inplace"] -> (clbi, mempty)
+#if CH_MIN_VERSION_Cabal(2,0,0)
+                               [] -> removeInplaceDeps v lbi pd clbi includeDirMap
+#else
+                               [] -> removeInplaceDeps v lbi pd clbi
+#endif
+           opts = componentGhcOptions normal lbi bi clbi' outdir
+           opts' = f opts
+
+         in rf lbi v $ nubPackageFlags $ opts' `mappend` adopts
+
+componentOptions :: (LocalBuildInfo, Verbosity, FilePath)
+                 -> Bool
+                 -> [String]
+                 -> (GhcOptions -> GhcOptions)
+                 -> IO [(ChComponentName, [String])]
+componentOptions (lbi, v, distdir) inplaceFlag flags f =
+    componentOptions' (lbi, v, distdir) inplaceFlag flags renderGhcOptions' f
+
+gmModuleName :: C.ModuleName -> ChModuleName
+gmModuleName = ChModuleName . intercalate "." . components
+
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+removeInplaceDeps :: Verbosity
+                  -> LocalBuildInfo
+                  -> PackageDescription
+                  -> ComponentLocalBuildInfo
+                  -> Map.Map UnitId SubDeps
+                  -> (ComponentLocalBuildInfo, GhcOptions)
+removeInplaceDeps _v lbi pd clbi includeDirs = let
+    removeInplace c =
+      let
+        (ideps, incs) = partition (isInplaceCompInc c) (componentIncludes c)
+        hasIdeps' = not $ null ideps
+        c' = c { componentPackageDeps  = error "using deprecated field:componentPackageDeps"
+               , componentInternalDeps = []
+               , componentIncludes     = incs }
+      in (hasIdeps',c')
+
+    needsBuild = needsBuildOutput includeDirs (componentUnitId clbi)
+
+    cleanRecursiveOpts :: Component
+                       -> BuildInfo -> ComponentLocalBuildInfo -> GhcOptions
+    cleanRecursiveOpts comp libbi libclbi =
+      let
+        liboutdir = componentOutDir lbi comp
+        (_,libclbi') = removeInplace libclbi
+        (extraIncludes,extraDeps',_ems) = recursiveIncludeDirs includeDirs (componentUnitId libclbi)
+        (_,extraDeps) = partition (isInplaceCompInc libclbi) extraDeps'
+        opts = (componentGhcOptions normal lbi libbi libclbi' liboutdir) {
+                  ghcOptPackageDBs = []
+               }
+
+      in
+        opts { ghcOptSourcePath = ghcOptSourcePath opts <> toNubListR extraIncludes
+             , ghcOptPackages   = ghcOptPackages   opts <> toNubListR extraDeps }
+
+    libopts =
+      case (getLibraryClbi pd lbi, getExeClbi pd lbi) of
+        (Just (lib, libclbi),_) | hasIdeps ->
+          let
+            libbi = libBuildInfo lib
+            opts = cleanRecursiveOpts (CLib lib) libbi libclbi
+          in
+            opts { ghcOptInputModules = ghcOptInputModules opts <> (toNubListR $ allLibModules lib libclbi) }
+        (_,Just (exe,execlbi)) | hasIdeps ->
+          let
+            exebi = buildInfo exe
+          in
+            cleanRecursiveOpts (CExe exe) exebi execlbi
+        _ -> mempty
+
+    distDir = fromFlagOrDefault ("." </> "dist") (configDistPref $ configFlags lbi)
+    packageDbDir = internalPackageDBPath lbi distDir
+    (hasIdeps,clbi') = case needsBuild of
+                         NoBuildOutput -> removeInplace clbi
+                         ProduceBuildOutput -> (False, clbi)
+    libopts' = case needsBuild of
+                 NoBuildOutput -> libopts
+                 ProduceBuildOutput -> mempty { ghcOptPackageDBs = [SpecificPackageDB packageDbDir] }
+  in (clbi', libopts')
+
+getExeClbi
+    :: PackageDescription
+    -> LocalBuildInfo
+    -> Maybe (Executable, ComponentLocalBuildInfo)
+getExeClbi pd lbi = unsafePerformIO $ do
+  lr <- newIORef Nothing
+
+  withExeLBI pd lbi $ \ exe clbi ->
+      writeIORef lr $ Just (exe,clbi)
+
+  readIORef lr
+
+#else
+
+removeInplaceDeps :: Verbosity
+                  -> LocalBuildInfo
+                  -> PackageDescription
+                  -> ComponentLocalBuildInfo
+                  -> (ComponentLocalBuildInfo, GhcOptions)
+removeInplaceDeps _v lbi pd clbi = let
+    (ideps, deps) = partition (isInplaceDep lbi) (componentPackageDeps clbi)
+    hasIdeps = not $ null ideps
+    libopts =
+      case getLibraryClbi pd lbi of
+        Just (lib, libclbi) | hasIdeps ->
+          let
+            libbi = libBuildInfo lib
+            liboutdir = componentOutDir lbi (CLib lib)
+          in
+            (componentGhcOptions normal lbi libbi libclbi liboutdir) {
+                ghcOptPackageDBs = []
+            }
+        _ -> mempty
+    clbi' = clbi { componentPackageDeps = deps }
+  in (clbi', libopts)
+
+#endif
+
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+recursiveDepInfo
