Initial commit

11 files changed, 2067 insertions, 0 deletions

diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..d3fc908
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,19 @@
+language: haskell
+ghc:
+  - 7.4
+  - 7.6
+  - 7.8
+
+install:
+  - cabal update
+  - echo $PATH
+  - which cabal
+  - cabal install -j --only-dependencies --enable-tests
+
+script:
+  - touch ChangeLog # Create ChangeLog if we're not on the release branch
+  - cabal check
+  - if [ -n "$(ghc --version | awk '{ print $8 }' | sed -n '/^7.8/p')" ]; then export WERROR="--ghc-option=-Werror"; fi
+  - cabal configure --enable-tests $WERROR
+  - cabal build
+#  - cabal test
diff --git a/CabalHelper/Common.hs b/CabalHelper/Common.hs
new file mode 100644
index 0000000..2e8ff6a
--- /dev/null
+++ b/CabalHelper/Common.hs
@@ -0,0 +1,98 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE DeriveDataTypeable, OverloadedStrings #-}
+module CabalHelper.Common where
+
+import Control.Applicative
+import Control.Exception as E
+import Control.Monad
+import Data.List
+import Data.Maybe
+import Data.Version
+import Data.Typeable
+import Data.ByteString (ByteString)
+import qualified Data.ByteString as BS
+import qualified Data.ByteString.Char8 as BS8
+import System.Environment
+import System.IO
+import System.Exit
+import Text.ParserCombinators.ReadP
+
+data Panic = Panic String deriving (Typeable, Show)
+instance Exception Panic
+
+panic :: String -> a
+panic msg = throw $ Panic msg
+
+handlePanic :: IO a -> IO a
+handlePanic action =
+    action `E.catch` \(Panic msg) -> errMsg msg >> exitFailure
+
+errMsg :: String -> IO ()
+errMsg str = do
+  prog <- getProgName
+  hPutStrLn stderr $ prog ++ ": " ++ str
+
+align :: String -> String -> String -> String
+align n an str = let
+    h:rest = lines str
+    [hm]   = match n h
+    rest'  = [ move (hm - rm) r | r <- rest, rm <- match an r]
+    in
+      unlines (h:rest')
+ where
+   match p str' = maybeToList $
+     fst <$> find ((p `isPrefixOf`) . snd) ([0..] `zip` tails str')
+   move i str' | i > 0  = replicate i ' ' ++ str'
+   move i str' = drop i str'
+
+
+-- | @getCabalConfigHeader "dist/setup-config"@ returns the cabal version and
+-- compiler version
+getCabalConfigHeader :: FilePath -> IO (Maybe (Version, Version))
+getCabalConfigHeader file = bracket (openFile file ReadMode) hClose $ \h -> do
+  parseHeader <$> BS.hGetLine h
+
+parseHeader :: ByteString -> Maybe (Version, Version)
+parseHeader header = case BS8.words header of
+  ["Saved", "package", "config", "for", _pkgId ,
+   "written", "by", cabalId,
+   "using", compId]
+    -> liftM2 (,) (ver cabalId) (ver compId)
+  _ -> Nothing
+ where
+   ver i = snd <$> parsePkgId i
+
+parsePkgId :: ByteString -> Maybe (ByteString, Version)
+parsePkgId bs =
+    case BS8.split '-' bs of
+      [pkg, vers] -> Just (pkg, parseVer $ BS8.unpack vers)
+      _ -> Nothing
+
+parseVer :: String -> Version
+parseVer vers = runReadP parseVersion vers
+
+-- majorVer :: Version -> Version
+-- majorVer (Version b _) = Version (take 2 b) []
+
+-- sameMajorVersion :: Version -> Version -> Bool
+-- sameMajorVersion a b = majorVer a == majorVer b
+
+runReadP :: ReadP t -> String -> t
+runReadP p i = case filter ((=="") . snd) $ readP_to_S p i of
+                 (a,""):[] -> a
+                 _ -> error $ "Error parsing: " ++ show i
diff --git a/CabalHelper/Data.hs b/CabalHelper/Data.hs
new file mode 100644
index 0000000..28d0859
--- /dev/null
+++ b/CabalHelper/Data.hs
@@ -0,0 +1,39 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE TemplateHaskell #-}
+module CabalHelper.Data where
+
+import Control.Monad
+import Data.Functor
+import Language.Haskell.TH
+import System.FilePath
+import System.Directory
+import System.IO.Temp
+
+withHelperSources :: (FilePath -> IO a) -> IO a
+withHelperSources action = withSystemTempDirectory "caba-helper" $ \dir -> do
+    let chdir = dir </> "CabalHelper"
+    createDirectory chdir
+    forM_ sourceFiles $ \(fn, src) -> writeFile (chdir </> fn) src
+    action dir
+
+sourceFiles :: [(FilePath, String)]
+sourceFiles =
+  [ ("Main.hs",   $(LitE . StringL <$> runIO (readFile "CabalHelper/Main.hs")))
+  , ("Common.hs", $(LitE . StringL <$> runIO (readFile "CabalHelper/Common.hs")))
+  , ("Types.hs",  $(LitE . StringL <$> runIO (readFile "CabalHelper/Types.hs")))
+  ]
diff --git a/CabalHelper/GuessGhc.hs b/CabalHelper/GuessGhc.hs
new file mode 100644
index 0000000..0827456
--- /dev/null
+++ b/CabalHelper/GuessGhc.hs
@@ -0,0 +1,83 @@
+module CabalHelper.GuessGhc (guessToolFromGhcPath) where
+
+import Data.Maybe
+import Data.Char
+import Distribution.Simple.BuildPaths
+import System.Directory
+import System.FilePath
+
+-- Copyright (c) 2003-2014, Isaac Jones, Simon Marlow, Martin Sjögren,
+--                          Bjorn Bringert, Krasimir Angelov,
+--                          Malcolm Wallace, Ross Patterson, Ian Lynagh,
+--                          Duncan Coutts, Thomas Schilling,
+--                          Johan Tibell, Mikhail Glushenkov
+-- All rights reserved.
+
+-- Redistribution and use in source and binary forms, with or without
+-- modification, are permitted provided that the following conditions are
+-- met:
+
+--     * Redistributions of source code must retain the above copyright
+--       notice, this list of conditions and the following disclaimer.
+
+--     * Redistributions in binary form must reproduce the above
+--       copyright notice, this list of conditions and the following
+--       disclaimer in the documentation and/or other materials provided
+--       with the distribution.
+
+--     * Neither the name of Isaac Jones nor the names of other
+--       contributors may be used to endorse or promote products derived
+--       from this software without specific prior written permission.
