From c27ea7fda3bcd8c7825ca8c44f360a9a88c295d0 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Mon, 8 Feb 2021 17:02:35 +0800
Subject: [PATCH 01/10] Add code action for hiding shadowed identifiers from
 imports

---
 .../src/Development/IDE/Plugin/CodeAction.hs  | 88 ++++++++++++++++++-
 1 file changed, 84 insertions(+), 4 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction.hs b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
index c5f0ae6067..72d2595c8d 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
@@ -58,6 +58,12 @@ import OccName
 import qualified GHC.LanguageExtensions as Lang
 import Control.Lens (alaf)
 import Data.Monoid (Ap(..))
+import TcRnTypes (TcGblEnv(..), ImportAvails(..))
+import HscTypes (ImportedModsVal(..), importedByUser)
+import RdrName (GlobalRdrElt(..), lookupGlobalRdrEnv)
+import SrcLoc (realSrcSpanStart)
+import Module (moduleEnvElts)
+import qualified Data.Map as M
 
 descriptor :: PluginId -> PluginDescriptor IdeState
 descriptor plId =
@@ -80,11 +86,13 @@ codeAction lsp state _ (TextDocumentIdentifier uri) _range CodeActionContext{_di
     let text = Rope.toText . (_text :: VirtualFile -> Rope.Rope) <$> contents
         mbFile = toNormalizedFilePath' <$> uriToFilePath uri
     diag <- fmap (\(_, _, d) -> d) . filter (\(p, _, _) -> mbFile == Just p) <$> getDiagnostics state
-    (ideOptions, join -> parsedModule, join -> env, join -> annotatedPS) <- runAction "CodeAction" state $
-      (,,,) <$> getIdeOptions
+    (ideOptions, join -> parsedModule, join -> env, join -> annotatedPS, join -> tcM, join -> har) <- runAction "CodeAction" state $
+      (,,,,,) <$> getIdeOptions
             <*> getParsedModule `traverse` mbFile
             <*> use GhcSession `traverse` mbFile
             <*> use GetAnnotatedParsedSource `traverse` mbFile
+            <*> use TypeCheck `traverse` mbFile
+            <*> use GetHieAst `traverse` mbFile
     -- This is quite expensive 0.6-0.7s on GHC
     let pkgExports = envPackageExports <$> env
     localExports <- readVar (exportsMap $ shakeExtras state)
@@ -93,7 +101,7 @@ codeAction lsp state _ (TextDocumentIdentifier uri) _range CodeActionContext{_di
       df = ms_hspp_opts . pm_mod_summary <$> parsedModule
       actions =
         [ mkCA title  [x] edit
-        | x <- xs, (title, tedit) <- suggestAction exportsMap ideOptions parsedModule text df annotatedPS x
+        | x <- xs, (title, tedit) <- suggestAction exportsMap ideOptions parsedModule text df annotatedPS tcM har x
         , let edit = WorkspaceEdit (Just $ Map.singleton uri $ List tedit) Nothing
         ]
       actions' = caRemoveRedundantImports parsedModule text diag xs uri
@@ -123,9 +131,11 @@ suggestAction
   -> Maybe T.Text
   -> Maybe DynFlags
   -> Maybe (Annotated ParsedSource)
+  -> Maybe TcModuleResult
+  -> Maybe HieAstResult
   -> Diagnostic
   -> [(T.Text, [TextEdit])]
-suggestAction packageExports ideOptions parsedModule text df annSource diag =
+suggestAction packageExports ideOptions parsedModule text df annSource tcM har diag =
     concat
    -- Order these suggestions by priority
     [ suggestSignature True diag
@@ -140,6 +150,7 @@ suggestAction packageExports ideOptions parsedModule text df annSource diag =
     , suggestAddTypeAnnotationToSatisfyContraints text diag
     , rewrite df annSource $ \df ps -> suggestConstraint df ps diag
     , rewrite df annSource $ \_ ps -> suggestImplicitParameter ps diag
+    , rewrite df annSource $ \_ ps -> suggestHideShadow ps tcM har diag
     ] ++ concat
     [  suggestNewDefinition ideOptions pm text diag
     ++ suggestNewImport packageExports pm diag
@@ -169,6 +180,75 @@ findInstanceHead df instanceHead decls =
 findDeclContainingLoc :: Position -> [Located a] -> Maybe (Located a)
 findDeclContainingLoc loc = find (\(L l _) -> loc `isInsideSrcSpan` l)
 
