Merge pull request #6273 from commercialhaskell/fix6269

Fix #6269 Implement notify-if-nix-on-path

ChangeLog.md

@@ -14,6 +14,10 @@ Behavior changes:
   the Stack root, and deletes any corresponding to a `setup-<hash>.hs` or
   `setup-shim-<hash>.hs` file, to avoid GHC issue
   [#21250](https://gitlab.haskell.org/ghc/ghc/-/issues/21250).
+* If Stack's Nix integration is not enabled, Stack will notify the user if a
+  `nix` executable is on the PATH. This usually indicates the Nix package
+  manager is available. In YAML configuration files, the `notify-if-nix-on-path`
+  key is introduced, to allow the notification to be muted if unwanted.
 
 Other enhancements:
 

doc/nix_integration.md

@@ -82,6 +82,12 @@ nix:
 The equivalent command line flag (which will prevail) is `--[no-]nix`. Passing
 any `--nix-*` option on the command line will imply the `--nix` option.
 
+If Nix integration is not enabled, Stack will notify the user if a `nix`
+executable is on the PATH. If that notification is unwanted, it can be muted by
+setting Stack's configuration option
+[`notify-if-nix-on-path`](yaml_configuration.md#notify-if-nix-on-path) to
+`false`.
+
 With Nix integration enabled, `stack build` and `stack exec` will automatically
 launch themselves in a local build environment (using `nix-shell` behind the
 scenes). It is not necessary to run `stack setup`, unless you want to cache a

doc/yaml_configuration.md

@@ -1131,6 +1131,15 @@ for details).
 For further information, see the
 [Nix integration](nix_integration.md#configuration) documentation.
 
+### notify-if-nix-on-path
+
+:octicons-tag-24: UNRELEASED
+
+Default: `true`
+
+If Stack's integration with the Nix package manager is not enabled, should Stack
+notify the user if a `nix` executable is on the PATH?
+
 ### package-index
 
 [:octicons-tag-24: 2.9.3](https://github.com/commercialhaskell/stack/releases/tag/v2.9.3)

src/Stack/Config.hs

@@ -423,6 +423,7 @@ configFromConfigMonoid
           fromFirst "https://hackage.haskell.org/" configMonoidHackageBaseUrl
         configHideSourcePaths = fromFirstTrue configMonoidHideSourcePaths
         configRecommendUpgrade = fromFirstTrue configMonoidRecommendUpgrade
+        configNotifyIfNixOnPath = fromFirstTrue configMonoidNotifyIfNixOnPath
         configNoRunCompile = fromFirstFalse configMonoidNoRunCompile
     configAllowDifferentUser <-
       case getFirst configMonoidAllowDifferentUser of

src/Stack/Constants.hs

@@ -12,6 +12,7 @@ module Stack.Constants
   , haskellDefaultPreprocessorExts
   , stackProgName
   , stackProgName'
+  , nixProgName
   , stackDotYaml
   , stackWorkEnvVar
   , stackRootEnvVar
@@ -173,6 +174,10 @@ instance Exception ConstantsException where
 stackProgName' :: Text
 stackProgName' = T.pack stackProgName
 
+-- | Name of the Nix package manager command
+nixProgName :: String
+nixProgName = "nix"
+
 -- | Extensions used for Haskell modules. Excludes preprocessor ones.
 haskellFileExts :: [Text]
 haskellFileExts = ["hs", "hsc", "lhs"]

