Merge pull request #4885 from qrilka/nix-mode-without-project

Allow nix mode commands to run outside of a project

ChangeLog.md

@@ -17,6 +17,10 @@ Bug fixes:
 * Fix to allow dependencies on specific versions of local git repositories. See
   [#4862](https://github.com/commercialhaskell/stack/pull/4862)
 
+* Allow Stack commands to be run in Nix mode without having a project file
+  available. See
+  [#4854](https://github.com/commercialhaskell/stack/issues/4864).
+
 
 ## v2.1.1.1
 

src/Stack/Nix.hs

@@ -24,7 +24,6 @@ import           Stack.Constants (platformVariantEnvVar,inNixShellEnvVar,inConta
 import           Stack.Types.Config
 import           Stack.Types.Docker
 import           Stack.Types.Nix
-import           Stack.Docker (getProjectRoot)
 import           System.Environment (getArgs,getExecutablePath,lookupEnv)
 import qualified System.FilePath  as F
 import           RIO.Process (processContextL, exec)
@@ -43,10 +42,11 @@ runShellAndExit = do
    local (set processContextL envOverride) $ do
      let cmnd = escape exePath
          args' = map escape args
-     projectRoot <- getProjectRoot
-     mshellFile <-
-         traverse (resolveFile projectRoot) $
-         nixInitFile (configNix config)
+
+     mshellFile <- case configProjectRoot config of
+         Just projectRoot ->
+             traverse (resolveFile projectRoot) $ nixInitFile (configNix config)
+         Nothing -> pure Nothing
 
      -- This will never result in double loading the build config, since:
      --