+-- This binding for ‘mod’ shadows the existing binding
+--   imported from ‘Prelude’ at haskell-language-server/ghcide/src/Development/IDE/Plugin/CodeAction.hs:10:8-40
+--   (and originally defined in ‘GHC.Real’)typecheck(-Wname-shadowing)
+suggestHideShadow :: ParsedSource -> Maybe TcModuleResult -> Maybe HieAstResult -> Diagnostic -> [(T.Text, [Rewrite])]
+suggestHideShadow pm@(L _ HsModule {hsmodImports}) mTcM mHar Diagnostic {_message, _range}
+  | Just tcM <- mTcM,
+    Just har <- mHar,
+    Just [identifier, modName, s] <-
+      matchRegexUnifySpaces
+        _message
+        "This binding for ‘([^`]+)’ shadows the existing binding imported from ‘([^`]+)’ at ([^ ]*)",
+    [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
+    isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
+    title <- "Hide " <> identifier <> " from " <> modName,
+    implicitPrelude <- null $ findImportDeclByModuleName hsmodImports "Prelude" =
+    if modName == "Prelude" && implicitPrelude
+      then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
+      else [(title, hideOrRemoveId hsmodImports (T.unpack identifier) (T.unpack modName))]
+  | otherwise = []
+
+hideOrRemoveId :: [LImportDecl GhcPs] -> String -> String -> [Rewrite]
+hideOrRemoveId lImportDecls identifier modName
+  | Just decl <- findImportDeclByModuleName lImportDecls modName =
+    [hideSymbol identifier decl]
+  | otherwise =
+    []
+
+findImportDeclByModuleName :: [LImportDecl GhcPs] -> String -> Maybe (LImportDecl GhcPs)
+findImportDeclByModuleName decls modName = flip find decls $ \case
+  (L _ ImportDecl {..}) -> modName == moduleNameString (unLoc ideclName)
+  _ -> error "impossible"
+
+isTheSameLine :: SrcSpan -> SrcSpan -> Bool
+isTheSameLine s1 s2
+  | Just sl1 <- getStartLine s1,
+    Just sl2 <- getStartLine s2 =
+    sl1 == sl2
+  | otherwise = False
+
+getStartLine :: SrcSpan -> Maybe Int
+getStartLine s
+  | RealSrcSpan s' <- s,
+    startLoc <- realSrcSpanStart s',
+    startLine <- srcLocLine startLoc =
+    Just startLine
+  | otherwise = Nothing
+
+isUnusedImportedId :: TcModuleResult -> HieAstResult -> String -> String -> SrcSpan -> Bool
+isUnusedImportedId
+  TcModuleResult {tmrTypechecked = TcGblEnv {tcg_imports = ImportAvails {imp_mods}}}
+  HAR {refMap = rf}
+  identifier
+  modName
+  importSpan
+    | occ <- mkVarOcc identifier,
+      impModsVals <- importedByUser . concat $ moduleEnvElts imp_mods,
+      Just rdrEnv <-
+        listToMaybe
+          [ imv_all_exports
+            | ImportedModsVal {..} <- impModsVals,
+              imv_name == mkModuleName modName,
+              isTheSameLine imv_span importSpan
+          ],
+      [GRE {..}] <- lookupGlobalRdrEnv rdrEnv occ,
+      importedIdentifier <- Right gre_name,
+      refs <- M.lookup importedIdentifier rf =
+      maybe True null refs
+    | otherwise = False
+
 suggestDisableWarning :: ParsedModule -> Maybe T.Text -> Diagnostic -> [(T.Text, [TextEdit])]
 suggestDisableWarning pm contents Diagnostic{..}
     | Just (StringValue (T.stripPrefix "-W" -> Just w)) <- _code =