+    :: LocalBuildInfo
+    -> Verbosity
+    -> FilePath
+    -> IO (Map.Map UnitId SubDeps)
+recursiveDepInfo lbi v distdir = do
+  includeDirs <- componentsMap lbi v distdir $ \c clbi bi -> do
+    return (componentUnitId clbi
+           , ( SubDeps
+                { sdComponentInternalDeps = componentInternalDeps clbi
+                , sdHsSourceDirs          = hsSourceDirs bi
+                , sdComponentIncludes     = componentIncludes clbi
+                , sdComponentEntryPoints  = componentEntrypoints c})  )
+  return $ Map.fromList $ map snd includeDirs
+
+data SubDeps = SubDeps
+  { sdComponentInternalDeps :: [UnitId]
+  , sdHsSourceDirs          :: [FilePath]
+  , sdComponentIncludes     :: [(OpenUnitId, ModuleRenaming)]
+  , sdComponentEntryPoints  :: ChEntrypoint
+  }
+
+recursiveIncludeDirs :: Map.Map UnitId SubDeps
+                     -> UnitId -> ([FilePath], [(OpenUnitId, ModuleRenaming)]
+                                  , ChEntrypoint)
+recursiveIncludeDirs includeDirs unit = go ([],[],Nothing) [unit]
+  where
+    go (afp,aci,Nothing  ) [] = (afp,aci,error "recursiveIncludeDirs:no ChEntrypoint")
+    go (afp,aci,Just amep) [] = (afp,aci,amep)
+    go acc@(afp,aci,amep) (u:us) = case Map.lookup u includeDirs of
+      Nothing -> go acc us
+      Just (SubDeps us' sfp sci sep) -> go (afp++sfp,aci++sci,Just (combineEp amep sep)) (us++us')
+
+needsBuildOutput :: Map.Map UnitId SubDeps -> UnitId -> NeedsBuildOutput
+needsBuildOutput includeDirs unit = go [unit]
+  where
+    isIndef (IndefFullUnitId _ _) = True
+    isIndef _                     = False
+    go [] = NoBuildOutput
+    go (u:us) = case Map.lookup u includeDirs of
+      Nothing -> go us
+      Just (SubDeps us' _sfp sci _sep) ->
+        if any (isIndef . fst) sci
+          then ProduceBuildOutput
+          else go (us++us')
+
+-- | combineEP is used to combine the entrypoints when recursively chasing
+-- through the dependencies of a given entry point. The first parameter is the
+-- current accumulated value, and the second one is the current sub-dependency
+-- being considered. So the bias should be to preserve the type of entrypoint
+-- from the first parameter.
+combineEp :: Maybe ChEntrypoint -> ChEntrypoint -> ChEntrypoint
+combineEp Nothing e = e
+combineEp (Just ChSetupEntrypoint) e = e
+combineEp (Just (ChLibEntrypoint es1 os1 ss1))   (ChLibEntrypoint es2 os2 ss2) = (ChLibEntrypoint (nub $ es2++es1) (nub $ os2++os1) (nub $ ss2++ss1))
+combineEp _                                    e@(ChExeEntrypoint  _mi _os2)     = error $ "combineEP: cannot have a sub exe:" ++ show e
+combineEp (Just (ChExeEntrypoint  mi os1))       (ChLibEntrypoint es2 os2 ss2) = (ChExeEntrypoint mi  (nub $ os1++es2++os2++ss2))
+
+-- no, you unconditionally always wrap the result in Just, so instead of `f x = Just y; f x = Just z` do `f x = y; f x = z` and use f as `Just . f`
+
+#endif
+
+
+initialBuildStepsForAllComponents
+    :: FilePath
+    -> PackageDescription
+    -> LocalBuildInfo
+    -> Verbosity
+    -> IO ()
+initialBuildStepsForAllComponents distdir pd lbi v =
+  initialBuildSteps distdir pd lbi v
+
+
+
+#if !CH_MIN_VERSION_Cabal(1,25,0)
+-- CPP < 1.25
+unFlagName :: FlagName -> String
+unFlagName (FlagName n) = n
+-- mkFlagName n = FlagName n
+#endif
+
+toDataVersion :: Version -> DataVersion.Version
+--fromDataVersion :: DataVersion.Version -> Version
+#if CH_MIN_VERSION_Cabal(2,0,0)
+toDataVersion v = DataVersion.Version (versionNumbers v) []
+--fromDataVersion (DataVersion.Version vs _) = mkVersion vs
+#else
+toDataVersion = id
+--fromDataVersion = id
+#endif
+
+
+
+componentEntrypoints :: Component -> ChEntrypoint
+componentEntrypoints (CLib Library {..})
+    = ChLibEntrypoint
+        (map gmModuleName exposedModules)
+        (map gmModuleName $ otherModules libBuildInfo)
+#if CH_MIN_VERSION_Cabal(2,0,0)
+        (map gmModuleName signatures)
+#else
+        [] -- no signatures prior to Cabal 2.0
+#endif
+#if CH_MIN_VERSION_Cabal(2,0,0)
+componentEntrypoints (CFLib (ForeignLib{..}))
+    = ChLibEntrypoint
+        []
+        (map gmModuleName $ otherModules foreignLibBuildInfo)
+        []
+#endif
+componentEntrypoints (CExe Executable {..})
+    = ChExeEntrypoint
+        modulePath
+        (map gmModuleName $ otherModules buildInfo)
+componentEntrypoints (CTest TestSuite { testInterface = TestSuiteExeV10 _ fp, ..})
+    = ChExeEntrypoint fp (map gmModuleName $ otherModules testBuildInfo)
+componentEntrypoints (CTest TestSuite { testInterface = TestSuiteLibV09 _ mn, ..})
+    = ChLibEntrypoint [gmModuleName mn] (map gmModuleName $ otherModules testBuildInfo) []
+componentEntrypoints (CTest TestSuite {})