+
+-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+-- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+-- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+-- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+-- OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+-- SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+-- LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+-- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+-- THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+-- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+guessToolFromGhcPath :: FilePath -- ^ Tool name
+                     -> FilePath -- ^ GHC exe path
+                     -> IO (Maybe FilePath)
+guessToolFromGhcPath toolname ghcPath
+  = do let
+           path              = ghcPath
+           dir               = takeDirectory path
+           versionSuffix     = takeVersionSuffix (dropExeExtension path)
+           guessNormal       = dir </> toolname <.> exeExtension
+           guessGhcVersioned = dir </> (toolname ++ "-ghc" ++ versionSuffix)
+                               <.> exeExtension
+           guessVersioned    = dir </> (toolname ++ versionSuffix)
+                               <.> exeExtension
+           guesses | null versionSuffix = [guessNormal]
+                   | otherwise          = [guessGhcVersioned,
+                                           guessVersioned,
+                                           guessNormal]
+       exists <- mapM doesFileExist guesses
+       return $ listToMaybe [ file | (file, True) <- zip guesses exists ]
+
+  where takeVersionSuffix :: FilePath -> String
+        takeVersionSuffix = takeWhileEndLE isSuffixChar
+
+        isSuffixChar :: Char -> Bool
+        isSuffixChar c = isDigit c || c == '.' || c == '-'
+
+        dropExeExtension :: FilePath -> FilePath
+        dropExeExtension filepath =
+          case splitExtension filepath of
+            (filepath', extension) | extension == exeExtension -> filepath'
+                                   | otherwise                 -> filepath
+
+-- | @takeWhileEndLE p@ is equivalent to @reverse . takeWhile p . reverse@, but
+-- is usually faster (as well as being easier to read).
+takeWhileEndLE :: (a -> Bool) -> [a] -> [a]
+takeWhileEndLE p = fst . foldr go ([], False)
+  where
+    go x (rest, done)
+      | not done && p x = (x:rest, False)
+      | otherwise = (rest, True)
diff --git a/CabalHelper/Main.hs b/CabalHelper/Main.hs
new file mode 100644
index 0000000..777ac7a
--- /dev/null
+++ b/CabalHelper/Main.hs
@@ -0,0 +1,344 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE CPP, BangPatterns, RecordWildCards #-}
+{-# OPTIONS_GHC -fno-warn-deprecations #-}
+import Distribution.Simple.Utils (cabalVersion)
+import Distribution.Simple.Configure
+
+import Distribution.Package (PackageIdentifier, InstalledPackageId, PackageId)
+import Distribution.PackageDescription (PackageDescription,
+                                        FlagAssignment,
+                                        Executable(..),
+                                        Library(..),
+                                        TestSuite(..),
+                                        Benchmark(..),
+                                        BuildInfo(..),
+                                        TestSuiteInterface(..),
+                                        BenchmarkInterface(..),
+                                        withLib)
+import Distribution.PackageDescription.Parse (readPackageDescription)
+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,
+                                           withComponentsLBI,
+                                           inplacePackageId)
+
+import Distribution.Simple.GHC (componentGhcOptions)
+import Distribution.Simple.Program.GHC (GhcOptions(..), renderGhcOptions)
+
+import Distribution.Simple.Setup (ConfigFlags(..),Flag(..))
+import Distribution.Simple.Build (initialBuildSteps)
+import Distribution.Simple.BuildPaths (autogenModuleName, cppHeaderName, exeExtension)
+import Distribution.Simple.Compiler (PackageDB(..))
+
+import Distribution.ModuleName (components)
+import qualified Distribution.ModuleName as C (ModuleName)
+import Distribution.Text (display)
+import Distribution.Verbosity (Verbosity, silent, deafening)
+
+#if CABAL_MAJOR == 1 && CABAL_MINOR >= 22
+import Distribution.Utils.NubList
+#endif
+
+import Control.Applicative ((<$>))
+import Control.Monad
+import Control.Exception (catch, PatternMatchFail(..))
+import Data.List
+import Data.Maybe
+import Data.Monoid
+import Data.IORef
+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.Common
+import CabalHelper.Types
+
+usage = do
+  prog <- getProgName
+  hPutStr stderr $ align "(" "|" ("Usage: " ++ prog ++ " " ++ usageMsg)
+ where
+   usageMsg = ""
+     ++"DIST_DIR ( version\n"
+     ++"         | print-lbi\n"
+     ++"         | write-autogen-files\n"
+     ++"         | ghc-options [--with-inplace]\n"
+     ++"         | ghc-src-options [--with-inplace]\n"
+     ++"         | ghc-pkg-options [--with-inplace]\n"
+     ++"         | entrypoints\n"
+     ++"         | source-dirs\n"
+     ++"         ) ...\n"
+
+commands :: [String]
+commands = [ "print-bli"
+           , "write-autogen-files"
+           , "component-from-file"
+           , "ghc-options"
+           , "ghc-src-options"
+           , "ghc-pkg-options"
+           , "entrypoints"
+           , "source-dirs"]
+
+main :: IO ()
+main = do
+  args <- getArgs
+
+  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  "GHC_MOD_DEBUG" <$> getEnvironment
+  lbi <- unsafeInterleaveIO $ getPersistBuildConfig distdir
+  let pd = localPkgDescr lbi
+
+  let
+      -- a =<< b $$ c   ==  (a =<< b) $$ c
+      -- a <$$> b $$ c  ==  a <$$> (b $$ c)
+      infixr 2 $$
+      ($$) = ($)
+      infixr 1 <$$>
+      (<$$>) = (<$>)
+
+      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 $$ \cmd -> do
+  case cmd of
+    "write-autogen-files":[] -> do
+      let pd = localPkgDescr lbi
+       -- calls writeAutogenFiles
+      initialBuildSteps distdir pd lbi v
+      return Nothing
+
+    "ghc-options":flags ->
+      Just . GmCabalHelperStrings <$$> componentsMap lbi v distdir $$
+      \c clbi bi -> let
+           outdir = componentOutDir lbi c
+           (clbi', adopts) = case flags of
+                               ["--with-inplace"] -> (clbi, mempty)
+                               [] -> removeInplaceDeps pd clbi
+           opts = componentGhcOptions v lbi bi clbi' outdir
+           in
+              renderGhcOptions' lbi v $ opts `mappend` adopts
+
+    "ghc-src-options":flags ->
