From f53faf87340f900efa5b4d0649e313a16b0f2e76 Mon Sep 17 00:00:00 2001
From: Jacek Generowicz <jacg@my-post-office.net>
Date: Fri, 13 Sep 2019 01:08:57 +0200
Subject: [PATCH] Add code action for GHC's suggestions for not-found module

---
 src/Development/IDE/LSP/CodeAction.hs | 10 ++++++++++
 test/exe/Main.hs                      | 22 ++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/Development/IDE/LSP/CodeAction.hs b/src/Development/IDE/LSP/CodeAction.hs
index 3430deb9..e9d58f20 100644
--- a/src/Development/IDE/LSP/CodeAction.hs
+++ b/src/Development/IDE/LSP/CodeAction.hs
@@ -20,6 +20,7 @@ import Language.Haskell.LSP.Messages
 import qualified Data.Rope.UTF16 as Rope
 import Data.Char
 import Data.Maybe
+import Data.List
 import qualified Data.Text as T
 
 -- | Generate code actions.
@@ -97,6 +98,15 @@ suggestAction contents Diagnostic{_range=_range@Range{..},..}
     | exts@(_:_) <- filter (`Set.member` ghcExtensions) $ T.split (not . isAlpha) $ T.replace "-X" "" _message
         = [("Add " <> x <> " extension", [TextEdit (Range (Position 0 0) (Position 0 0)) $ "{-# LANGUAGE " <> x <> " #-}\n"]) | x <- exts]
 
+-- src/Development/IDE/Core/Compile.hs:58:1: error:
+--     Could not find module ‘Data.Cha’
+--     Perhaps you meant Data.Char (from base-4.12.0.0)
+    | "Could not find module" `T.isInfixOf` _message
+    , "Perhaps you meant"     `T.isInfixOf` _message
+      = map proposeModule $ nub $ findSuggestedModules _message where
+      findSuggestedModules = (map (head . T.words) . drop 2 . T.lines)
+      proposeModule mod = ("replace with " <> mod, [TextEdit _range mod])
+
 suggestAction _ _ = []
 
 mkRenameEdit :: Maybe T.Text -> Range -> T.Text -> TextEdit
diff --git a/test/exe/Main.hs b/test/exe/Main.hs
index 2376dad3..041ee5b2 100644
--- a/test/exe/Main.hs
+++ b/test/exe/Main.hs
@@ -213,6 +213,7 @@ codeActionTests = testGroup "code actions"
   [ renameActionTests
   , typeWildCardActionTests
   , removeImportTests
+  , importRenameActionTests
   ]
 
 renameActionTests :: TestTree
@@ -413,6 +414,27 @@ removeImportTests = testGroup "remove import actions"
       liftIO $ expectedContentAfterAction @=? contentAfterAction
   ]
 
+importRenameActionTests :: TestTree
+importRenameActionTests = testGroup "import rename actions"
+  [ testSession "Data.Mape -> Data.Map"   $ check "Map"
+  , testSession "Data.Mape -> Data.Maybe" $ check "Maybe" ] where
+  check modname = do
+      let content = T.unlines
+            [ "module Testing where"
+            , "import Data.Mape"
+            ]
+      doc <- openDoc' "Testing.hs" "haskell" content
+      _ <- waitForDiagnostics
+      actionsOrCommands <- getCodeActions doc (Range (Position 2 8) (Position 2 16))
+      let [changeToMap] = [action | CACodeAction action@CodeAction{ _title = actionTitle } <- actionsOrCommands, ("Data." <> modname) `T.isInfixOf` actionTitle ]
+      executeCodeAction changeToMap
+      contentAfterAction <- documentContents doc
+      let expectedContentAfterAction = T.unlines
+            [ "module Testing where"
+            , "import Data." <> modname
+            ]
+      liftIO $ expectedContentAfterAction @=? contentAfterAction
+
 ----------------------------------------------------------------------
 -- Utils