+    = ChLibEntrypoint [] [] []
+componentEntrypoints (CBench Benchmark { benchmarkInterface = BenchmarkExeV10 _  fp, ..})
+    = ChExeEntrypoint fp (map gmModuleName $ otherModules benchmarkBuildInfo)
+componentEntrypoints (CBench Benchmark {})
+    = ChLibEntrypoint [] [] []
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+isInplaceCompInc :: ComponentLocalBuildInfo -> (OpenUnitId, ModuleRenaming) -> Bool
+isInplaceCompInc clbi (DefiniteUnitId uid, _mr)     = unDefUnitId uid `elem` componentInternalDeps clbi
+isInplaceCompInc _clbi (IndefFullUnitId _uid _, _mmr) = False
+#endif
+
+#if CH_MIN_VERSION_Cabal(2,0,0)
+-- isInplaceDep :: LocalBuildInfo -> ComponentLocalBuildInfo -> (UnitId, MungedPackageId) -> Bool
+-- isInplaceDep lbi clbi (uid, _mpid) = uid `elem` componentInternalDeps clbi
+#else
+isInplaceDep :: LocalBuildInfo -> (UnitId, PackageId) -> Bool
+#  if CH_MIN_VERSION_Cabal(1,23,0)
+-- CPP >= 1.23
+isInplaceDep lbi (ipid, _pid) = localUnitId lbi == ipid
+#  else
+-- CPP <= 1.22
+isInplaceDep _lbi (ipid, pid) = inplacePackageId pid == ipid
+#  endif
+#endif
+
+nubPackageFlags :: GhcOptions -> GhcOptions
+#if CH_MIN_VERSION_Cabal(1,22,0)
+-- CPP >= 1.22
+-- >= 1.22 uses NubListR
+nubPackageFlags opts = opts
+#else
+nubPackageFlags opts = opts { ghcOptPackages = nub $ ghcOptPackages opts }
+#endif
+
+renderGhcOptions' :: LocalBuildInfo
+                  -> Verbosity
+                  -> GhcOptions
+                  -> IO [String]
+#if !CH_MIN_VERSION_Cabal(1,20,0)
+renderGhcOptions' lbi v opts = do
+-- CPP < 1.20
+  (ghcProg, _) <- requireProgram v ghcProgram (withPrograms lbi)
+  let Just ghcVer = programVersion ghcProg
+  return $ renderGhcOptions ghcVer opts
+#elif CH_MIN_VERSION_Cabal(1,20,0) && !CH_MIN_VERSION_Cabal(1,24,0)
+renderGhcOptions' lbi _v opts = do
+-- CPP >= 1.20 && < 1.24
+  return $ renderGhcOptions (compiler lbi) opts
+#else
+renderGhcOptions' lbi _v opts = do
+-- CPP >= 1.24
+  return $ renderGhcOptions (compiler lbi) (hostPlatform lbi) opts
+#endif
diff --git a/src/CabalHelper/Runtime/Main.hs b/src/CabalHelper/Runtime/Main.hs
index 775f6b0..71dfd9b 100644
--- a/src/CabalHelper/Runtime/Main.hs
+++ b/src/CabalHelper/Runtime/Main.hs
@@ -1,5 +1,5 @@
 -- cabal-helper: Simple interface to Cabal's configuration state
--- Copyright (C) 2015-2018  Daniel Gröber <cabal-helper@dxld.at>
+-- Copyright (C) 2018  Daniel Gröber <cabal-helper@dxld.at>
 --
 -- This program is free software: you can redistribute it and/or modify
 -- it under the terms of the GNU General Public License as published by
@@ -14,798 +14,8 @@
 -- You should have received a copy of the GNU General Public License
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-{-# LANGUAGE CPP, BangPatterns, RecordWildCards, RankNTypes, ViewPatterns,
-  TupleSections #-}
-
-{- # OPTIONS_GHC -Wno-missing-signatures #-}
-{- # OPTIONS_GHC -fno-warn-incomplete-patterns #-}
-
-#ifdef MIN_VERSION_Cabal
-#undef CH_MIN_VERSION_Cabal
-#define CH_MIN_VERSION_Cabal MIN_VERSION_Cabal
-#endif
-
-import Distribution.Simple.Utils (cabalVersion)
-import Distribution.Simple.Configure
-import Distribution.Package
-  ( PackageIdentifier
-  , InstalledPackageId
-  , PackageId
-  , packageName
-  , packageVersion
-  )
-import Distribution.PackageDescription
-  ( PackageDescription
-  , GenericPackageDescription(..)
-  , Flag(..)
-  , FlagName
-  , FlagAssignment
-  , Executable(..)
-  , Library(..)
-  , TestSuite(..)
-  , Benchmark(..)
-  , BuildInfo(..)
-  , TestSuiteInterface(..)
-  , BenchmarkInterface(..)
-  , withLib
-  )
-import Distribution.PackageDescription.Configuration
-  ( flattenPackageDescription
-  )
-import Distribution.Simple.Program
-  ( requireProgram
-  , ghcProgram
-  )
-import Distribution.Simple.Program.Types
-  ( ConfiguredProgram(..)
-  )
-import Distribution.Simple.Configure
-  ( getPersistBuildConfig
-  )
-import Distribution.Simple.LocalBuildInfo
-  ( LocalBuildInfo(..)
-  , Component(..)
-  , ComponentName(..)
-  , ComponentLocalBuildInfo(..)
-  , componentBuildInfo
-  , externalPackageDeps
-  , withAllComponentsInBuildOrder
-  , withLibLBI
-  , withExeLBI
-  )
-import Distribution.Simple.GHC
-  ( componentGhcOptions
-  )
-import Distribution.Simple.Program.GHC
-  ( GhcOptions(..)
-  , renderGhcOptions
-  )
-import Distribution.Simple.Setup
-  ( ConfigFlags(..)
-  , Flag(..)
-  , fromFlagOrDefault
-  )
-import Distribution.Simple.Build
-  ( initialBuildSteps
-  )
-import Distribution.Simple.BuildPaths
-  ( autogenModuleName
-  , cppHeaderName
-  )
-import Distribution.Simple.Compiler
-  ( PackageDB(..)
-  , compilerId
-  )
-import Distribution.Compiler
-  ( CompilerId(..)