+      Just . GmCabalHelperStrings <$$> componentsMap lbi v distdir $$
+      \c clbi bi -> let
+           outdir = componentOutDir lbi c
+           (clbi', adopts) = case flags of
+                               ["--with-inplace"] -> (clbi, mempty)
+                               [] -> removeInplaceDeps pd clbi
+           opts = componentGhcOptions v lbi bi clbi' outdir
+           comp = compiler lbi
+
+           opts' = mempty {
+               -- Not really needed but "unexpected package db stack: []"
+               ghcOptPackageDBs      = [GlobalPackageDB],
+               ghcOptCppOptions      = ghcOptCppOptions opts,
+               ghcOptCppIncludePath  = ghcOptCppIncludePath opts,
+               ghcOptCppIncludes     = ghcOptCppIncludes opts,
+               ghcOptFfiIncludes     = ghcOptFfiIncludes opts,
+               ghcOptSourcePathClear = ghcOptSourcePathClear opts,
+               ghcOptSourcePath      = ghcOptSourcePath opts
+              }
+            in
+              renderGhcOptions' lbi v $ opts `mappend` adopts
+
+    "ghc-pkg-options":flags ->
+      Just . GmCabalHelperStrings <$$> componentsMap lbi v distdir $$
+      \c clbi bi -> let
+           comp = compiler lbi
+           outdir = componentOutDir lbi c
+           (clbi', adopts) = case flags of
+                               ["--with-inplace"] -> (clbi, mempty)
+                               [] -> removeInplaceDeps pd clbi
+           opts = componentGhcOptions v lbi bi clbi' outdir
+
+           opts' = mempty {
+                       ghcOptPackageDBs = ghcOptPackageDBs opts,
+                       ghcOptPackages   = ghcOptPackages opts,
+                       ghcOptHideAllPackages = ghcOptHideAllPackages opts
+                   }
+           in
+             renderGhcOptions' lbi v $ opts' `mappend` adopts
+
+    "entrypoints":[] -> do
+      eps <- componentsMap lbi v distdir $ \c clbi bi ->
+               return $ componentEntrypoints c
+      -- MUST append Setup component at the end otherwise CabalHelper gets
+      -- confused
+      let eps' = eps ++ [(GmSetupHsName, Right [GmModuleName "Setup"])]
+      return $ Just $ GmCabalHelperEntrypoints eps'
+
+    "source-dirs":[] ->
+      Just . GmCabalHelperStrings <$$> componentsMap lbi v distdir $$
+      \c clbi bi -> return $ hsSourceDirs bi
+
+    "print-lbi":[] ->
+      return $ Just $ GmCabalHelperLbi $ show lbi
+
+    cmd:_ | not (cmd `elem` commands) ->
+            errMsg ("Unknown command: " ++ cmd) >> usage >> exitFailure
+    _ ->
+            errMsg "Invalid usage!" >> usage >> exitFailure
+
+
+getLibrary :: PackageDescription -> Library
+getLibrary pd = unsafePerformIO $ do
+  lr <- newIORef (error "libraryMap: empty IORef")
+  withLib pd (writeIORef lr)
+  readIORef lr
+
+componentsMap :: LocalBuildInfo
+              -> Verbosity
+              -> FilePath
+              -> (   Component
+                  -> ComponentLocalBuildInfo
+                  -> BuildInfo
+                  -> IO a)
+              -> IO [(GmComponentName, a)]
+componentsMap lbi v distdir f = do
+    let pd = localPkgDescr lbi
+
+    lr <- newIORef []
+
+    withComponentsLBI pd lbi $ \c clbi -> do
+        let bi = componentBuildInfo c
+            name = componentNameFromComponent c
+
+        l' <- readIORef lr
+        r <- f c clbi bi
+        writeIORef lr $ (componentNameToGm name, r):l'
+    reverse <$> readIORef lr
+
+componentNameToGm CLibName = GmLibName
+componentNameToGm (CExeName n) = GmExeName n
+componentNameToGm (CTestName n) = GmTestName n
+componentNameToGm (CBenchName n) = GmBenchName n
+
+componentNameFromComponent (CLib Library {}) = CLibName
+componentNameFromComponent (CExe Executable {..}) = CExeName exeName
+componentNameFromComponent (CTest TestSuite {..}) = CTestName testName
+componentNameFromComponent (CBench Benchmark {..}) = CBenchName benchmarkName
+
+componentOutDir lbi (CLib Library {..})= buildDir lbi
+componentOutDir lbi (CExe Executable {..})= exeOutDir lbi exeName
+componentOutDir lbi (CTest TestSuite { testInterface = TestSuiteExeV10 _ _, ..}) =
+    exeOutDir lbi testName
+componentOutDir lbi (CTest TestSuite { testInterface = TestSuiteLibV09 _ _, ..}) =
+    exeOutDir lbi (testName ++ "Stub")
+componentOutDir lbi (CBench Benchmark { benchmarkInterface = BenchmarkExeV10 _ _, ..})=
+    exeOutDir lbi benchmarkName
+
+gmModuleName :: C.ModuleName -> GmModuleName
+gmModuleName = GmModuleName . intercalate "." . components
+
+componentEntrypoints :: Component -> Either FilePath [GmModuleName]
+componentEntrypoints (CLib Library {..})
+    = Right $ map gmModuleName $ exposedModules ++ (otherModules libBuildInfo)
+componentEntrypoints (CExe Executable {..})
+    = Left modulePath
+componentEntrypoints (CTest TestSuite { testInterface = TestSuiteExeV10 _ fp })
+    = Left fp
+componentEntrypoints (CTest TestSuite { testInterface = TestSuiteLibV09 _ mn })
+    = Right [gmModuleName mn]
+componentEntrypoints (CTest TestSuite {})
+    = Right []
+componentEntrypoints (CBench Benchmark { benchmarkInterface = BenchmarkExeV10 _  fp})
+    = Left fp
+componentEntrypoints (CBench Benchmark {})
+    = Left []
+
+exeOutDir :: LocalBuildInfo -> String -> FilePath
+exeOutDir lbi exeName =
+  ----- Copied from Distribution/Simple/GHC.hs:buildOrReplExe
+  -- exeNameReal, the name that GHC really uses (with .exe on Windows)
+  let exeNameReal = exeName <.>
+                    (if takeExtension exeName /= ('.':exeExtension)
+                       then exeExtension
+                       else "")
+
+      targetDir = (buildDir lbi) </> exeName
+  in targetDir
+
+
+removeInplaceDeps :: PackageDescription
+                  -> ComponentLocalBuildInfo
+                  -> (ComponentLocalBuildInfo, GhcOptions)
+removeInplaceDeps pd clbi = let
+    (ideps, deps) = partition isInplaceDep (componentPackageDeps clbi)
+    hasIdeps = not $ null ideps
+    clbi' = clbi { componentPackageDeps = deps }
+    lib = getLibrary pd
+    src_dirs = hsSourceDirs (libBuildInfo lib)
+    adopts = mempty {
+               ghcOptSourcePath      =
+#if CABAL_MAJOR == 1 && CABAL_MINOR >= 22
+                   toNubListR src_dirs
+#else
+                   src_dirs
+#endif
+
+             }
+
+  in (clbi', if hasIdeps then adopts else mempty)
+
+ where
+   isInplaceDep :: (InstalledPackageId, PackageId) -> Bool
+   isInplaceDep (ipid, pid) = inplacePackageId pid == ipid
+
+renderGhcOptions' lbi v opts = do
+#if CABAL_MAJOR == 1 && CABAL_MINOR < 20
+  (ghcProg, _) <- requireProgram v ghcProgram (withPrograms lbi)
+  let Just ghcVer = programVersion ghcProg
+  return $ renderGhcOptions ghcVer opts
