Fix failure with --isolate=dir --force

Fixes #695

lib/GHCup/Prelude/File/Posix.hs

@@ -48,6 +48,7 @@ import           Streamly.Internal.Data.Unfold.Type
 import qualified Streamly.Internal.Data.Unfold as U
 import           Streamly.Internal.Control.Concurrent ( withRunInIO )
 import           Streamly.Internal.Data.IOFinalizer   ( newIOFinalizer, runIOFinalizer )
+import GHC.IO.Exception (IOException(ioe_type), IOErrorType (..))
 
 
 -- | On unix, we can use symlinks, so we just get the
@@ -116,8 +117,18 @@ copyFile from to fail' = do
         let dflags = [ FD.oNofollow
                      , if fail' then FD.oExcl else FD.oTrunc
                      ]
+        let openFdHandle' = openFdHandle to SPI.WriteOnly dflags $ Just sourceFileMode
         bracket
-          (openFdHandle to SPI.WriteOnly dflags $ Just sourceFileMode)
+          (handleIO (\e -> if
+                              -- if we copy from regular file to symlink, we need
+                              -- to delete the symlink
+                              | ioe_type e == InvalidArgument
+                              , not fail' -> do
+                                 removeLink to
+                                 openFdHandle'
+                              | otherwise -> throwIO e
+                    )
+            openFdHandle')
           (hClose . snd)
           $ \(_, tH) -> do
               hSetBinaryMode fH True

lib/GHCup/Utils/Dirs.hs

@@ -465,22 +465,15 @@ withGHCupTmpDir :: ( MonadReader env m
                    , MonadMask m
                    , MonadIO m)
                 => m GHCupPath
-withGHCupTmpDir = do
-  Settings{keepDirs} <- getSettings
-  snd <$> withRunInIO (\run ->
-    run
-      $ allocate
-          (run mkGhcupTmpDir)
-          (\fp -> if -- we don't know whether there was a failure, so can only
-                     -- decide for 'Always'
-                     | keepDirs == Always -> pure ()
-                     | otherwise -> handleIO (\e -> run
-                        $ logDebug ("Resource cleanup failed for "
-                                   <> T.pack (fromGHCupPath fp)
-                                   <> ", error was: "
-                                   <> T.pack (displayException e)))
-                        . removePathForcibly
-                        $ fp))
+withGHCupTmpDir = snd <$> withRunInIO (\run ->
+  run
+    $ allocate
+        (run mkGhcupTmpDir)
+        (\fp ->
+            handleIO (\e -> run
+                $ logDebug ("Resource cleanup failed for " <> T.pack (fromGHCupPath fp) <> ", error was: " <> T.pack (displayException e)))
+            . removePathForcibly
+            $ fp))