-  )
-import Distribution.ModuleName
-  ( components
-  )
-import qualified Distribution.ModuleName as C
-  ( ModuleName
-  )
-import Distribution.Text
-  ( display
-  )
-import Distribution.Verbosity
-  ( Verbosity
-  , silent
-  , deafening
-  , normal
-  )
-import Distribution.Version
-  ( Version
-  )
-
-#if CH_MIN_VERSION_Cabal(1,22,0)
--- CPP >= 1.22
-import Distribution.Utils.NubList
-#endif
-
-#if CH_MIN_VERSION_Cabal(1,23,0)
--- >= 1.23
-import Distribution.Simple.LocalBuildInfo
-  ( localUnitId
-  )
-#else
--- <= 1.22
-import Distribution.Simple.LocalBuildInfo
-  ( inplacePackageId
-  )
-#endif
-
-#if CH_MIN_VERSION_Cabal(1,25,0)
--- >=1.25
-import Distribution.PackageDescription
-  ( unFlagName
-  -- , mkFlagName
-  )
-import Distribution.Types.ForeignLib
-  ( ForeignLib(..)
-  )
-import Distribution.Types.UnqualComponentName
-  ( UnqualComponentName
-  , unUnqualComponentName
-  )
-#else
--- <1.25
-import Distribution.PackageDescription
-  ( FlagName(FlagName)
-  )
-#endif
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
--- CPP >= 2.0
-import Distribution.Simple.LocalBuildInfo
-  ( allLibModules
-  , componentBuildDir
-  )
-import Distribution.Simple.Register
-  ( internalPackageDBPath
-  )
-import Distribution.Backpack
-  ( OpenUnitId(..),
-    OpenModule(..)
-  )
-import Distribution.ModuleName
-  ( ModuleName
-  )
-import Distribution.Types.ComponentId
-  ( unComponentId
-  )
-import Distribution.Types.ComponentLocalBuildInfo
-  ( maybeComponentInstantiatedWith
-  )
-import Distribution.Types.ModuleRenaming
-  ( ModuleRenaming(..),
-    isDefaultRenaming
-  )
-import Distribution.Types.MungedPackageId
-  ( MungedPackageId
-  )
-import Distribution.Types.UnitId
-  ( UnitId
-  , unDefUnitId
-  , unUnitId
-  )
-import Distribution.Types.UnitId
-  ( DefUnitId
-  )
-import Distribution.Utils.NubList
-  ( toNubListR
-  )
-import Distribution.Version
-  ( versionNumbers
-  , mkVersion
-  )
-import qualified Distribution.InstalledPackageInfo as Installed
-#endif
-
-#if CH_MIN_VERSION_Cabal(2,2,0)
-import Distribution.Types.GenericPackageDescription
-  ( unFlagAssignment
-  )
-#endif
-
-import Control.Applicative ((<$>), (<*>), ZipList(..))
-import Control.Arrow (first, second, (&&&))
-import Control.Monad
-import Control.Exception (catch, PatternMatchFail(..))
-import Data.List
-import qualified Data.Map.Strict as Map
-import Data.Maybe
-import Data.Monoid
-import Data.IORef
-import qualified Data.Version as DataVersion
+import CabalHelper.Runtime.HelperMain (helper_main)
 import System.Environment
-import System.Directory
-import System.FilePath
-import System.Exit
-import System.IO
-import System.IO.Unsafe (unsafeInterleaveIO, unsafePerformIO)
-import Text.Printf
-
-import CabalHelper.Shared.Common
-import CabalHelper.Shared.InterfaceTypes
-import CabalHelper.Runtime.Compat
-
-usage :: IO ()
-usage = do
-  prog <- getProgName
-  hPutStr stderr $ "Usage: " ++ prog ++ " " ++ usageMsg
- where
-   usageMsg = ""
-     ++"PROJ_DIR DIST_DIR [--with-* ...]\n"
-     ++"  ( version\n"
-     ++"  | flags\n"
-     ++"  | config-flags\n"
-     ++"  | non-default-config-flags\n"
-     ++"  | write-autogen-files\n"
-     ++"  | compiler-id\n"
-     ++"  | component-info\n"
-     ++"  | print-lbi [--human]\n"
-     ++"  ) ...\n"
-
-commands :: [String]
-commands = [ "flags"
-           , "config-flags"
-           , "non-default-config-flags"
-           , "write-autogen-files"
-           , "compiler-id"
-           , "package-db-stack"
-           , "component-info"
-           , "print-lbi"
-           ]
 
 main :: IO ()
-main = do
-  args <- getArgs
-
-  cfile : distdir : args'
-    <- case args of
-         [] -> usage >> exitFailure
-         _ -> return args
-
-  ddexists <- doesDirectoryExist distdir
-  when (not ddexists) $ do
-         errMsg $ "distdir '"++distdir++"' does not exist"
-         exitFailure
-
-  v <- maybe silent (const deafening) . lookup  "CABAL_HELPER_DEBUG" <$> getEnvironment
-  lbi <- unsafeInterleaveIO $ getPersistBuildConfig distdir
-  gpd <- unsafeInterleaveIO $ readPackageDescription v cfile
-  let pd = localPkgDescr lbi
-  let lvd = (lbi, v, distdir)
-
-  let
-      -- a =<< b $$ c   ==  (a =<< b) $$ c
-      infixr 2 $$
-      ($$) = ($)
-
-      collectCmdOptions :: [String] -> [[String]]
-      collectCmdOptions =
-          reverse . map reverse . foldl f [] . dropWhile isOpt
-       where
-         isOpt = ("--" `isPrefixOf`)
-         f [] x = [[x]]
-         f (a:as) x
-             | isOpt x = (x:a):as
-             | otherwise = [x]:(a:as)
-
-  let cmds = collectCmdOptions args'
-
-  if any (["version"] `isPrefixOf`) cmds
-    then do
-      putStrLn $
-       printf "using version %s of the Cabal library" (display cabalVersion)
-      exitSuccess
-    else return ()
-
-  print =<< flip mapM cmds $$ \x -> do
-  case x of
-    "package-id":[] ->