+#else
+  return $ renderGhcOptions (compiler lbi) opts
+#endif
diff --git a/CabalHelper/Types.hs b/CabalHelper/Types.hs
new file mode 100644
index 0000000..85cf2d2
--- /dev/null
+++ b/CabalHelper/Types.hs
@@ -0,0 +1,40 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+module CabalHelper.Types where
+
+newtype ChModuleName = ChModuleName String
+    deriving (Eq, Ord, Read, Show)
+
+data ChComponentName = ChSetupHsName
+                     | ChLibName
+                     | ChExeName String
+                     | ChTestName String
+                     | ChBenchName String
+  deriving (Eq, Ord, Read, Show)
+
+data Response
+    = ResponseStrings    [(ChComponentName, [String])]
+    | ResponseEntrypoints [(ChComponentName, ChEntrypoint)]
+    | ResponseLbi String
+  deriving (Eq, Ord, Read, Show)
+
+data ChEntrypoint = ChExeEntrypoint { chMainIs         :: FilePath
+                                    , chOtherModules   :: [ChModuleName]
+                                    }
+                  | ChLibentrypoint { chExposedModules :: [ChModuleName]
+                                    , chOtherModules   :: [ChModuleName]
+                                    } deriving (Eq, Ord, Read, Show)
diff --git a/CabalHelper/Wrapper.hs b/CabalHelper/Wrapper.hs
new file mode 100644
index 0000000..6ba933d
--- /dev/null
+++ b/CabalHelper/Wrapper.hs
@@ -0,0 +1,368 @@
+-- cabal-helper: Simple interface to Cabal's configuration state
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE RecordWildCards, FlexibleContexts #-}
+module Main where
+
+import Control.Applicative
+import Control.Arrow
+import Control.Exception as E
+import Control.Monad
+import Control.Monad.Trans.Maybe
+import Control.Monad.IO.Class
+import Data.Char
+import Data.List
+import Data.Maybe
+import Data.String
+import Data.Version
+import Text.Printf
+import System.Console.GetOpt
+import System.Environment
+import System.Directory
+import System.FilePath
+import System.Process
+import System.Exit
+import System.IO
+
+import Distribution.System (buildPlatform)
+import Distribution.Text (display)
+
+import Paths_cabal_helper (version)
+import CabalHelper.Data
+import CabalHelper.Common
+import CabalHelper.GuessGhc
+
+usage :: IO ()
+usage = do
+  prog <- getProgName
+  hPutStr stderr $ align "(" "|" ("Usage: " ++ prog ++ " " ++ usageMsg)
+ where
+   usageMsg = "\
+\( print-appdatadir\n\
+\| print-build-platform\n\
+\| DIST_DIR ( print-exe | [CABAL_HELPER_ARGS...] ) )\n"
+
+data Options = Options {
+          ghcProgram    :: FilePath
+        , ghcPkgProgram :: FilePath
+        , cabalProgram  :: FilePath
+}
+
+defaultOptions :: Options
+defaultOptions = Options "ghc" "ghc-pkg" "cabal"
+
+globalArgSpec :: [OptDescr (Options -> Options)]
+globalArgSpec =
+      [ option "" ["with-ghc"] "GHC executable to use" $
+              reqArg "PROG" $ \p o -> o { ghcProgram = p }
+
+      , option "" ["with-ghc-pkg"] "ghc-pkg executable to use (only needed when guessing from GHC path fails)" $
+              reqArg "PROG" $ \p o -> o { ghcPkgProgram = p }
+
+      , option "" ["with-cabal"] "cabal-install executable to use" $
+               reqArg "PROG" $ \p o -> o { cabalProgram = p }
+      ]
+ where
+   option :: [Char] -> [String] -> String -> ArgDescr a -> OptDescr a
+   option s l udsc dsc = Option s l dsc udsc
+
+   reqArg :: String -> (String -> a) -> ArgDescr a
+   reqArg udsc dsc = ReqArg dsc udsc
+
+parseCommandArgs :: Options -> [String] -> (Options, [String])
+parseCommandArgs opts argv
+    = case getOpt Permute globalArgSpec argv of
+        (o,r,[])   -> (foldr id opts o, r)
+        (_,_,errs) ->
+            panic $ "Parsing command options failed: " ++ concat errs
+
+guessProgramPaths :: Options -> IO Options
+guessProgramPaths opts = do
+    if not (same ghcProgram opts dopts) && same ghcPkgProgram opts dopts
+       then do
+         mghcPkg <- guessToolFromGhcPath "ghc-pkg" (ghcProgram opts)
+         return opts {
+           ghcPkgProgram = fromMaybe (ghcPkgProgram opts) mghcPkg
+         }
+       else return opts
+ where
+   same f o o'  = f o == f o'
+   dopts = defaultOptions
+
+main :: IO ()
+main = handlePanic $ do
+  (opts', args) <- parseCommandArgs defaultOptions <$> getArgs
+  opts <- guessProgramPaths opts'
+  case args of
+    [] -> usage
+    "--help":[] -> usage
+    "print-appdatadir":[] -> putStrLn =<< appDataDir
+    "print-build-platform":[] -> putStrLn $ display buildPlatform
+    distdir:args' -> do
+      cfgf <- canonicalizePath (distdir </> "setup-config")
+      mhdr <- getCabalConfigHeader cfgf
+      case mhdr of
+        Nothing -> panic $ printf "\
+\Could not read Cabal's persistent setup configuration header\n\
+\- Check first line of: %s\n\
+\- Maybe try: $ cabal configure" cfgf
+
+        Just (hdrCabalVersion, _hdrCompilerVersion) -> do
+          eexe <- compileHelper opts hdrCabalVersion distdir
+          case eexe of
+              Left e -> exitWith e
+              Right exe ->
+                case args' of
+                  "print-exe":_ -> putStrLn exe
+                  _ -> do
+                    (_,_,_,h) <- createProcess $ proc exe args
+                    exitWith =<< waitForProcess h
+
+appDataDir :: IO FilePath
+appDataDir = (</> "cabal-helper") <$> getAppUserDataDirectory "ghc-mod"
+
+compileHelper :: Options -> Version -> FilePath -> IO (Either ExitCode FilePath)
+compileHelper opts cabalVer distdir = withHelperSources $ \chdir -> do
+  run [ Right <$> MaybeT (cachedExe cabalVer)
+      , compileGlobal chdir
+      , cachedCabalPkg chdir
+      , compileCabalSource chdir
+      , MaybeT (Just <$> compileSandbox chdir)
+      ]
+
+ where
+   run actions = fromJust <$> runMaybeT (msum actions)
+
+   -- | Check if this version is globally available
+   compileGlobal :: FilePath -> MaybeT IO (Either ExitCode FilePath)
+   compileGlobal chdir = do
+       _ <- MaybeT $ find (== cabalVer) <$> listCabalVersions opts
+       liftIO $ compileWithPkg chdir Nothing
+
+   -- | Check if we already compiled this version of cabal into a private
+   -- package-db
+   cachedCabalPkg :: FilePath -> MaybeT IO (Either ExitCode FilePath)
+   cachedCabalPkg chdir = do
+       db_exists <- liftIO $ cabalPkgDbExists opts cabalVer
+       case db_exists of
+         False -> mzero
+         True -> liftIO $ do
+             db <- cabalPkgDb opts cabalVer
+             compileWithPkg chdir (Just db)
+
+   -- | See if we're in a cabal source tree
+   compileCabalSource :: FilePath -> MaybeT IO (Either ExitCode FilePath)
+   compileCabalSource chdir = do
+       let couldBeSrcDir = takeDirectory distdir