From a8ea66415cc6503c993b2fde61a1369ac9a832d2 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Tue, 9 Feb 2021 13:28:45 +0800
Subject: [PATCH 02/10] Insert to the line above module decls if there are no
 existing import decls

---
 .../IDE/Plugin/CodeAction/ExactPrint.hs        | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
index 68198752c9..e7489ff75c 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
@@ -31,7 +31,7 @@ import Development.IDE.GHC.Compat hiding (parseExpr)
 import Development.IDE.GHC.ExactPrint
     ( Annotate, ASTElement(parseAST) )
 import FieldLabel (flLabel)
-import GhcPlugins (sigPrec)
+import GhcPlugins (sigPrec, mkRealSrcLoc)
 import Language.Haskell.GHC.ExactPrint
 import Language.Haskell.GHC.ExactPrint.Types (DeltaPos (DP), KeywordId (G), mkAnnKey)
 import Language.Haskell.LSP.Types
@@ -40,7 +40,6 @@ import Outputable (ppr, showSDocUnsafe, showSDoc)
 import Retrie.GHC (rdrNameOcc, unpackFS, mkRealSrcSpan, realSrcSpanEnd)
 import Development.IDE.Spans.Common
 import Development.IDE.GHC.Error
-import Safe (lastMay)
 import Data.Generics (listify)
 import GHC.Exts (IsList (fromList))
 
@@ -205,6 +204,7 @@ extendImport mparent identifier lDecl@(L l _) =
 -- extendImportTopLevel "foo" AST:
 --
 -- import A --> Error
+-- import A (foo) --> Error
 -- import A (bar) --> import A (bar, foo)
 extendImportTopLevel :: DynFlags -> String -> LImportDecl GhcPs -> TransformT (Either String) (LImportDecl GhcPs)
 extendImportTopLevel df idnetifier (L l it@ImportDecl {..})
@@ -408,13 +408,15 @@ deleteFromImport (T.pack -> symbol) (L l idecl) llies@(L lieLoc lies) _ =do
                   (filter ((/= symbol) . T.pack . unpackFS . flLabel . unLoc) flds)
         killLie v = Just v
 
+-- | Insert a import declaration hiding a symbole from Prelude
 hideImplicitPreludeSymbol
     :: String -> ParsedSource -> Maybe Rewrite
 hideImplicitPreludeSymbol symbol (L _ HsModule{..}) = do
-    existingImp <- lastMay hsmodImports
-    exisImpSpan <- realSpan $ getLoc existingImp
-    let indentation = srcSpanStartCol exisImpSpan
-        beg = realSrcSpanEnd exisImpSpan
+    let predLine old = mkRealSrcLoc (srcLocFile old) (srcLocLine old - 1) (srcLocCol old)
+        existingImpSpan =  (fmap (id,) . realSpan . getLoc) =<< lastMaybe hsmodImports
+        existingDeclSpan = (fmap (predLine, ) . realSpan . getLoc) =<< headMaybe hsmodDecls
+    (f, s) <- existingImpSpan <|> existingDeclSpan
+    let beg = f $ realSrcSpanEnd s
         ran = RealSrcSpan $ mkRealSrcSpan beg beg
     pure $ Rewrite ran $ \df -> do
         let symOcc = mkVarOcc symbol
@@ -424,6 +426,6 @@ hideImplicitPreludeSymbol symbol (L _ HsModule{..}) = do
         -- Re-labeling is needed to reflect annotations correctly
         L _ idecl0 <- liftParseAST @(ImportDecl GhcPs) df $ T.unpack impStmt
         let idecl = L ran idecl0
-        addSimpleAnnT idecl (DP (1,indentation - 1))
-            [(G AnnImport, DP (1, indentation - 1))]
+        addSimpleAnnT idecl (DP (1, 0))
+            [(G AnnImport, DP (1, 0))]
         pure idecl