-      return $ Just $ ChResponseVersion $ (,)
-        (display (packageName gpd))
-        (toDataVersion (packageVersion gpd))
-
-    "flags":[] -> do
-      return $ Just $ ChResponseFlags $ sort $
-        map (flagName' &&& flagDefault) $ genPackageFlags gpd
-
-    "config-flags":[] -> do
-      return $ Just $ ChResponseFlags $ sort $
-        map (first unFlagName)
-#if CH_MIN_VERSION_Cabal(2,2,0)
-          $ unFlagAssignment $ configConfigurationsFlags
-#else
-          $ configConfigurationsFlags
-#endif
-          $ configFlags lbi
-
-    "non-default-config-flags":[] -> do
-      let flagDefinitons = genPackageFlags gpd
-          flagAssgnments =
-#if CH_MIN_VERSION_Cabal(2,2,0)
-            unFlagAssignment $ configConfigurationsFlags
-#else
-            configConfigurationsFlags
-#endif
-              $ configFlags lbi
-          nonDefaultFlags =
-              [ (flag_name, val)
-              | MkFlag {flagName=(unFlagName -> flag_name'), flagDefault=def_val} <- flagDefinitons
-              , (unFlagName -> flag_name, val) <- flagAssgnments
-              , flag_name == flag_name'
-              , val /= def_val
-              ]
-      return $ Just $ ChResponseFlags $ sort nonDefaultFlags
-
-    "write-autogen-files":[] -> do
-      initialBuildStepsForAllComponents distdir pd lbi v
-      return Nothing
-
-    "compiler-id":[] -> do
-      let CompilerId comp ver = compilerId $ compiler lbi
-      return $ Just $ ChResponseVersion $ (,) (show comp) (toDataVersion ver)
-
-    "package-db-stack":[] -> do
-      let
-          pkgDb GlobalPackageDB = ChPkgGlobal
-          pkgDb UserPackageDB   = ChPkgUser
-          pkgDb (SpecificPackageDB s) = ChPkgSpecific s
-
-      -- TODO: Setup.hs has access to the sandbox as well: ghc-mod#478
-      return $ Just $ ChResponsePkgDbs $ map pkgDb $ withPackageDB lbi
-
-    "component-info":flags -> do
-      res <- componentsInfo flags lvd lbi v distdir
-      return $ Just $ ChResponseComponentsInfo res
-
-    "print-lbi":flags ->
-      case flags of
-        ["--human"] -> print lbi >> return Nothing
-        []          -> return $ Just $ ChResponseLbi $ show lbi
-
-    cmd:_ | not (cmd `elem` commands) ->
-            errMsg ("Unknown command: " ++ cmd) >> usage >> exitFailure
-    _ ->
-            errMsg "Invalid usage!" >> usage >> exitFailure
-
-
-componentsInfo
-    :: [String]
-    -> (LocalBuildInfo, Verbosity, FilePath)
-    -> LocalBuildInfo
-    -> Verbosity
-    -> FilePath
-    -> IO (Map.Map ChComponentName ChComponentInfo)
-componentsInfo flags lvd lbi v distdir = do
-      ciGhcOptions <- componentOptions lvd True flags id
-
-      ciGhcSrcOptions <- componentOptions lvd False flags $ \opts -> mempty {
-               -- Not really needed but "unexpected package db stack: []"
-               ghcOptPackageDBs      = [GlobalPackageDB, UserPackageDB],
-
-               ghcOptCppOptions      = ghcOptCppOptions opts,
-               ghcOptCppIncludePath  = ghcOptCppIncludePath opts,
-               ghcOptCppIncludes     = ghcOptCppIncludes opts,
-               ghcOptFfiIncludes     = ghcOptFfiIncludes opts,
-               ghcOptSourcePathClear = ghcOptSourcePathClear opts,
-               ghcOptSourcePath      = ghcOptSourcePath opts
-              }
-
-      ciGhcPkgOptions <- componentOptions lvd True flags $ \opts -> mempty {
-                       ghcOptPackageDBs = ghcOptPackageDBs opts,
-                       ghcOptPackages   = ghcOptPackages opts,
-                       ghcOptHideAllPackages = ghcOptHideAllPackages opts
-                   }
-
-      ciGhcLangOptions <- componentOptions lvd False flags $ \opts -> mempty {
-                       ghcOptPackageDBs      = [GlobalPackageDB, UserPackageDB],
-
-                       ghcOptLanguage = ghcOptLanguage opts,
-                       ghcOptExtensions = ghcOptExtensions opts,
-                       ghcOptExtensionMap = ghcOptExtensionMap opts
-                   }
-
-      ciSourceDirs <- componentsMap lbi v distdir $ \_ _ bi -> return $ hsSourceDirs bi
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
-      includeDirMap <- recursiveDepInfo lbi v distdir
-      ciEntrypoints <- componentsMap lbi v distdir $ \c clbi _bi -> do
-               case needsBuildOutput includeDirMap (componentUnitId clbi) of
-                 ProduceBuildOutput -> return $ componentEntrypoints c
-                 NoBuildOutput -> return seps
-                   where (_,_,seps) = recursiveIncludeDirs includeDirMap (componentUnitId clbi)
-#else
-      ciEntrypoints <- componentsMap lbi v distdir $ \c _clbi _bi ->
-               return $ componentEntrypoints c
-#endif
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
-      ciNeedsBuildOutput <- componentsMap lbi v distdir $ \_c clbi _bi ->
-               return $ needsBuildOutput includeDirMap (componentUnitId clbi)