+           cabalFile = couldBeSrcDir </> "Cabal.cabal"
+       cabal <- liftIO $ doesFileExist cabalFile
+       case cabal of
+         False -> mzero
+         True -> liftIO $ do
+           ver <- cabalFileVersion <$> readFile cabalFile
+           compileWithCabalTree chdir ver couldBeSrcDir
+
+   -- | Compile the requested cabal version into an isolated package-db
+   compileSandbox :: FilePath -> IO (Either ExitCode FilePath)
+   compileSandbox chdir = do
+       db <- installCabal opts cabalVer `E.catch`
+             \(SomeException _) -> errorInstallCabal cabalVer
+       compileWithPkg chdir (Just db)
+
+   compileWithCabalTree chdir ver srcDir =
+       compile opts $ Compile chdir (Just srcDir) Nothing ver []
+
+   compileWithPkg chdir mdb =
+       compile opts $ Compile chdir Nothing mdb cabalVer [cabalPkgId cabalVer]
+
+   cabalPkgId v = "Cabal-" ++ showVersion v
+
+-- errorNoCabal :: Version -> a
+-- errorNoCabal cabalVer = panic $ printf "\
+-- \No appropriate Cabal package found, wanted version %s.\n"
+--  where
+--    sver = showVersion cabalVer
+
+errorInstallCabal :: Version -> a
+errorInstallCabal cabalVer = panic $ printf "\
+\Installing Cabal version %s failed.\n\
+\n\
+\You have two choices now:\n\
+\- Either you install this version of Cabal in your globa/luser package-db\n\
+\  somehow\n\
+\n\
+\- Or you can see if you can update your cabal-install to use a different\n\
+\  version of the Cabal library that we can build with:\n\
+\    $ cabal install cabal-install --constraint 'Cabal > %s'\n\
+\n\
+\To check the version cabal-install is currently using try:\n\
+\    $ cabal --version\n" sver sver
+ where
+   sver = showVersion cabalVer
+
+data Compile = Compile {
+      cabalHelperSourceDir :: FilePath,
+      cabalSourceDir :: Maybe FilePath,
+      packageDb      :: Maybe FilePath,
+      cabalVersion   :: Version,
+      packageDeps    :: [String]
+    }
+
+compile :: Options -> Compile -> IO (Either ExitCode FilePath)
+compile Options {..} Compile {..} = do
+    outdir <- appDataDir
+    createDirectoryIfMissing True outdir
+    exe <- exePath cabalVersion
+
+    let Version (mj:mi:_) _ = cabalVersion
+    let ghc_opts =
+             concat [
+          [ "-outputdir", outdir
+          , "-o", exe
+          , "-optP-DCABAL_HELPER=1"
+          , "-optP-DCABAL_MAJOR=" ++ show mj
+          , "-optP-DCABAL_MINOR=" ++ show mi
+          ],
+          maybeToList $ ("-package-db="++) <$> packageDb,
+          map ("-i"++) $ cabalHelperSourceDir:maybeToList cabalSourceDir,
+          concatMap (\p -> ["-package", p]) packageDeps,
+          [ "--make",  cabalHelperSourceDir </> "CabalHelper/Main.hs" ]
+         ]
+
+    -- TODO: touch exe after, ghc doesn't do that if the input files didn't
+    -- actually change
+    rv <- callProcessStderr' Nothing ghcProgram ghc_opts
+    return $ case rv of
+               ExitSuccess -> Right exe
+               e@(ExitFailure _) -> Left e
+
+exePath :: Version -> IO FilePath
+exePath cabalVersion = do
+    outdir <- appDataDir
+    return $ outdir </> "cabal-helper-" ++ showVersion version -- our ver
+                     ++ "-Cabal-" ++ showVersion cabalVersion
+
+cachedExe :: Version -> IO (Maybe FilePath)
+cachedExe cabalVersion = do
+   exe <- exePath cabalVersion
+   exists <- doesFileExist exe
+   return $ if exists then Just exe else Nothing
+
+callProcessStderr' :: Maybe FilePath -> FilePath -> [String] -> IO ExitCode
+callProcessStderr' mwd exe args = do
+  (_, _, _, h) <- createProcess (proc exe args) { std_out = UseHandle stderr
+                                                , cwd = mwd }
+  waitForProcess h
+
+callProcessStderr :: Maybe FilePath -> FilePath -> [String] -> IO ()
+callProcessStderr mwd exe args = do
+  rv <- callProcessStderr' mwd exe args
+  case rv of
+    ExitSuccess -> return ()
+    ExitFailure v -> processFailedException "callProcessStderr" exe args v
+
+processFailedException :: String -> String -> [String] -> Int -> IO a
+processFailedException fn exe args rv =
+      panic $ concat [fn, ": ", exe, " "
+                     , intercalate " " (map show args)
+                     , " (exit " ++ show rv ++ ")"]
+
+installCabal :: Options -> Version -> IO FilePath
+installCabal opts ver = do
+  appdir <- appDataDir
+  hPutStr stderr $ printf "\
+\cabal-helper-wrapper: Installing a private copy of Cabal, this might take a\n\
+\while but will only happen once per Cabal version.\n\
+\\n\
+\If anything goes horribly wrong just delete this directory and try again:\n\
+\    %s\n\
+\\n\
+\If you want to avoid this automatic installation altogether install version\n\
+\%s of Cabal manually (into your user or global package-db):\n\
+\    $ cabal install Cabal-%s\n\
+\..." appdir (showVersion ver) (showVersion ver)
+
+  db <- createPkgDb opts ver
+  callProcessStderr (Just "/") (cabalProgram opts) $ concat
+      [
+        [ "--package-db=clear"
+        , "--package-db=global"
+        , "--package-db=" ++ db
+        , "--prefix=" ++ db </> "prefix"
+        , "-v0"
+        , "--with-ghc=" ++ ghcProgram opts
+        ]
+        , if ghcPkgProgram opts /= ghcPkgProgram defaultOptions
+            then [ "--with-ghc-pkg=" ++ ghcPkgProgram opts ]
+            else []
+        , [ "install", "Cabal-"++showVersion ver ]
+      ]
+  hPutStrLn stderr "Done"
+  return db
+
+ghcVersion :: Options -> IO Version
+ghcVersion Options {..} = do
+    parseVer . trim <$> readProcess ghcProgram ["--numeric-version"] ""
+
+ghcPkgVersion :: Options -> IO Version
+ghcPkgVersion Options {..} = do
+    parseVer . trim <$> readProcess ghcPkgProgram ["--numeric-version"] ""
+
+trim :: String -> String
+trim = dropWhileEnd isSpace
+
+createPkgDb :: Options -> Version -> IO FilePath
+createPkgDb opts@Options {..} ver = do
+  db <- cabalPkgDb opts ver
+  exists <- doesDirectoryExist db
+  when (not exists) $ callProcessStderr Nothing ghcPkgProgram ["init", db]
+  return db
+
+cabalPkgDb :: Options -> Version -> IO FilePath
+cabalPkgDb opts ver = do
+  appdir <- appDataDir
+  ghcVer <- ghcVersion opts
+  return $ appdir </> "Cabal-" ++ showVersion ver ++ "-db-" ++ showVersion ghcVer
+
+cabalPkgDbExists :: Options -> Version -> IO Bool
+cabalPkgDbExists opts ver = do
+  db <- cabalPkgDb opts ver
+  dexists <- doesDirectoryExist db
+  case dexists of
+    False -> return False
+    True -> do
+      vers <- listCabalVersions' opts (Just db)
+      return $ ver `elem` vers
+
+listCabalVersions :: Options -> IO [Version]
+listCabalVersions opts = listCabalVersions' opts Nothing
+
+-- TODO: Include sandbox? Probably only relevant for build-type:custom projects.