src/Stack/Runners.hs

@@ -18,15 +18,21 @@ module Stack.Runners
   , ShouldReexec (..)
   ) where
 
-import           RIO.Process ( mkDefaultProcessContext )
+import qualified Data.ByteString.Lazy.Char8 as L8
+import           RIO.Process
+                   ( findExecutable, mkDefaultProcessContext, proc
+                   , readProcess
+                   )
 import           RIO.Time ( addUTCTime, getCurrentTime )
 import           Stack.Build.Target ( NeedTargets (..) )
 import           Stack.Config
                    ( getInContainer, getInNixShell, loadConfig, withBuildConfig
                    , withNewLogFunc
                    )
 import           Stack.Constants
-                   ( defaultTerminalWidth, maxTerminalWidth, minTerminalWidth )
+                   ( defaultTerminalWidth, maxTerminalWidth, minTerminalWidth
+                   , nixProgName
+                   )
 import           Stack.DefaultColorWhen ( defaultColorWhen )
 import qualified Stack.Docker as Docker
 import qualified Stack.Nix as Nix
@@ -140,6 +146,49 @@ withConfig shouldReexec inner =
 reexec :: RIO Config a -> RIO Config a
 reexec inner = do
   nixEnable' <- asks $ nixEnable . configNix
+  notifyIfNixOnPath <- asks configNotifyIfNixOnPath
+  when (not nixEnable' && notifyIfNixOnPath) $ do
+    eNix <- findExecutable nixProgName
+    case eNix of
+      Left _ -> pure ()
+      Right nix -> proc nix ["--version"] $ \pc -> do
+        let nixProgName' = style Shell (fromString nixProgName)
+            muteMsg = fillSep
+              [ flow "To mute this message in future, set"
+              , style Shell (flow "notify-if-nix-on-path: false")
+              , flow "in Stack's configuration."
+              ]
+            reportErr errMsg = prettyWarn $
+                 fillSep
+                   [ nixProgName'
+                   , flow "is on the PATH"
+                   , parens (fillSep ["at", style File (fromString nix)])
+                   , flow "but Stack encountered the following error with"
+                   , nixProgName'
+                   , style Shell "--version" <> ":"
+                   ]
+              <> blankLine
+              <> errMsg
+              <> blankLine
+              <> muteMsg
+              <> line
+        res <- tryAny (readProcess pc)
+        case res of
+          Left e -> reportErr (ppException e)
+          Right (ec, out, err) -> case ec of
+            ExitFailure _ -> reportErr $ string (L8.unpack err)
+            ExitSuccess -> do
+              let trimFinalNewline str = case reverse str of
+                    '\n' : rest -> reverse rest
+                    _ -> str
+              prettyWarn $ fillSep
+                   [ fromString (trimFinalNewline $ L8.unpack out)
+                   , flow "is on the PATH"
+                   , parens (fillSep ["at", style File (fromString nix)])
+                   , flow "but Stack's Nix integration is disabled."
+                   , muteMsg
+                   ]
+                <> line
   dockerEnable' <- asks $ dockerEnable . configDocker
   case (nixEnable', dockerEnable') of
     (True, True) -> throwIO DockerAndNixInvalid

src/Stack/Types/Config.hs

@@ -179,6 +179,9 @@ data Config = Config
     -- ^ Enable GHC hiding source paths?
   , configRecommendUpgrade    :: !Bool
     -- ^ Recommend a Stack upgrade?
+  , configNotifyIfNixOnPath   :: !Bool
+    -- ^ Notify if the Nix package manager (nix) is on the PATH, but
+    -- Stack's Nix integration is not enabled?
   , configNoRunCompile   :: !Bool
     -- ^ Use --no-run and --compile options when using `stack script`
   , configStackDeveloperMode  :: !Bool

src/Stack/Types/ConfigMonoid.hs

@@ -168,6 +168,8 @@ data ConfigMonoid = ConfigMonoid
     -- ^ See 'configHideSourcePaths'
   , configMonoidRecommendUpgrade   :: !FirstTrue
     -- ^ See 'configRecommendUpgrade'
+  , configMonoidNotifyIfNixOnPath  :: !FirstTrue
+    -- ^ See 'configNotifyIfNixOnPath'
   , configMonoidCasaOpts :: !CasaOptsMonoid
     -- ^ Casa configuration options.
   , configMonoidCasaRepoPrefix     :: !(First CasaRepoPrefix)
@@ -338,6 +340,8 @@ parseConfigMonoidObject rootDir obj = do
     FirstTrue <$> obj ..:? configMonoidHideSourcePathsName
   configMonoidRecommendUpgrade <-
     FirstTrue <$> obj ..:? configMonoidRecommendUpgradeName
+  configMonoidNotifyIfNixOnPath <-
+    FirstTrue <$> obj ..:? configMonoidNotifyIfNixOnPathName
   configMonoidCasaOpts <-
     jsonSubWarnings (obj ..:? configMonoidCasaOptsName ..!= mempty)
   configMonoidCasaRepoPrefix <-
@@ -515,6 +519,9 @@ configMonoidHideSourcePathsName = "hide-source-paths"
 configMonoidRecommendUpgradeName :: Text
 configMonoidRecommendUpgradeName = "recommend-stack-upgrade"
 
+configMonoidNotifyIfNixOnPathName :: Text
+configMonoidNotifyIfNixOnPathName = "notify-if-nix-on-path"
+
 configMonoidCasaOptsName :: Text
 configMonoidCasaOptsName = "casa"