-#else
-      ciNeedsBuildOutput <- componentsMap lbi v distdir $ \_c _clbi _bi ->
-               return $ NoBuildOutput
-#endif
-
-      let comp_name = map fst ciGhcOptions
-          uiComponents = Map.fromList
-                      $ map (ciComponentName &&& id)
-                      $ getZipList
-                      $ ChComponentInfo
-                     <$> ZipList comp_name
-                     <*> ZipList (map snd ciGhcOptions)
-                     <*> ZipList (map snd ciGhcSrcOptions)
-                     <*> ZipList (map snd ciGhcPkgOptions)
-                     <*> ZipList (map snd ciGhcLangOptions)
-                     <*> ZipList (map snd ciSourceDirs)
-                     <*> ZipList (map snd ciEntrypoints)
-                     <*> ZipList (map snd ciNeedsBuildOutput)
-
-      return uiComponents
-
-
-flagName' :: Distribution.PackageDescription.Flag -> String
-flagName' = unFlagName . flagName
-
--- getLibrary :: PackageDescription -> Library
--- getLibrary pd = unsafePerformIO $ do
---   lr <- newIORef (error "libraryMap: empty IORef")
---   withLib pd (writeIORef lr)
---   readIORef lr
-
-getLibraryClbi
-    :: PackageDescription
-    -> LocalBuildInfo
-    -> Maybe (Library, ComponentLocalBuildInfo)
-getLibraryClbi pd lbi = unsafePerformIO $ do
-  lr <- newIORef Nothing
-
-  withLibLBI pd lbi $ \ lib clbi ->
-      writeIORef lr $ Just (lib,clbi)
-
-  readIORef lr
-
-
-componentsMap :: LocalBuildInfo
-              -> Verbosity
-              -> FilePath
-              -> (   Component
-                  -> ComponentLocalBuildInfo
-                  -> BuildInfo
-                  -> IO a)
-              -> IO [(ChComponentName, a)]
-componentsMap lbi _v _distdir f = do
-    let pd = localPkgDescr lbi
-
-    lr <- newIORef []
-
-    -- withComponentsLBI is deprecated but also exists in very old versions
-    -- it's equivalent to withAllComponentsInBuildOrder in newer versions
-    withAllComponentsInBuildOrder pd lbi $ \c clbi -> do
-        let bi = componentBuildInfo c
-            name = componentNameToCh $ componentNameFromComponent c
-
-        l' <- readIORef lr
-        r <- f c clbi bi
-        writeIORef lr $ (name, r) : l'
-
-    reverse <$> readIORef lr
-
-componentOptions'
-    :: (LocalBuildInfo, Verbosity, FilePath)
-    -> Bool
-    -> [String]
-    -> (LocalBuildInfo -> Verbosity -> GhcOptions -> IO a)
-    -> (GhcOptions -> GhcOptions)
-    -> IO [(ChComponentName, a)]
-componentOptions' (lbi, v, distdir) inplaceFlag flags rf f = do
-  let pd = localPkgDescr lbi
-#if CH_MIN_VERSION_Cabal(2,0,0)
-  includeDirMap <- recursiveDepInfo lbi v distdir
-#endif
-
-  componentsMap lbi v distdir $ \c clbi bi ->
-         let
-           outdir = componentOutDir lbi c
-           (clbi', adopts) = case flags of
-                               _ | not inplaceFlag -> (clbi, mempty)
-                               ["--with-inplace"] -> (clbi, mempty)
-#if CH_MIN_VERSION_Cabal(2,0,0)
-                               [] -> removeInplaceDeps v lbi pd clbi includeDirMap
-#else
-                               [] -> removeInplaceDeps v lbi pd clbi
-#endif
-           opts = componentGhcOptions normal lbi bi clbi' outdir
-           opts' = f opts
-
-         in rf lbi v $ nubPackageFlags $ opts' `mappend` adopts
-
-componentOptions :: (LocalBuildInfo, Verbosity, FilePath)
-                 -> Bool
-                 -> [String]
-                 -> (GhcOptions -> GhcOptions)
-                 -> IO [(ChComponentName, [String])]
-componentOptions (lbi, v, distdir) inplaceFlag flags f =
-    componentOptions' (lbi, v, distdir) inplaceFlag flags renderGhcOptions' f
-
-gmModuleName :: C.ModuleName -> ChModuleName
-gmModuleName = ChModuleName . intercalate "." . components
-
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
-removeInplaceDeps :: Verbosity
-                  -> LocalBuildInfo
-                  -> PackageDescription
-                  -> ComponentLocalBuildInfo
-                  -> Map.Map UnitId SubDeps
-                  -> (ComponentLocalBuildInfo, GhcOptions)
-removeInplaceDeps _v lbi pd clbi includeDirs = let
-    removeInplace c =
-      let
-        (ideps, incs) = partition (isInplaceCompInc c) (componentIncludes c)
-        hasIdeps' = not $ null ideps
-        c' = c { componentPackageDeps  = error "using deprecated field:componentPackageDeps"
-               , componentInternalDeps = []
-               , componentIncludes     = incs }
-      in (hasIdeps',c')
-
-    needsBuild = needsBuildOutput includeDirs (componentUnitId clbi)
-
-    cleanRecursiveOpts :: Component
-                       -> BuildInfo -> ComponentLocalBuildInfo -> GhcOptions
-    cleanRecursiveOpts comp libbi libclbi =
-      let
-        liboutdir = componentOutDir lbi comp
-        (_,libclbi') = removeInplace libclbi