+listCabalVersions' :: Options -> Maybe FilePath -> IO [Version]
+listCabalVersions' Options {..} mdb = do
+  let mdbopt = ("--package-db="++) <$> mdb
+      opts = ["list", "--simple-output", "Cabal"] ++ maybeToList mdbopt
+
+  catMaybes . map (fmap snd . parsePkgId . fromString) . words
+          <$> readProcess ghcPkgProgram opts ""
+
+-- | Find @version: XXX@ delcaration in a cabal file
+cabalFileVersion :: String -> Version
+cabalFileVersion cabalFile = do
+  fromJust $ parseVer . extract <$> find ("version" `isPrefixOf`) ls
+ where
+  ls = map (map toLower) $ lines cabalFile
+  extract = dropWhile (/=':') >>> dropWhile isSpace >>> takeWhile (not . isSpace)
diff --git a/Distribution/Helper.hs b/Distribution/Helper.hs
new file mode 100644
index 0000000..84a23aa
--- /dev/null
+++ b/Distribution/Helper.hs
@@ -0,0 +1,278 @@
+-- ghc-mod: Making Haskell development *more* fun
+-- Copyright (C) 2015  Daniel Gröber <dxld ÄT darkboxed DOT org>
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+{-# LANGUAGE CPP, FlexibleContexts, ConstraintKinds, DeriveDataTypeable #-}
+module Distribution.Helper (
+    Programs(..)
+
+  -- * Running Queries
+  , Query
+  , runQuery
+  , runKQuery
+  , runKQuery_
+
+  -- * Queries against Cabal\'s on disk state
+
+  , entrypoints
+  , sourceDirs
+  , ghcOptions
+  , ghcSrcOptions
+  , ghcPkgOptions
+
+  -- * Managing @dist/@
+  , reconfigure
+  , writeAutogenFiles
+
+  -- * $libexec related error handling
+  , LibexecNotFoundError(..)
+  , libexecNotFoundError
+  ) where
+
+import Control.Applicative
+import Control.Arrow
+import Control.Monad
+import Control.Monad.IO.Class
+import Control.Monad.State.Strict
+import Control.Monad.Reader
+import Control.Exception
+import Data.Monoid
+import Data.List
+import Data.Default
+import Data.Typeable
+import System.Environment
+import System.FilePath
+import System.Directory
+import System.Process
+import Text.Printf
+
+import Paths_cabal_helper (getLibexecDir)
+import CabalHelper.Types
+
+-- | Paths or names of various programs we need.
+data Programs = Programs {
+      cabalProgram  :: FilePath,
+      ghcProgram    :: FilePath,
+      ghcPkgProgram :: FilePath
+    }
+
+instance Default Programs where
+    def = Programs "cabal" "ghc" "ghc-pkg"
+
+data SomeLocalBuildInfo = SomeLocalBuildInfo {
+      slbiEntrypoints   :: [(ChComponentName, ChEntrypoint)],
+      slbiSourceDirs    :: [(ChComponentName, [String])],
+      slbiGhcOptions    :: [(ChComponentName, [String])],
+      slbiGhcSrcOptions :: [(ChComponentName, [String])],
+      slbiGhcPkgOptions :: [(ChComponentName, [String])]
+    } deriving (Eq, Ord, Read, Show)
+
+-- | Caches helper executable result so it doesn't have to be run more than once
+-- as reading in Cabal's @LocalBuildInfo@ datatype from disk is very slow but
+-- running all possible queries against it at once is cheap.
+newtype Query m a = Query { unQuery :: StateT (Maybe SomeLocalBuildInfo)
+                                         (ReaderT (Programs, FilePath) m) a }
+
+type MonadQuery m = ( MonadIO m
+                    , MonadState (Maybe SomeLocalBuildInfo) m
+                    , MonadReader (Programs, FilePath) m)
+
+run r s action = flip runReaderT r (flip evalStateT s (unQuery action))
+
+-- | @runQuery query distdir@. Run a 'Query'. @distdir@ is where Cabal's
+-- @setup-config@ file is located.
+runQuery :: Monad m
+         => Query m a
+         -> FilePath -- ^ Path to @dist/@
+         -> m a
+runQuery action fp = run (def, fp) Nothing action
+
+-- | Run a 'Query' as an Arrow by wrapping it in a 'Kleisli' constructor.
+runKQuery :: Monad m
+          => Kleisli (Query m) a b
+          -> FilePath -- ^ Path to @dist/@
+          -> a
+          -> m b
+runKQuery (Kleisli action) fp a = run (def, fp) Nothing (action a)
+
+-- | Same as 'runKQuery' but pass unit as input to the arrow.