From 368165b157f7be3a17e4beb528b23dac754fa686 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Tue, 9 Feb 2021 14:42:44 +0800
Subject: [PATCH 03/10] Support handling multi imports

---
 .../src/Development/IDE/Plugin/CodeAction.hs  | 51 ++++++++++++-------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction.hs b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
index 72d2595c8d..7d263b3326 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
@@ -64,6 +64,7 @@ import RdrName (GlobalRdrElt(..), lookupGlobalRdrEnv)
 import SrcLoc (realSrcSpanStart)
 import Module (moduleEnvElts)
 import qualified Data.Map as M
+import qualified Data.Set as S
 
 descriptor :: PluginId -> PluginDescriptor IdeState
 descriptor plId =
@@ -180,25 +181,44 @@ findInstanceHead df instanceHead decls =
 findDeclContainingLoc :: Position -> [Located a] -> Maybe (Located a)
 findDeclContainingLoc loc = find (\(L l _) -> loc `isInsideSrcSpan` l)
 
+-- Single:
 -- This binding for ‘mod’ shadows the existing binding
 --   imported from ‘Prelude’ at haskell-language-server/ghcide/src/Development/IDE/Plugin/CodeAction.hs:10:8-40
 --   (and originally defined in ‘GHC.Real’)typecheck(-Wname-shadowing)
+-- Multi:
+--This binding for ‘pack’ shadows the existing bindings
+--  imported from ‘Data.ByteString’ at B.hs:6:1-22
+--  imported from ‘Data.ByteString.Lazy’ at B.hs:8:1-27
+--  imported from ‘Data.Text’ at B.hs:7:1-16
+
 suggestHideShadow :: ParsedSource -> Maybe TcModuleResult -> Maybe HieAstResult -> Diagnostic -> [(T.Text, [Rewrite])]
 suggestHideShadow pm@(L _ HsModule {hsmodImports}) mTcM mHar Diagnostic {_message, _range}
-  | Just tcM <- mTcM,
-    Just har <- mHar,
-    Just [identifier, modName, s] <-
+  | Just [identifier, modName, s] <-
+      matchRegexUnifySpaces
+        _message
+        "This binding for ‘([^`]+)’ shadows the existing binding imported from ‘([^`]+)’ at ([^ ]*)"
+    = suggests identifier modName s
+  | Just [identifier] <-
       matchRegexUnifySpaces
         _message
-        "This binding for ‘([^`]+)’ shadows the existing binding imported from ‘([^`]+)’ at ([^ ]*)",
-    [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
-    isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
-    title <- "Hide " <> identifier <> " from " <> modName,
-    implicitPrelude <- null $ findImportDeclByModuleName hsmodImports "Prelude" =
-    if modName == "Prelude" && implicitPrelude
-      then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
-      else [(title, hideOrRemoveId hsmodImports (T.unpack identifier) (T.unpack modName))]
+        "This binding for ‘([^`]+)’ shadows the existing bindings",
+    Just matched <- allMatchRegexUnifySpaces _message "imported from ‘([^’]+)’ at ([^ ]*)",
+    mods <- [(modName, s) | [_, modName, s] <- matched],
+    result <- nubOrdBy (compare `on` fst) $ mods >>= uncurry (suggests identifier),
+    hideAll <- ("Hide " <> identifier <> " from all occurence imports", concat $ snd <$> result)
+    = result <> [hideAll]
   | otherwise = []
+    where
+      suggests identifier modName s
+        | Just tcM <- mTcM,
+          Just har <- mHar,
+          [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
+          isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
+          title <- "Hide " <> identifier <> " from " <> modName
+         = if modName == "Prelude" && (null $ findImportDeclByModuleName hsmodImports "Prelude")
+              then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
+              else [(title, hideOrRemoveId hsmodImports (T.unpack identifier) (T.unpack modName))]
+        | otherwise = []
 
