Make dot and ls dependencies work without ghc installed

ChangeLog.md

@@ -97,6 +97,7 @@ Bug fixes:
   [#4314](https://github.com/commercialhaskell/stack/pull/4314)
 * Add `--cabal-files` flag to `stack ide targets` command.
 * Don't download ghc when using `stack clean`.
+* `dot` and `ls dependencies` commands no longer require GHC to be installed. Also, ensures the `--no-install-ghc` flag is respected. See: [#4390](https://github.com/commercialhaskell/stack/issues/4390)
 
 ## v1.9.1
 

src/Stack/Runners.hs

@@ -3,6 +3,7 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE RankNTypes #-}
 
 -- | Utilities for running stack commands.
 module Stack.Runners
@@ -261,10 +262,18 @@ munlockFile Nothing = return ()
 munlockFile (Just lk) = liftIO $ unlockFile lk
 
 -- Plumbing for --test and --bench flags
+-- Force enable --no-install-ghc and --skip-ghc-check flags
 withBuildConfigDot :: DotOpts -> GlobalOpts -> RIO EnvConfig () -> IO ()
-withBuildConfigDot opts go f = withBuildConfig go' f
+withBuildConfigDot opts go = withBuildConfig (updateGlobalOpts go)
   where
-    go' =
-        (if dotTestTargets opts then set (globalOptsBuildOptsMonoidL.buildOptsMonoidTestsL) (Just True) else id) $
-        (if dotBenchTargets opts then set (globalOptsBuildOptsMonoidL.buildOptsMonoidBenchmarksL) (Just True) else id)
-        go
+    updateGlobalOpts
+      = updateOpts (dotTestTargets opts)  (globalOptsBuildOptsMonoidL.buildOptsMonoidTestsL)      (Just True)
+      . updateOpts (dotBenchTargets opts) (globalOptsBuildOptsMonoidL.buildOptsMonoidBenchmarksL) (Just True)
+      . set (globalOptsL.configMonoidSkipGHCCheckL) (Just True)
+      . set (globalOptsL.configMonoidInstallGHCL)   (Just False)
+
+-- helper function for update some option
+updateOpts :: Bool -> Lens' opts v -> v -> opts -> opts
+updateOpts isRequired opt v
+  | isRequired = set opt v
+  | otherwise  = id

src/Stack/Setup.hs

@@ -206,6 +206,17 @@ instance Show SetupException where
     show UnsupportedSetupConfiguration =
         "I don't know how to install GHC on your system configuration, please install manually"
 
+checkDownloadCompiler :: (HasConfig env, HasGHCVariant env)
+  => SetupOpts
+  -> WithDownloadCompiler
+  -> RIO env (Maybe ExtraDirs, Maybe CompilerBuild, Bool)
+checkDownloadCompiler _     SkipDownloadCompiler = return (Nothing, Nothing, False)
+checkDownloadCompiler sopts WithDownloadCompiler
+  | installIfMissing = ensureCompiler sopts
+  | otherwise = return (Nothing, Nothing, False)
+  where
+    installIfMissing = soptsInstallIfMissing sopts
+
 -- | Modify the environment variables (like PATH) appropriately, possibly doing installation too
 setupEnv :: (HasBuildConfig env, HasGHCVariant env)
          => Maybe Text -- ^ Message to give user when necessary GHC is not available
@@ -234,10 +245,7 @@ setupEnv mResolveMissingGHC = do
             , soptsGHCJSBootOpts = ["--clean"]
             }
 
-    (mghcBin, mCompilerBuild, _) <-
-      case bcDownloadCompiler bconfig of
-        SkipDownloadCompiler -> return (Nothing, Nothing, False)
-        WithDownloadCompiler -> ensureCompiler sopts
+    (mghcBin, mCompilerBuild, _) <- checkDownloadCompiler sopts (bcDownloadCompiler bconfig)
 
     -- Modify the initial environment to include the GHC path, if a local GHC
     -- is being used

src/Stack/Types/Config.hs

@@ -163,6 +163,8 @@ module Stack.Types.Config
   ,loadedSnapshotL
   ,shouldForceGhcColorFlag
   ,appropriateGhcColorFlag
+  ,configMonoidSkipGHCCheckL
+  ,configMonoidInstallGHCL
   -- * Lens reexport
   ,view
   ,to
@@ -1984,3 +1986,13 @@ appropriateGhcColorFlag :: (HasRunner env, HasEnvConfig env)
 appropriateGhcColorFlag = f <$> shouldForceGhcColorFlag
   where f True = Just ghcColorForceFlag
         f False = Nothing
+
+configMonoidSkipGHCCheckL :: Lens' ConfigMonoid (Maybe Bool)
+configMonoidSkipGHCCheckL = 
+  lens (getFirst . configMonoidSkipGHCCheck)
+       (\configMonoid t -> configMonoid {configMonoidSkipGHCCheck = First t})
+
+configMonoidInstallGHCL :: Lens' ConfigMonoid (Maybe Bool)
+configMonoidInstallGHCL = 
+  lens (getFirst . configMonoidInstallGHC)
+       (\configMonoid t -> configMonoid {configMonoidInstallGHC = First t})