+runKQuery_ :: Monad m
+           => Kleisli (Query m) () b
+           -> FilePath -- ^ Path to @dist/@
+           -> m b
+runKQuery_ (Kleisli action) fp = run (def, fp) Nothing (action ())
+
+getSlbi :: MonadQuery m => m SomeLocalBuildInfo
+getSlbi = do
+  s <- get
+  case s of
+    Nothing -> do
+            slbi <- getSomeConfigState
+            put (Just slbi)
+            return slbi
+    Just slbi -> return slbi
+
+-- | Modules or files Cabal would have the compiler build directly. Can be used
+-- to compute the home module closure for a component.
+entrypoints   :: MonadIO m => Query m [(ChComponentName, ChEntrypoint)]
+
+-- | A component's @source-dirs@ field, beware as if this is empty implicit
+-- behaviour in GHC kicks in.
+sourceDirs    :: MonadIO m => Query m [(ChComponentName, [FilePath])]
+
+-- | All options cabal would pass to GHC.
+ghcOptions    :: MonadIO m => Query m [(ChComponentName, [String])]
+
+-- | Only search path related GHC options.
+ghcSrcOptions :: MonadIO m => Query m [(ChComponentName, [String])]
+
+-- | Only package related GHC options, sufficient for things don't need to
+-- access any home modules.
+ghcPkgOptions :: MonadIO m => Query m [(ChComponentName, [String])]
+
+entrypoints   = Query $ slbiEntrypoints   `liftM` getSlbi
+sourceDirs    = Query $ slbiSourceDirs    `liftM` getSlbi
+ghcOptions    = Query $ slbiGhcOptions    `liftM` getSlbi
+ghcSrcOptions = Query $ slbiGhcSrcOptions `liftM` getSlbi
+ghcPkgOptions = Query $ slbiGhcPkgOptions `liftM` getSlbi
+
+-- | Run @cabal configure@
+reconfigure :: MonadIO m
+            => Programs -- ^ Program paths
+            -> [String] -- ^ Command line arguments to be passed to @cabal@
+            -> m ()
+reconfigure progs cabalOpts = do
+    let progOpts =
+            [ "--with-ghc=" ++ ghcProgram progs ]
+            -- Only pass ghc-pkg if it was actually set otherwise we
+            -- might break cabal's guessing logic
+            ++ if ghcPkgProgram progs /= ghcPkgProgram def
+                 then [ "--with-ghc-pkg=" ++ ghcPkgProgram progs ]
+                 else []
+            ++ cabalOpts
+    _ <- liftIO $ readProcess (cabalProgram progs) ("configure":progOpts) ""
+    return ()
+
+getSomeConfigState :: MonadQuery m => m SomeLocalBuildInfo
+getSomeConfigState = ask >>= \(progs, distdir) -> do
+  let progArgs = [ "--with-ghc="     ++ ghcProgram progs
+                 , "--with-ghc-pkg=" ++ ghcPkgProgram progs
+                 , "--with-cabal="   ++ cabalProgram progs
+                 ]
+
+  let args = [ "entrypoints"
+             , "source-dirs"
+             , "ghc-options"
+             , "ghc-src-options"
+             , "ghc-pkg-options"
+             ] ++ progArgs
+
+  res <- liftIO $ do
+    exe  <- findLibexecExe "cabal-helper-wrapper"
+    out <- readProcess exe (distdir:args) ""
+    evaluate (read out) `catch` \(SomeException _) ->
+      error $ concat ["getSomeConfigState", ": ", exe, " "
+                     , intercalate " " (map show $ distdir:args)
+                     , " (read failed)"]
+
+  let [ Just (ResponseEntrypoints eps),
+        Just (ResponseStrings srcDirs),
+        Just (ResponseStrings ghcOpts),
+        Just (ResponseStrings ghcSrcOpts),
+        Just (ResponseStrings ghcPkgOpts) ] = res
+
+  return $ SomeLocalBuildInfo eps srcDirs ghcOpts ghcSrcOpts ghcPkgOpts
+
+-- | Create @cabal_macros.h@ and @Paths_\<pkg\>@ possibly other generated files
+-- in the usual place.
+writeAutogenFiles :: MonadIO m
+                  => FilePath -- ^ Path to the @dist/@ directory
+                  -> m ()
+writeAutogenFiles distdir = liftIO $ do
+  exe  <- findLibexecExe "cabal-helper-wrapper"
+  callProcess exe [distdir, "write-autogen-files"]
+
+-- | This exception is thrown by all 'runQuery' functions if the internal
+-- wrapper executable cannot be found. You may catch this and present the user
+-- an appropriate error message however the default is to print
+-- 'libexecNotFoundError'.
+data LibexecNotFoundError = LibexecNotFoundError String FilePath
+                          deriving (Typeable)
+instance Exception LibexecNotFoundError
+instance Show LibexecNotFoundError where
+  show (LibexecNotFoundError exe dir) =
+    libexecNotFoundError exe dir "https://github.com/DanielG/cabal-helper/issues"
+
+findLibexecExe :: String -> IO FilePath
+findLibexecExe "cabal-helper-wrapper" = do
+    libexecdir <- getLibexecDir
+    let exeName = "cabal-helper-wrapper"
+        exe = libexecdir </> exeName
+
+    exists <- doesFileExist exe
+
+    if exists
+       then return exe
+       else do
+         mdir <- tryFindCabalHelperTreeLibexecDir
+         case mdir of
+           Nothing ->
+               error $ throw $ LibexecNotFoundError exeName libexecdir
+           Just dir ->
+               return $ dir </> "dist" </> "build" </> exeName </> exeName
+findLibexecExe exe = error $ "findLibexecExe: Unknown executable: " ++ exe
+
+tryFindCabalHelperTreeLibexecDir :: IO (Maybe FilePath)
+tryFindCabalHelperTreeLibexecDir = do
+  exe <- getExecutablePath'
+  dir <- case takeFileName exe of
+    "ghc" -> do -- we're probably in ghci; try CWD
+        getCurrentDirectory
+    _ ->
+        return $ (!!4) $ iterate takeDirectory exe
+  exists <- doesFileExist $ dir </> "cabal-helper.cabal"
+  return $ if exists
+             then Just dir
+             else Nothing
+
+libexecNotFoundError :: String   -- ^ Name of the executable we were trying to
+                                 -- find
+                     -> FilePath -- ^ Path to @$libexecdir@
+                     -> String   -- ^ URL the user will be directed towards to
+                                 -- report a bug.
+                     -> String
+libexecNotFoundError exe dir reportBug = printf
+ ( "Could not find $libexecdir/%s\n"
+ ++"\n"
+ ++"If you are a developer set the environment variable\n"
+ ++"`cabal_helper_libexecdir' to override $libexecdir[1]. The following will\n"
+ ++"work in the cabal-helper source tree:\n"
+ ++"\n"
+ ++"    $ export cabal_helper_libexecdir=$PWD/dist/build/%s\n"
+ ++"\n"
+ ++"[1]: %s\n"
+ ++"\n"
+ ++"If you don't know what I'm talking about something went wrong with your\n"
+ ++"installation. Please report this problem here:\n"
+ ++"\n"
+ ++"    %s") exe exe dir reportBug
+
+getExecutablePath' :: IO FilePath
+getExecutablePath' =
+#if MIN_VERSION_base(4,6,0)
+    getExecutablePath
+#else
+    getProgName
+#endif
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..dba13ed
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,661 @@
+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU Affero General Public License is a free, copyleft license for
+software and other kinds of works, specifically designed to ensure
+cooperation with the community in the case of network server software.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+our General Public Licenses are intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+  Developers that use our General Public Licenses protect your rights
+with two steps: (1) assert copyright on the software, and (2) offer
+you this License which gives you legal permission to copy, distribute
+and/or modify the software.