 hideOrRemoveId :: [LImportDecl GhcPs] -> String -> String -> [Rewrite]
 hideOrRemoveId lImportDecls identifier modName
@@ -220,12 +240,7 @@ isTheSameLine s1 s2
   | otherwise = False
 
 getStartLine :: SrcSpan -> Maybe Int
-getStartLine s
-  | RealSrcSpan s' <- s,
-    startLoc <- realSrcSpanStart s',
-    startLine <- srcLocLine startLoc =
-    Just startLine
-  | otherwise = Nothing
+getStartLine x = srcLocLine . realSrcSpanStart <$> realSpan x
 
 isUnusedImportedId :: TcModuleResult -> HieAstResult -> String -> String -> SrcSpan -> Bool
 isUnusedImportedId
@@ -246,7 +261,7 @@ isUnusedImportedId
       [GRE {..}] <- lookupGlobalRdrEnv rdrEnv occ,
       importedIdentifier <- Right gre_name,
       refs <- M.lookup importedIdentifier rf =
-      maybe True null refs
+      maybe True (null . filter (\(_, IdentifierDetails{..}) -> identInfo == S.singleton Use)) refs
     | otherwise = False
 
 suggestDisableWarning :: ParsedModule -> Maybe T.Text -> Diagnostic -> [(T.Text, [TextEdit])]

From e6f26244156e0db5c337aa9c35621461153c36d9 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Wed, 10 Feb 2021 18:03:43 +0800
Subject: [PATCH 04/10] Remove trailing comma in processed import lists

---
 ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs | 7 +++++--
 ghcide/test/data/hiding/HideFunction.expected.append.E.hs  | 2 +-
 .../data/hiding/HideFunction.expected.append.Prelude.hs    | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
index e7489ff75c..774710ce1f 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
@@ -382,6 +382,8 @@ deleteFromImport (T.pack -> symbol) (L l idecl) llies@(L lieLoc lies) _ =do
         lidecl' = L l $ idecl
             { ideclHiding = Just (False, edited)
             }
+    -- avoid import A (foo,)
+    maybe (pure ()) removeTrailingCommaT $ lastMaybe deletedLies
     when (not (null lies) && null deletedLies) $ do
         transferAnn llies edited id
         addSimpleAnnT edited dp00
@@ -417,6 +419,7 @@ hideImplicitPreludeSymbol symbol (L _ HsModule{..}) = do
         existingDeclSpan = (fmap (predLine, ) . realSpan . getLoc) =<< headMaybe hsmodDecls
     (f, s) <- existingImpSpan <|> existingDeclSpan
     let beg = f $ realSrcSpanEnd s
+        indentation = srcSpanStartCol s
         ran = RealSrcSpan $ mkRealSrcSpan beg beg
     pure $ Rewrite ran $ \df -> do
         let symOcc = mkVarOcc symbol
@@ -426,6 +429,6 @@ hideImplicitPreludeSymbol symbol (L _ HsModule{..}) = do
         -- Re-labeling is needed to reflect annotations correctly
         L _ idecl0 <- liftParseAST @(ImportDecl GhcPs) df $ T.unpack impStmt
         let idecl = L ran idecl0
-        addSimpleAnnT idecl (DP (1, 0))
-            [(G AnnImport, DP (1, 0))]
+        addSimpleAnnT idecl (DP (1, indentation - 1))
+            [(G AnnImport, DP (1, indentation - 1))]
         pure idecl
diff --git a/ghcide/test/data/hiding/HideFunction.expected.append.E.hs b/ghcide/test/data/hiding/HideFunction.expected.append.E.hs
index 94d333b24a..3448baa4f4 100644
--- a/ghcide/test/data/hiding/HideFunction.expected.append.E.hs
+++ b/ghcide/test/data/hiding/HideFunction.expected.append.E.hs
@@ -1,7 +1,7 @@
 module HideFunction where
 
