cabal-read: init

krebs/5pkgs/simple/cabal-read.nix

@@ -0,0 +1,35 @@
+{ writeHaskellPackage }:
+
+# Because `sed -n 's/.*\<ghc-options:\s\+\(.*\)/\1/p'` is too simple.
+writeHaskellPackage "cabal-read" {
+  executables.ghc-options = {
+    extra-depends = ["Cabal"];
+    text = /* haskell */ ''
+      module Main (main) where
+      import Data.List
+      import Data.Maybe
+      import Distribution.Compiler
+      import Distribution.PackageDescription.Parsec
+      import Distribution.Types.BuildInfo
+      import Distribution.Types.CondTree
+      import Distribution.Types.Executable
+      import Distribution.Types.GenericPackageDescription
+      import Distribution.Types.UnqualComponentName
+      import Distribution.Verbosity
+      import System.Environment
+      main :: IO ()
+      main = do
+          [path, name] <- getArgs
+
+          desc <- readGenericPackageDescription normal path
+
+          case lookup (mkUnqualComponentName name) (condExecutables desc) of
+            Just exe ->
+              putStrLn . intercalate " " . fromMaybe [] . lookup GHC
+                       . options . buildInfo . condTreeData $ exe
+
+            Nothing ->
+              error ("executable " <> name <> " not found in " <> path)
+    '';
+  };
+}