Fail when trying to override an existing file

lib/Commands.hs

@@ -7,6 +7,7 @@ module Commands
     FixFilePathsOptions (..),
     fixFilePaths,
     fixFilePaths',
+    Error (..),
     errorToText,
   )
 where
@@ -27,13 +28,16 @@ import Sound.HTagLib qualified as HTagLib
 import Sound.HTagLib.Extra qualified as HTagLib
 import UnliftIO.Exception qualified as Exception
 
-newtype Error = UnableToFormatFile (Path.Path Path.Abs Path.File)
-  deriving (Show)
+data Error
+  = UnableToFormatFile (Path.Path Path.Abs Path.File)
+  | TargetFileAlreadyExists (Path.Path Path.Abs Path.File)
+  deriving (Show, Eq)
 
 instance Exception.Exception Error
 
 errorToText :: Error -> Text
 errorToText (UnableToFormatFile file) = "Unable to format file: " <> show file
+errorToText (TargetFileAlreadyExists file) = "Target file already exists: " <> show file
 
 getTags :: (MonadIO m) => Path.Path Path.Abs Path.File -> m ()
 getTags = putTextLn . AudioTrack.asText <=< AudioTrack.getTags
@@ -132,6 +136,10 @@ fixFilePaths' FixFilePathsOptions {..} fromFile = do
   if toFileAbs == fromFile
     then pure Nothing
     else do
+      whenM (Path.doesFileExist toFileAbs) $
+        Exception.throwIO $
+          TargetFileAlreadyExists toFileAbs
+
       unless fiDryRun $ do
         Path.ensureDir $ Path.parent toFileAbs
 

tests/Tests/Commands.hs

@@ -17,6 +17,7 @@ import Test.Hspec.Expectations (shouldBe)
 import Test.Tasty qualified as Tasty
 import Test.Tasty.HUnit qualified as Tasty
 import Tests.Common qualified as Common
+import UnliftIO.Exception qualified as Exception
 
 test :: Tasty.TestTree
 test = Tasty.testGroup "Commands" [testFixFilePaths]
@@ -98,6 +99,10 @@ testFixFilePaths =
 
           exists <- Path.doesFileExist cover
           exists `shouldBe` True,
+      Tasty.testCase "fails when target already exists" $
+        testTargetAlreadyExists False,
+      Tasty.testCase "fails when target already exists (dry run)" $
+        testTargetAlreadyExists True,
       Tasty.testCase "rename and move the cover image" $
         Common.withTenTracksFilesInSubdir [reldir|./input|] $ \dir _ -> do
           let inputDir = dir </> [reldir|input|]
@@ -124,6 +129,20 @@ testFixFilePaths =
           newCoverExists `shouldBe` True
     ]
 
+testTargetAlreadyExists :: Bool -> Tasty.Assertion
+testTargetAlreadyExists dryRun =
+  Common.withOneTrackFile $ \dir file -> do
+    targetFile <-
+      Unsafe.fromJust
+        <$> Commands.fixFilePaths' (fixFilePathsOptions True False dir) file
+    Path.ensureDir $ Path.parent targetFile
+    -- Create a dummy file where the file should be moved
+    System.writeFile (Path.toFilePath targetFile) ""
+    result <-
+      Exception.try $
+        Commands.fixFilePaths' (fixFilePathsOptions dryRun False dir) file
+    result `shouldBe` Left (Commands.TargetFileAlreadyExists targetFile)
+
 check :: (MonadIO m) => Path.Path Path.Abs Path.File -> m (Either Track.Error ())
 check filename = do
   track <- AudioTrack.getTags filename

tests/Tests/Common.hs

@@ -5,6 +5,7 @@ module Tests.Common
     tenTracksAlbum',
     withTenTracksFiles,
     withTenTracksFilesInSubdir,
+    withOneTrackFile,
   )
 where
 
@@ -46,6 +47,28 @@ withTenTracksFiles ::
 withTenTracksFiles withTempDirAndAlbum =
   withTenTracksFilesInSubdir [reldir|./|] withTempDirAndAlbum
 
+withOneTrackFile ::
+  (Path.Path Path.Abs Path.Dir -> Path.Path Path.Abs Path.File -> IO ()) ->
+  Tasty.Assertion
+withOneTrackFile action =
+  Path.withSystemTempDir "htagcli" $ \dir -> do
+    let file = dir </> [relfile|1-sample.mp3|]
+        track =
+          AudioTrack.AudioTrack
+            { AudioTrack.atFile = file,
+              AudioTrack.atTitle = HTagLib.mkTitle "Track 1",
+              AudioTrack.atArtist = HTagLib.mkArtist "Artist",
+              AudioTrack.atAlbumArtist = HTagLib.mkAlbumArtist "Album Artist",
+              AudioTrack.atAlbum = HTagLib.mkAlbum "Album",
+              AudioTrack.atGenre = HTagLib.mkGenre "Pop",
+              AudioTrack.atYear = HTagLib.mkYear 2025,
+              AudioTrack.atTrack = HTagLib.mkTrackNumber 1,
+              AudioTrack.atDisc = Nothing
+            }
+    Path.copyFile [relfile|./data/sample.mp3|] file
+    AudioTrack.setTags track
+    action dir file
+
 tenTracksAlbum :: Album.Album
 tenTracksAlbum =
   tenTracksAlbum'