 import AVec (fromList)
-import BVec (fromList,)
+import BVec (fromList)
 import CVec hiding ((++), cons)
 import DVec hiding ((++), cons, snoc)
 import EVec as E
diff --git a/ghcide/test/data/hiding/HideFunction.expected.append.Prelude.hs b/ghcide/test/data/hiding/HideFunction.expected.append.Prelude.hs
index 0b202451f0..78d1cd879b 100644
--- a/ghcide/test/data/hiding/HideFunction.expected.append.Prelude.hs
+++ b/ghcide/test/data/hiding/HideFunction.expected.append.Prelude.hs
@@ -1,7 +1,7 @@
 module HideFunction where
 
 import AVec (fromList)
-import BVec (fromList,)
+import BVec (fromList)
 import CVec hiding ((++), cons)
 import DVec hiding ((++), cons, snoc)
 import EVec as E hiding ((++))

From bea3eb8f97329493a701861824042a5e1ffdc6e4 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Wed, 10 Feb 2021 18:42:23 +0800
Subject: [PATCH 05/10] Add tests

---
 ghcide/test/exe/Main.hs | 177 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)

diff --git a/ghcide/test/exe/Main.hs b/ghcide/test/exe/Main.hs
index 877ddd1f9c..8402e61af7 100644
--- a/ghcide/test/exe/Main.hs
+++ b/ghcide/test/exe/Main.hs
@@ -693,6 +693,7 @@ codeActionTests = testGroup "code actions"
   , removeImportTests
   , extendImportTests
   , suggestImportTests
+  , suggestHideShadowTests
   , suggestImportDisambiguationTests
   , disableWarningTests
   , fixConstructorImportTests
@@ -1586,6 +1587,182 @@ suggestImportDisambiguationTests = testGroup "suggest import disambiguation acti
         k doc actions
     withHideFunction = withTarget ("HideFunction" <.> "hs")
 
