Monitor imported cabal.project files as well

Fixes #10255

Author: hasufell

cabal-install-solver/src/Distribution/Solver/Types/ProjectConfigPath.hs

@@ -6,6 +6,7 @@ module Distribution.Solver.Types.ProjectConfigPath
     -- * Project Config Path Manipulation
       ProjectConfigPath(..)
     , projectConfigPathRoot
+    , projectConfigPathAll
     , nullProjectConfigPath
     , consProjectConfigPath
     , unconsProjectConfigPath
@@ -217,6 +218,10 @@ docProjectConfigPathFailReason vr pcp
 projectConfigPathRoot :: ProjectConfigPath -> FilePath
 projectConfigPathRoot (ProjectConfigPath xs) = last xs
 
+-- | Get all paths.
+projectConfigPathAll :: ProjectConfigPath -> [FilePath]
+projectConfigPathAll (ProjectConfigPath xs) = NE.toList xs
+
 -- | Used by some tests as a dummy "unused" project root.
 nullProjectConfigPath :: ProjectConfigPath
 nullProjectConfigPath = ProjectConfigPath $ "unused" :| []

cabal-install/src/Distribution/Client/ProjectConfig.hs

@@ -853,14 +853,21 @@ readProjectFileSkeletonGen
       exists <- liftIO $ doesFileExist extensionFile
       if exists
         then do
-          monitorFiles [monitorFileHashed extensionFile]
           pcs <- liftIO $ parseConfig extensionFile
-          monitorFiles $ map monitorFileHashed (projectConfigPathRoot <$> projectSkeletonImports pcs)
+
+          -- we need to monitor the main project file as well as all (possibly recursive) imports
+          let allProjectFiles = map makeAbsolute . nub . concat $ projectConfigPathAll <$> projectSkeletonImports pcs
+          monitorFiles $ map monitorFileHashed allProjectFiles
+
           return pcs
         else do
           monitorFiles [monitorNonExistentFile extensionFile]
           return mempty
     where
+      -- do we prefer absolute paths for cache monitoring?
+      makeAbsolute f
+        | isAbsolute f = f
+        | otherwise = distProjectRootDirectory dir </> f
       extensionFile = (distProjectFile dir) extensionName
 
 -- There are 3 different variants of the project parsing function.