1 files changed, 48 insertions, 0 deletions
diff --git a/pkgs/development/compilers/ghcs/nix_ghc_pkg_tool.hs b/pkgs/development/compilers/ghcs/nix_ghc_pkg_tool.hs
new file mode 100644
index 00000000000..494b37807fa
--- /dev/null
+++ b/pkgs/development/compilers/ghcs/nix_ghc_pkg_tool.hs
@@ -0,0 +1,48 @@
+-- packages: filepath,Cabal,directory
+{-# OPTIONS_GHC -fglasgow-exts #-}
+module Main where
+import Distribution.InstalledPackageInfo (InstalledPackageInfo (..))
+import Distribution.Package (showPackageId)
+import System.FilePath
+import System.Environment
+import System.Directory
+import System.IO
+import System.Exit
+import Data.List
+
+usage = unlines [
+    " usage a) <app-name> split in_path out_path"
+  , "       b) <app-anme> join out_path"
+  , "This small helper executable servers two purposes:"
+  , "a) split the main package db created by ghc installation into single libs"
+  , "   so that nix can add them piecwise as needed to buildInputs"
+  , "b) merge databases into one single file, so when building a library"
+  , "   we can create one db containing all dependencies passed by GHC_PACKAGE_PATH"
+  , "   I think this is a better solution than patching and mantaining cabal so"
+  , "   that it support GHC_PACKAGE_PATH (not only by accident) ?"
+  ]
+
+mySplit :: (Eq Char) => [Char] ->[[ Char ]]
+mySplit [] = []
+mySplit list = let (l, l') = span (not . (`elem` ":;")) list
+                    in l: mySplit (drop 1 l')
+
+myReadFile f = doesFileExist f >>= \fe ->
+    if fe then readFile f
+          else do hPutStrLn stderr $ "unable to read file " ++ f
+                  exitWith (ExitFailure 1)
+
+main = do
+  args <- getArgs
+  case args of
+    ["split", inFile, outDir] -> do
+      -- prior to 6.9.x (when exactly) this must be InstalledPackageInfo only (not InstalledPackageInfo_ String) 
+      -- (packagedb :: [InstalledPackageInfo_ String] ) <- fmap read $ myReadFile inFile
+      (packagedb :: [InstalledPackageInfo] ) <- fmap read $ myReadFile inFile
+      mapM_ (\pi -> let fn = outDir </> (showPackageId $ package pi) ++ ".conf"
+                    in writeFile fn (show [pi])
+            ) packagedb
+    ["join", outpath] -> do
+      getEnv "GHC_PACKAGE_PATH" >>= mapM myReadFile . nub . mySplit 
+        >>= writeFile outpath . show . concat . map (read :: String -> [InstalledPackageInfo])
+    _ -> putStrLn usage