+
+  A secondary benefit of defending all users' freedom is that
+improvements made in alternate versions of the program, if they
+receive widespread use, become available for other developers to
+incorporate.  Many developers of free software are heartened and
+encouraged by the resulting cooperation.  However, in the case of
+software used on network servers, this result may fail to come about.
+The GNU General Public License permits making a modified version and
+letting the public access it on a server without ever releasing its
+source code to the public.
+
+  The GNU Affero General Public License is designed specifically to
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+to the community.  It requires the operator of a network server to
+provide the source code of the modified version running there to the
+users of that server.  Therefore, public use of a modified version, on
+a publicly accessible server, gives the public access to the source
+code of the modified version.
+
+  An older license, called the Affero General Public License and
+published by Affero, was designed to accomplish similar goals.  This is
+a different license, not a version of the Affero GPL, but Affero has
+released a new version of the Affero GPL which permits relicensing under
+this license.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
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+
+  13. Remote Network Interaction; Use with the GNU General Public License.
+
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+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero 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 Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<http://www.gnu.org/licenses/>.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
index 0000000..05a0ae1
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,70 @@
+#!/usr/bin/env runhaskell
+{-# LANGUAGE RecordWildCards #-}
+import Distribution.Simple
+import Distribution.Simple.Setup
+import Distribution.Simple.Install
+import Distribution.Simple.InstallDirs as ID
+import Distribution.Simple.LocalBuildInfo
+import Distribution.PackageDescription
+
+import Control.Applicative
+import Data.List
+import Data.Maybe
+import System.FilePath
+
+main :: IO ()
+main = defaultMainWithHooks $ simpleUserHooks { copyHook = xInstallTargetHook }
+
+xInstallTargetHook ::
+    PackageDescription -> LocalBuildInfo -> UserHooks -> CopyFlags -> IO ()
+xInstallTargetHook pd lbi _uh cf = do
+  let (extended, regular) = partition (isJust . installTarget) (executables pd)
+
+  let pd_regular = pd { executables = regular }
+
+  _ <- flip mapM extended $ \exe -> do
+    putStrLn $ "extended "  ++ show (exeName exe)
+
+    let
+        idirtpl          = installDirTemplates lbi
+        env              = installDirsTemplateEnv idirtpl
+        libexecdir'      = fromPathTemplate (libexecdir idirtpl)
+
+        pd_extended      = onlyExePackageDesc [exe] pd
+        install_target   = fromJust $ installTarget exe
+        install_target'  = ID.substPathTemplate env install_target
+        -- $libexec isn't a real thing :/ so we have to simulate it
+        install_target'' = substLibExec' libexecdir' install_target'
+
+    let lbi' = lbi {
+                 installDirTemplates =
+                     (installDirTemplates lbi) {
+                   bindir = install_target''
+                 }
+               }
+
+    install pd_extended lbi' cf
+
+  install pd_regular lbi cf
+
+ where
+   installTarget :: Executable -> Maybe PathTemplate
+   installTarget exe =
+    toPathTemplate <$> lookup "x-install-target" (customFieldsBI $ buildInfo exe)
+
+   substLibExec libexecdir "$libexecdir" = libexecdir
+   substLibExec _ comp = comp
+
+   substLibExec' dir =
+       withPT $
+           withSP $ map (substLibExec dir . dropTrailingPathSeparator)
+
+
+   withPT f pt = toPathTemplate $ f (fromPathTemplate pt)
+   withSP f p  = joinPath $ f (splitPath p)
+
+onlyExePackageDesc :: [Executable] -> PackageDescription -> PackageDescription
+onlyExePackageDesc exes pd = emptyPackageDescription {
+                     package = package pd
+                   , executables = exes
+                   }
diff --git a/cabal-helper.cabal b/cabal-helper.cabal
new file mode 100644
index 0000000..5b74af5
--- /dev/null
+++ b/cabal-helper.cabal
@@ -0,0 +1,67 @@
+name:                cabal-helper
+version:             0.1.0.0
+synopsis:            Simple interface to Cabal's configuration state used by ghc-mod
+description:
+    CabalHelper provides a library which wraps the internal use of executables
+    to lift the restrictions imposed by linking against versions of GHC before
+    @7.10@.
+
+    CabalHelper uses a wrapper executable to compile the actual cabal-helper
+    executable at runtime while linking against an arbitrary version of
+    Cabal. This runtime-compiled helper executable is then used to extract
+    various bits and peices from Cabal on disk state (dist/setup-config) written
+    by it's configure command.
+
+    In addition to this the wrapper executable also supports installing any
+    version of Cabal from hackage in case it cannot be found in any available
+    package database. The wrapper installs these instances of the Cabal library
+    into a private package database so as to not interfere with the user's
+    packages.
+
+    Furthermore the wrapper supports one special case namely reading a state
+    file for Cabal itself. This is needed as Cabal compiles it's Setup.hs using
+    itself and not using any version of Cabal installed in any package database.
+
+    Currently CabalHelper supports @Cabal >= 1.16@.
+
+license:             AGPL-3
+license-file:        LICENSE
+author:              Daniel Gröber <dxld@darkboxed.org>
+maintainer:          dxld@darkboxed.org
+category:            Distribution
+build-type:          Simple
+cabal-version:       >=1.10
+
+source-repository head
+  type:     git
+  location: https://github.com/DanielG/cabal-helper.git
+
+library
+  exposed-modules:     Distribution.Helper
+  build-depends:       base >= 4.5 && < 5
+  default-language:    Haskell2010
+  Build-Depends:       base
+                     , data-default
+                     , directory
+                     , filepath
+                     , transformers
+                     , mtl
+                     , process
+
+
+Executable cabal-helper-wrapper
+  Default-Language:    Haskell2010
+  Other-Extensions:    TemplateHaskell
+  Main-Is:             CabalHelper/Wrapper.hs
+  Other-Modules:       Paths_cabal_helper
+  GHC-Options:         -Wall
+  X-Install-Target:    $libexecdir
+  Build-Depends:       base >= 4.5 && < 5
+                     , bytestring
+                     , Cabal
+                     , directory
+                     , filepath
+                     , process
+                     , transformers
+                     , template-haskell
+                     , temporary