Nix: Select the correct GHC version in more cases.

Even when abstract resolver is provided.

Fixes #1641.

ChangeLog.md

@@ -23,6 +23,10 @@ Bug fixes:
   [Mailing list discussion](https://groups.google.com/d/msg/haskell-stack/iVGDG5OHYxs/FjUrR5JsDQAJ)
 - Gracefully handle invalid paths in error/warning messages
   [#1561](https://github.com/commercialhaskell/stack/issues/1561)
+- Nix: select the correct GHC version corresponding to the snapshot
+  even when an abstract resolver is passed via `--resolver` on the
+  command-line.
+  [#1641](https://github.com/commercialhaskell/stack/issues/1641)
 
 ## 1.0.0
 

src/Stack/Config.hs

@@ -234,7 +234,7 @@ configFromConfigMonoid configStackRoot configUserConfigPath mresolver mproject c
 
      configDocker <-
          dockerOptsFromMonoid (fmap fst mproject) configStackRoot mresolver configMonoidDockerOpts
-     configNix <- nixOptsFromMonoid (fmap fst mproject) mresolver configMonoidNixOpts os
+     configNix <- nixOptsFromMonoid configMonoidNixOpts os
 
      rawEnv <- liftIO getEnvironment
      pathsEnv <- augmentPathMap (map toFilePath configMonoidExtraPath)

src/Stack/Config/Nix.hs

@@ -19,32 +19,20 @@ import Control.Monad.Catch (throwM,MonadCatch)
 -- | Interprets NixOptsMonoid options.
 nixOptsFromMonoid
     :: (Monad m, MonadCatch m)
-    => Maybe Project
-    -> Maybe AbstractResolver
-    -> NixOptsMonoid
+    => NixOptsMonoid
     -> OS
     -> m NixOpts
-nixOptsFromMonoid mproject maresolver NixOptsMonoid{..} os = do
+nixOptsFromMonoid NixOptsMonoid{..} os = do
     let nixEnable = fromMaybe nixMonoidDefaultEnable nixMonoidEnable
         defaultPure = case os of
           OSX -> False
           _ -> True
         nixPureShell = fromMaybe defaultPure nixMonoidPureShell
-        mresolver = case maresolver of
-          Just (ARResolver resolver) -> Just resolver
-          Just _ -> Nothing
-          Nothing -> fmap projectResolver mproject
-        pkgs = fromMaybe [] nixMonoidPackages
-        nixPackages = case mproject of
-           Nothing -> pkgs
-           Just _ -> pkgs ++ [case mresolver of
-              Just (ResolverSnapshot (LTS x y)) ->
-                T.pack ("haskell.packages.lts-" ++ show x ++ "_" ++ show y ++ ".ghc")
-              _ -> T.pack "ghc"]
+        nixPackages = fromMaybe [] nixMonoidPackages
         nixInitFile = nixMonoidInitFile
         nixShellOptions = fromMaybe [] nixMonoidShellOptions
                           ++ prefixAll (T.pack "-I") (fromMaybe [] nixMonoidPath)
-    when (not (null pkgs) && isJust nixInitFile) $
+    when (not (null nixPackages) && isJust nixInitFile) $
        throwM NixCannotUseShellFileAndPackagesException
     return NixOpts{..}
   where prefixAll p (x:xs) = p : x : prefixAll p xs

