cabal-doctest: Add support for --with-compiler

src/Cabal.hs

@@ -22,7 +22,7 @@ externalCommand args = do
 run :: String -> [String] -> IO ()
 run cabal args = do
 
-  Paths{..} <- paths cabal
+  Paths{..} <- paths cabal args
 
   let
     doctest = cache </> "doctest" <> "-" <> Info.version
@@ -53,9 +53,10 @@ run cabal args = do
     : "--build-depends=QuickCheck"
     : "--build-depends=template-haskell"
     : ("--repl-options=-ghci-script=" <> script)
-    : "--with-compiler" : doctest
-    : "--with-hc-pkg" : ghcPkg
-    : args) >>= waitForProcess >>= exitWith
+    : args ++ [
+      "--with-compiler", doctest
+    , "--with-hc-pkg", ghcPkg
+    ]) >>= waitForProcess >>= exitWith
 
 writeFileAtomically :: FilePath -> String -> IO ()
 writeFileAtomically name contents = do

src/Cabal/Paths.hs

@@ -24,8 +24,8 @@ data Paths = Paths {
 , cache :: FilePath
 } deriving (Eq, Show)
 
-paths :: FilePath -> IO Paths
-paths cabal = do
+paths :: FilePath -> [String] -> IO Paths
+paths cabal args = do
   cabalVersion <- strip <$> readProcess cabal ["--numeric-version"] ""
 
   let
@@ -35,7 +35,7 @@ paths cabal = do
   when (parseVersion cabalVersion < Just required) $ do
     die $ "'cabal-install' version " <> showVersion required <> " or later is required, but 'cabal --numeric-version' returned " <> cabalVersion <> "."
 
-  values <- parseFields <$> readProcess cabal ["path", "-v0"] ""
+  values <- parseFields <$> readProcess cabal ("path" : args ++ ["-v0"]) ""
 
   let
     getPath :: String -> String -> IO FilePath

test/Cabal/PathsSpec.hs

@@ -6,16 +6,17 @@ import           Test.Hspec
 
 import           System.Directory
 
+import           Cabal ()
 import           Cabal.Paths
 
 spec :: Spec
 spec = do
   describe "paths" $ do
     it "returns the path to 'ghc'" $ do
-      (paths "cabal" >>= doesFileExist . ghc) `shouldReturn` True
+      (paths "cabal" [] >>= doesFileExist . ghc) `shouldReturn` True
 
     it "returns the path to 'ghc-pkg'" $ do
-      (paths "cabal" >>= doesFileExist . ghcPkg) `shouldReturn` True
+      (paths "cabal" [] >>= doesFileExist . ghcPkg) `shouldReturn` True
 
     it "returns the path to Cabal's cache directory" $ do
-      (paths "cabal" >>= doesDirectoryExist . cache) `shouldReturn` True
+      (paths "cabal" [] >>= doesDirectoryExist . cache) `shouldReturn` True