-        (extraIncludes,extraDeps',_ems) = recursiveIncludeDirs includeDirs (componentUnitId libclbi)
-        (_,extraDeps) = partition (isInplaceCompInc libclbi) extraDeps'
-        opts = (componentGhcOptions normal lbi libbi libclbi' liboutdir) {
-                  ghcOptPackageDBs = []
-               }
-
-      in
-        opts { ghcOptSourcePath = ghcOptSourcePath opts <> toNubListR extraIncludes
-             , ghcOptPackages   = ghcOptPackages   opts <> toNubListR extraDeps }
-
-    libopts =
-      case (getLibraryClbi pd lbi, getExeClbi pd lbi) of
-        (Just (lib, libclbi),_) | hasIdeps ->
-          let
-            libbi = libBuildInfo lib
-            opts = cleanRecursiveOpts (CLib lib) libbi libclbi
-          in
-            opts { ghcOptInputModules = ghcOptInputModules opts <> (toNubListR $ allLibModules lib libclbi) }
-        (_,Just (exe,execlbi)) | hasIdeps ->
-          let
-            exebi = buildInfo exe
-          in
-            cleanRecursiveOpts (CExe exe) exebi execlbi
-        _ -> mempty
-
-    distDir = fromFlagOrDefault ("." </> "dist") (configDistPref $ configFlags lbi)
-    packageDbDir = internalPackageDBPath lbi distDir
-    (hasIdeps,clbi') = case needsBuild of
-                         NoBuildOutput -> removeInplace clbi
-                         ProduceBuildOutput -> (False, clbi)
-    libopts' = case needsBuild of
-                 NoBuildOutput -> libopts
-                 ProduceBuildOutput -> mempty { ghcOptPackageDBs = [SpecificPackageDB packageDbDir] }
-  in (clbi', libopts')
-
-getExeClbi
-    :: PackageDescription
-    -> LocalBuildInfo
-    -> Maybe (Executable, ComponentLocalBuildInfo)
-getExeClbi pd lbi = unsafePerformIO $ do
-  lr <- newIORef Nothing
-
-  withExeLBI pd lbi $ \ exe clbi ->
-      writeIORef lr $ Just (exe,clbi)
-
-  readIORef lr
-
-#else
-
-removeInplaceDeps :: Verbosity
-                  -> LocalBuildInfo
-                  -> PackageDescription
-                  -> ComponentLocalBuildInfo
-                  -> (ComponentLocalBuildInfo, GhcOptions)
-removeInplaceDeps _v lbi pd clbi = let
-    (ideps, deps) = partition (isInplaceDep lbi) (componentPackageDeps clbi)
-    hasIdeps = not $ null ideps
-    libopts =
-      case getLibraryClbi pd lbi of
-        Just (lib, libclbi) | hasIdeps ->
-          let
-            libbi = libBuildInfo lib
-            liboutdir = componentOutDir lbi (CLib lib)
-          in
-            (componentGhcOptions normal lbi libbi libclbi liboutdir) {
-                ghcOptPackageDBs = []
-            }
-        _ -> mempty
-    clbi' = clbi { componentPackageDeps = deps }
-  in (clbi', libopts)
-
-#endif
-
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
-recursiveDepInfo
-    :: LocalBuildInfo
-    -> Verbosity
-    -> FilePath
-    -> IO (Map.Map UnitId SubDeps)
-recursiveDepInfo lbi v distdir = do
-  includeDirs <- componentsMap lbi v distdir $ \c clbi bi -> do
-    return (componentUnitId clbi
-           , ( SubDeps
-                { sdComponentInternalDeps = componentInternalDeps clbi
-                , sdHsSourceDirs          = hsSourceDirs bi
-                , sdComponentIncludes     = componentIncludes clbi
-                , sdComponentEntryPoints  = componentEntrypoints c})  )
-  return $ Map.fromList $ map snd includeDirs
-
-data SubDeps = SubDeps
-  { sdComponentInternalDeps :: [UnitId]
-  , sdHsSourceDirs          :: [FilePath]
-  , sdComponentIncludes     :: [(OpenUnitId, ModuleRenaming)]
-  , sdComponentEntryPoints  :: ChEntrypoint
-  }
-
-recursiveIncludeDirs :: Map.Map UnitId SubDeps
-                     -> UnitId -> ([FilePath], [(OpenUnitId, ModuleRenaming)]
-                                  , ChEntrypoint)
-recursiveIncludeDirs includeDirs unit = go ([],[],Nothing) [unit]
-  where
-    go (afp,aci,Nothing  ) [] = (afp,aci,error "recursiveIncludeDirs:no ChEntrypoint")
-    go (afp,aci,Just amep) [] = (afp,aci,amep)
-    go acc@(afp,aci,amep) (u:us) = case Map.lookup u includeDirs of
-      Nothing -> go acc us
-      Just (SubDeps us' sfp sci sep) -> go (afp++sfp,aci++sci,Just (combineEp amep sep)) (us++us')
-
-needsBuildOutput :: Map.Map UnitId SubDeps -> UnitId -> NeedsBuildOutput
-needsBuildOutput includeDirs unit = go [unit]
-  where
-    isIndef (IndefFullUnitId _ _) = True
-    isIndef _                     = False
-    go [] = NoBuildOutput
-    go (u:us) = case Map.lookup u includeDirs of
-      Nothing -> go us
-      Just (SubDeps us' _sfp sci _sep) ->
-        if any (isIndef . fst) sci
-          then ProduceBuildOutput
-          else go (us++us')
-
--- | combineEP is used to combine the entrypoints when recursively chasing
--- through the dependencies of a given entry point. The first parameter is the
--- current accumulated value, and the second one is the current sub-dependency
--- being considered. So the bias should be to preserve the type of entrypoint
--- from the first parameter.
