Look for stack.yaml before selecting .cabal location as project root (haskell#1531)

Author: fendor

hie-plugin-api/Haskell/Ide/Engine/Cradle.hs

@@ -201,7 +201,10 @@ Just (Ex (ProjLocV2File { plProjectDirV2 = "/Foo/"}))
 
 In the given example, it is not guaranteed which project type is found,
 it is only guaranteed that it will not identify the project
-as a cabal v1-project.
+as a cabal v1-project. Note that with cabal-helper version (1.0),
+by default a *.cabal file is identified as a 'ProjLocV2Dir' project.
+The same issue as before exists and we look for a 'ProjLocV2File' or
+'ProjLocStackYaml' before deciding that 'ProjLocV2Dir' marks the project root.
 
 Note that this will not return any project types for which the corresponding
 build tool is not on the PATH. This is "stack" and "cabal" for stack and cabal
@@ -219,13 +222,13 @@ findCabalHelperEntryPoint fp = do
   let supportedProjs = filter (\x -> supported x isStackInstalled isCabalInstalled) allProjs
   debugm $ "These projects have the build tools installed: " ++ show (map (\(Ex x) -> show x) supportedProjs)
 
-  case filter (\p -> isCabalNewProject p || isStackProject p) supportedProjs of
+  case filter (\p -> isCabalV2FileProject p || isStackProject p) supportedProjs of
     (x:_) -> return $ Just x
-    []    -> case filter isCabalOldProject supportedProjs of
+    []    -> case filter isCabalProject supportedProjs of
       (x:_) -> return $ Just x
       []    -> return Nothing
     where
-      supported :: (Ex ProjLoc) -> Bool -> Bool -> Bool
+      supported :: Ex ProjLoc -> Bool -> Bool -> Bool
       supported (Ex ProjLocStackYaml {}) stackInstalled _ = stackInstalled
       supported (Ex ProjLocV2Dir {}) _ cabalInstalled = cabalInstalled
       supported (Ex ProjLocV2File {}) _ cabalInstalled = cabalInstalled
@@ -235,13 +238,14 @@ findCabalHelperEntryPoint fp = do
       isStackProject (Ex ProjLocStackYaml {}) = True
       isStackProject _ = False
 
-      isCabalNewProject (Ex ProjLocV2Dir {}) = True
-      isCabalNewProject (Ex ProjLocV2File {}) = True
-      isCabalNewProject _ = False
+      isCabalV2FileProject (Ex ProjLocV2File {}) = True
+      isCabalV2FileProject _ = False
 
-      isCabalOldProject (Ex ProjLocV1Dir {}) = True
-      isCabalOldProject (Ex ProjLocV1CabalFile {}) = True
-      isCabalOldProject _ = False
+      isCabalProject (Ex ProjLocV1CabalFile {}) = True
+      isCabalProject (Ex ProjLocV1Dir {}) = True
+      isCabalProject (Ex ProjLocV2File {}) = True
+      isCabalProject (Ex ProjLocV2Dir {}) = True
+      isCabalProject _ = False
 
 {- | Given a FilePath, find the cradle the FilePath belongs to.