Place cabal constraints in config file, not args #723

It seems that, on Windows, the large number of arguments causes the process
package to give the incredibly misleading error message:

C:\Users\chris\AppData\Roaming\local\bin\cabal.exe: streamingProcess: does not exist (No such file or directory)

This workaround isn't just a hack, but a good thing: putting constraints in the
config file is an improvement in general, so I'm happy to keep it. Nonetheless,
this is something that should be fixed at the process package level.

src/Stack/Init.hs

@@ -155,7 +155,7 @@ getDefaultResolver cabalfps gpds initOpts =
                     return (ResolverSnapshot snap, flags, Map.empty)
                 Nothing -> return (resolver, Map.empty, Map.empty)
         MethodSolver -> do
-            (ghcVersion, extraDeps) <- cabalSolver (map parent cabalfps) []
+            (ghcVersion, extraDeps) <- cabalSolver (map parent cabalfps) Map.empty []
             return
                 ( ResolverGhc ghcVersion
                 , Map.filter (not . Map.null) $ fmap snd extraDeps

src/Stack/Solver.hs

@@ -34,14 +34,16 @@ import           System.Directory            (copyFile,
                                               getTemporaryDirectory)
 import qualified System.FilePath             as FP
 import           System.IO.Temp
+import           System.Process (rawSystem)
 import           System.Process.Read
 
 cabalSolver :: (MonadIO m, MonadLogger m, MonadMask m, MonadBaseControl IO m, MonadReader env m, HasConfig env)
             => [Path Abs Dir] -- ^ cabal files
-            -> [String] -- ^ additional arguments, usually constraints
+            -> Map PackageName Version -- ^ constraints
+            -> [String] -- ^ additional arguments
             -> m (MajorVersion, Map PackageName (Version, Map FlagName Bool))
-cabalSolver cabalfps cabalArgs = withSystemTempDirectory "cabal-solver" $ \dir -> do
-    configLines <- getCabalConfig dir
+cabalSolver cabalfps constraints cabalArgs = withSystemTempDirectory "cabal-solver" $ \dir -> do
+    configLines <- getCabalConfig dir constraints
     let configFile = dir FP.</> "cabal.config"
     liftIO $ S.writeFile configFile $ encodeUtf8 $ T.unlines configLines
 
@@ -115,12 +117,13 @@ getGhcMajorVersion menv = do
 
 getCabalConfig :: (MonadReader env m, HasConfig env, MonadIO m, MonadThrow m)
                => FilePath -- ^ temp dir
+               -> Map PackageName Version -- ^ constraints
                -> m [Text]
-getCabalConfig dir = do
+getCabalConfig dir constraints = do
     indices <- asks $ configPackageIndices . getConfig
     remotes <- mapM goIndex indices
     let cache = T.pack $ "remote-repo-cache: " ++ dir
-    return $ cache : remotes
+    return $ cache : remotes ++ map goConstraint (Map.toList constraints)
   where
     goIndex index = do
         src <- configPackageIndex $ indexName index
@@ -135,6 +138,13 @@ getCabalConfig dir = do
             , ":http://0.0.0.0/fake-url"
             ]
 
+    goConstraint (name, version) = T.concat
+        [ "constraint: "
+        , T.pack $ packageNameString name
+        , "=="
+        , T.pack $ versionString version
+        ]
+
 -- | Determine missing extra-deps
 solveExtraDeps :: (MonadReader env m, HasEnvConfig env, MonadIO m, MonadMask m, MonadLogger m, MonadBaseControl IO m, HasHttpManager env)
                => Bool -- ^ modify stack.yaml?
@@ -155,18 +165,11 @@ solveExtraDeps modStackYaml = do
     let packages = Map.union
             (bcExtraDeps bconfig)
             (fmap mpiVersion snapshot)
-        constraints = map
-            (\(k, v) -> concat
-                [ "--constraint="
-                , packageNameString k
-                , "=="
-                , versionString v
-                ])
-            (Map.toList packages)
 
     (_ghc, extraDeps) <- cabalSolver
         (Map.keys $ envConfigPackages econfig)
-        constraints
+        packages
+        []
 
     let newDeps = extraDeps `Map.difference` packages
         newFlags = Map.filter (not . Map.null) $ fmap snd newDeps