-combineEp :: Maybe ChEntrypoint -> ChEntrypoint -> ChEntrypoint
-combineEp Nothing e = e
-combineEp (Just ChSetupEntrypoint) e = e
-combineEp (Just (ChLibEntrypoint es1 os1 ss1))   (ChLibEntrypoint es2 os2 ss2) = (ChLibEntrypoint (nub $ es2++es1) (nub $ os2++os1) (nub $ ss2++ss1))
-combineEp _                                    e@(ChExeEntrypoint  _mi _os2)     = error $ "combineEP: cannot have a sub exe:" ++ show e
-combineEp (Just (ChExeEntrypoint  mi os1))       (ChLibEntrypoint es2 os2 ss2) = (ChExeEntrypoint mi  (nub $ os1++es2++os2++ss2))
-
--- no, you unconditionally always wrap the result in Just, so instead of `f x = Just y; f x = Just z` do `f x = y; f x = z` and use f as `Just . f`
-
-#endif
-
-
-initialBuildStepsForAllComponents
-    :: FilePath
-    -> PackageDescription
-    -> LocalBuildInfo
-    -> Verbosity
-    -> IO ()
-initialBuildStepsForAllComponents distdir pd lbi v =
-  initialBuildSteps distdir pd lbi v
-
-
-
-#if !CH_MIN_VERSION_Cabal(1,25,0)
--- CPP < 1.25
-unFlagName :: FlagName -> String
-unFlagName (FlagName n) = n
--- mkFlagName n = FlagName n
-#endif
-
-toDataVersion :: Version -> DataVersion.Version
---fromDataVersion :: DataVersion.Version -> Version
-#if CH_MIN_VERSION_Cabal(2,0,0)
-toDataVersion v = DataVersion.Version (versionNumbers v) []
---fromDataVersion (DataVersion.Version vs _) = mkVersion vs
-#else
-toDataVersion = id
---fromDataVersion = id
-#endif
-
-
-
-componentEntrypoints :: Component -> ChEntrypoint
-componentEntrypoints (CLib Library {..})
-    = ChLibEntrypoint
-        (map gmModuleName exposedModules)
-        (map gmModuleName $ otherModules libBuildInfo)
-#if CH_MIN_VERSION_Cabal(2,0,0)
-        (map gmModuleName signatures)
-#else
-        [] -- no signatures prior to Cabal 2.0
-#endif
-#if CH_MIN_VERSION_Cabal(2,0,0)
-componentEntrypoints (CFLib (ForeignLib{..}))
-    = ChLibEntrypoint
-        []
-        (map gmModuleName $ otherModules foreignLibBuildInfo)
-        []
-#endif
-componentEntrypoints (CExe Executable {..})
-    = ChExeEntrypoint
-        modulePath
-        (map gmModuleName $ otherModules buildInfo)
-componentEntrypoints (CTest TestSuite { testInterface = TestSuiteExeV10 _ fp, ..})
-    = ChExeEntrypoint fp (map gmModuleName $ otherModules testBuildInfo)
-componentEntrypoints (CTest TestSuite { testInterface = TestSuiteLibV09 _ mn, ..})
-    = ChLibEntrypoint [gmModuleName mn] (map gmModuleName $ otherModules testBuildInfo) []
-componentEntrypoints (CTest TestSuite {})
-    = ChLibEntrypoint [] [] []
-componentEntrypoints (CBench Benchmark { benchmarkInterface = BenchmarkExeV10 _  fp, ..})
-    = ChExeEntrypoint fp (map gmModuleName $ otherModules benchmarkBuildInfo)
-componentEntrypoints (CBench Benchmark {})
-    = ChLibEntrypoint [] [] []
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
-isInplaceCompInc :: ComponentLocalBuildInfo -> (OpenUnitId, ModuleRenaming) -> Bool
-isInplaceCompInc clbi (DefiniteUnitId uid, _mr)     = unDefUnitId uid `elem` componentInternalDeps clbi
-isInplaceCompInc _clbi (IndefFullUnitId _uid _, _mmr) = False
-#endif
-
-#if CH_MIN_VERSION_Cabal(2,0,0)
--- isInplaceDep :: LocalBuildInfo -> ComponentLocalBuildInfo -> (UnitId, MungedPackageId) -> Bool
--- isInplaceDep lbi clbi (uid, _mpid) = uid `elem` componentInternalDeps clbi
-#else
-isInplaceDep :: LocalBuildInfo -> (UnitId, PackageId) -> Bool
-#  if CH_MIN_VERSION_Cabal(1,23,0)
--- CPP >= 1.23
-isInplaceDep lbi (ipid, _pid) = localUnitId lbi == ipid
-#  else
--- CPP <= 1.22
-isInplaceDep _lbi (ipid, pid) = inplacePackageId pid == ipid
-#  endif
-#endif
-
-nubPackageFlags :: GhcOptions -> GhcOptions
-#if CH_MIN_VERSION_Cabal(1,22,0)
--- CPP >= 1.22
--- >= 1.22 uses NubListR
-nubPackageFlags opts = opts
-#else
-nubPackageFlags opts = opts { ghcOptPackages = nub $ ghcOptPackages opts }
-#endif
-
-renderGhcOptions' :: LocalBuildInfo
-                  -> Verbosity
-                  -> GhcOptions
-                  -> IO [String]
-#if !CH_MIN_VERSION_Cabal(1,20,0)
-renderGhcOptions' lbi v opts = do
--- CPP < 1.20
-  (ghcProg, _) <- requireProgram v ghcProgram (withPrograms lbi)
-  let Just ghcVer = programVersion ghcProg
-  return $ renderGhcOptions ghcVer opts
-#elif CH_MIN_VERSION_Cabal(1,20,0) && !CH_MIN_VERSION_Cabal(1,24,0)
-renderGhcOptions' lbi _v opts = do
--- CPP >= 1.20 && < 1.24
-  return $ renderGhcOptions (compiler lbi) opts
-#else
-renderGhcOptions' lbi _v opts = do
--- CPP >= 1.24
-  return $ renderGhcOptions (compiler lbi) (hostPlatform lbi) opts
-#endif
+main = getArgs >>= helper_main >>= print