src/Stack/Nix.hs

@@ -35,6 +35,7 @@ import           Path.IO
 import qualified Paths_stack as Meta
 import           Prelude -- Fix redundant import warnings
 import           Stack.Constants (stackProgName,platformVariantEnvVar)
+import           Stack.Config (makeConcreteResolver)
 import           Stack.Docker (reExecArgName)
 import           Stack.Exec (exec)
 import           System.Process.Read (getEnvOverride)
@@ -49,14 +50,15 @@ import           System.Exit (exitSuccess, exitWith)
 reexecWithOptionalShell
     :: M env m
     => Maybe (Path Abs Dir)
+    -> Maybe AbstractResolver
     -> IO ()
     -> m ()
-reexecWithOptionalShell mprojectRoot inner =
+reexecWithOptionalShell mprojectRoot maresolver inner =
   do config <- asks getConfig
      inShell <- getInShell
      isReExec <- asks getReExec
      if nixEnable (configNix config) && not inShell && not isReExec
-       then runShellAndExit mprojectRoot getCmdArgs
+       then runShellAndExit mprojectRoot maresolver getCmdArgs
        else liftIO inner
   where
     getCmdArgs = do
@@ -70,23 +72,30 @@ reexecWithOptionalShell mprojectRoot inner =
 runShellAndExit
     :: M env m
     => Maybe (Path Abs Dir)
+    -> Maybe AbstractResolver
     -> m (String, [String])
     -> m ()
-runShellAndExit mprojectRoot getCmdArgs = do
+runShellAndExit mprojectRoot maresolver getCmdArgs = do
      config <- asks getConfig
+     mresolver <- mapM makeConcreteResolver maresolver
      envOverride <- getEnvOverride (configPlatform config)
      (cmnd,args) <- fmap (escape *** map escape) getCmdArgs
      mshellFile <-
          traverse (resolveFile (fromMaybeProjectRoot mprojectRoot)) $
          nixInitFile (configNix config)
      let pkgsInConfig = nixPackages (configNix config)
+         pkgs =
+           pkgsInConfig ++ [case mresolver of
+             Just (ResolverSnapshot (LTS x y)) ->
+               T.pack ("haskell.packages.lts-" ++ show x ++ "_" ++ show y ++ ".ghc")
+             _ -> T.pack "ghc"]
          pureShell = nixPureShell (configNix config)
          nixopts = case mshellFile of
            Just fp -> [toFilePath fp]
            Nothing -> ["-E", T.unpack $ T.intercalate " " $ concat
                               [["with (import <nixpkgs> {});"
                                ,"runCommand \"myEnv\" {"
-                               ,"buildInputs=lib.optional stdenv.isLinux glibcLocales ++ ["],pkgsInConfig,["];"
+                               ,"buildInputs=lib.optional stdenv.isLinux glibcLocales ++ ["],pkgs,["];"
                                ,T.pack platformVariantEnvVar <> "=''nix'';"
                                ,T.pack inShellEnvVar <> "=1;"
                                ,"STACK_IN_NIX_EXTRA_ARGS=''"]

src/main/Main.hs

@@ -698,7 +698,7 @@ setupCmd SetupCmdOpts{..} go@GlobalOpts{..} = do
           (lcProjectRoot lc)
           Nothing
           (runStackTGlobal manager (lcConfig lc) go $
-           Nix.reexecWithOptionalShell (lcProjectRoot lc) $
+           Nix.reexecWithOptionalShell (lcProjectRoot lc) globalResolver $
            runStackLoggingTGlobal manager go $ do
               (wantedCompiler, compilerCheck, mstack) <-
                   case scoCompilerVersion of
@@ -864,7 +864,7 @@ withBuildConfigExt go@GlobalOpts{..} mbefore inner mafter = do
                  (lcProjectRoot lc)
                  mbefore
                  (runStackTGlobal manager (lcConfig lc) go $
-                    Nix.reexecWithOptionalShell (lcProjectRoot lc) (inner'' lk0))
+                    Nix.reexecWithOptionalShell (lcProjectRoot lc) globalResolver (inner'' lk0))
                  mafter
                  (Just $ liftIO $
                       do lk' <- readIORef curLk
@@ -1007,6 +1007,7 @@ execCmd ExecOpts {..} go@GlobalOpts{..} =
                         menv <- liftIO $ configEnvOverride config plainEnvSettings
                         Nix.reexecWithOptionalShell
                             (lcProjectRoot lc)
+                            globalResolver
                             (runStackTGlobal manager (lcConfig lc) go $
                                 exec menv cmd args))
                     Nothing