Add code action for remove all redundant imports

[berberman]

This PR implements haskell/haskell-language-server#339. The code removing single redundant import can be reused.

[pepeiborra]

Does it work? Can you add a test please?

[berberman]

Any instruction of tests? I'm not sure what to add in removeImportTests.

[pepeiborra]

All the tests live in test/exe/Main.hs
You can find the tests for the redundant imports code action there too

[berberman]

removeImportTests :: TestTree
removeImportTests = testGroup "remove import actions"
  [ testSession "redundant" $ do
      let contentA = T.unlines
            [ "module ModuleA where"
            ]
      _docA <- createDoc "ModuleA.hs" "haskell" contentA
      let contentB = T.unlines
            [ "{-# OPTIONS_GHC -Wunused-imports #-}"
            , "module ModuleB where"
            , "import ModuleA"
            , "stuffB :: Integer"
            , "stuffB = 123"
            ]
      docB <- createDoc "ModuleB.hs" "haskell" contentB
      _ <- waitForDiagnostics
      -- two code actions are expected
      -- one for remove the single redundant import in range, the other for remove all
      [CACodeAction action@CodeAction { _title = actionTitle }] 
          <- getCodeActions docB (Range (Position 2 0) (Position 2 5))
      liftIO $ "Remove import" @=? actionTitle
      executeCodeAction action
      -- the import has been removed so far...
      contentAfterAction <- documentContents docB
      let expectedContentAfterAction = T.unlines
            [ "{-# OPTIONS_GHC -Wunused-imports #-}"
            , "module ModuleB where"
            , "stuffB :: Integer"
            , "stuffB = 123"
            ]
      liftIO $ expectedContentAfterAction @=? contentAfterAction
  , -- ......

executeCodeAction here applies the edit which removes the single redundant import to the document, so I have no where to place the test of remove all redundant imports. Can I extract TextEdit from CodeAction then use applyEdit to avoid modifying the document in session directly, or I have to create separate tests?

[pepeiborra]

Please create a separate test

[berberman]

Ok. For removeImportTests, we have to modify each pattern matching on getCodeActions, because there will be a new code action. I think [CACodeAction action@CodeAction { _title = actionTitle }, _] would be enough, since we know that "Remove all redundant imports" always appears later than "Remove import".

[pepeiborra]

Looks good with some minor suggestions. Thank you for adding a test!

[berberman]

Thanks for the review and suggestions! I enum more cases in the test.

[pepeiborra]

Merged! Thanks again, this is an awesome contribution I've been wanting for a long time.