+suggestHideShadowTests :: TestTree
+suggestHideShadowTests =
+  testGroup
+    "suggest hide shadow"
+    [ testGroup
+        "single"
+        [ testOneCodeAction
+            "hide unsued"
+            "Hide on from Data.Function"
+            (1, 2)
+            (1, 4)
+            [ "import Data.Function"
+            , "f on = on"
+            , "g on = on"
+            ]
+            [ "import Data.Function hiding (on)"
+            , "f on = on"
+            , "g on = on"
+            ]
+        , testOneCodeAction
+            "delete unsued"
+            "Hide on from Data.Function"
+            (1, 2)
+            (1, 4)
+            [ "import Data.Function ((&), on)"
+            , "f on = on"
+            ]
+            [ "import Data.Function ((&))"
+            , "f on = on"
+            ]
+        , testOneCodeAction
+            "hide operator"
+            "Hide & from Data.Function"
+            (1, 2)
+            (1, 5)
+            [ "import Data.Function"
+            , "f (&) = (&)"
+            ]
+            [ "import Data.Function hiding ((&))"
+            , "f (&) = (&)"
+            ]
+        , testOneCodeAction
+            "remove operator"
+            "Hide & from Data.Function"
+            (1, 2)
+            (1, 5)
+            [ "import Data.Function ((&), on)"
+            , "f (&) = (&)"
+            ]
+            [ "import Data.Function ( on)"
+            , "f (&) = (&)"
+            ]
+        , noCodeAction
+            "don't remove already used"
+            (2, 2)
+            (2, 4)
+            [ "import Data.Function"
+            , "g = on"
+            , "f on = on"
+            ]
+        ]
+    , testGroup
+        "multi"
+        [ testOneCodeAction
+            "hide from B"
+            "Hide ++ from B"
+            (2, 2)
+            (2, 6)
+            [ "import B"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+            [ "import B hiding ((++))"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+        , testOneCodeAction
+            "hide from C"
+            "Hide ++ from C"
+            (2, 2)
+            (2, 6)
+            [ "import B"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+            [ "import B"
+            , "import C hiding ((++))"
+            , "f (++) = (++)"
+            ]
+        ]
+    , testOneCodeAction
+        "hide from Prelude"
+        "Hide ++ from Prelude"
+        (2, 2)
+        (2, 6)
+        [ "import B"
+        , "import C"
+        , "f (++) = (++)"
+        ]
+        [ "import B"
+        , "import C"
+        , "import Prelude hiding ((++))"
+        , "f (++) = (++)"
+        ]
+    , testMultiCodeActions
+        "manual hide all"
+        [ "Hide ++ from Prelude"
+        , "Hide ++ from C"
+        , "Hide ++ from B"
+        ]
+        (2, 2)
+        (2, 6)
+        [ "import B"
+        , "import C"
+        , "f (++) = (++)"
+        ]
+        [ "import B hiding ((++))"
+        , "import C hiding ((++))"
+        , "import Prelude hiding ((++))"
+        , "f (++) = (++)"
+        ]
+    , testOneCodeAction
+        "auto hide all"
+        ""
+        (2, 2)
+        (2, 6)
+        [ "import B"
+        , "import C"
+        , "f (++) = (++)"
+        ]
+        [ "import B hiding ((++))"
+        , "import C ((++))"
+        , "import Prelude hiding ((++))"
+        , "f (++) = (++)"
+        ]
+    ]
+ where
+  testOneCodeAction testName actionName start end origin expected =
+    helper testName start end origin expected $ \cas -> do
+      action <- liftIO $ pickActionWithTitle actionName cas
+      executeCodeAction action
+  noCodeAction testName start end origin =
+    helper testName start end origin origin $ \cas -> do
+      liftIO $ cas @?= []
+  testMultiCodeActions testName actionNames start end origin expected =
+    helper testName start end origin expected $ \cas -> do
+      let r = [ca | (CACodeAction ca) <- cas, ca ^. L.title `elem` actionNames]
+      liftIO $
+        (length r == length actionNames)
+          @? "Expected " <> show actionNames <> ", but got " <> show cas <> " which is not its superset"
+      forM_ r executeCodeAction
+  helper testName (line1, col1) (line2, col2) origin expected k = testSession testName $ do
+    void $ createDoc "B.hs" "haskell" $ T.unlines docB
+    void $ createDoc "C.hs" "haskell" $ T.unlines docC
+    doc <- createDoc "A.hs" "haskell" $ T.unlines (header <> origin)
+    void waitForDiagnostics
+    void (skipManyTill anyMessage message :: Session WorkDoneProgressEndNotification)
+    cas <- getCodeActions doc (Range (Position (line1 + length header) col1) (Position (line2 + length header) col2))
+    void $ k [x | x@(CACodeAction ca) <- cas, "Hide" `T.isPrefixOf` (ca ^. L.title)]
+    contentAfter <- documentContents doc
+    liftIO $ contentAfter @?= T.unlines (header <> expected)
+  header =
+    [ "{-# OPTIONS_GHC -Wname-shadowing #-}"
+    , "module A where"
+    , ""
+    ]
+  -- for multi group
+  docB =
+    [ "module B where"
+    , "(++) = id"
+    ]
+  docC =
+    [ "module C where"
+    , "(++) = id"
+    ]
+
 disableWarningTests :: TestTree
 disableWarningTests =
   testGroup "disable warnings" $

From 78dcf888489c18637f51aee52709d0bb9dc24e54 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Wed, 10 Feb 2021 18:49:35 +0800
Subject: [PATCH 06/10] Make hlint happy

---
 ghcide/src/Development/IDE/Plugin/CodeAction.hs            | 6 +++---
 ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs | 3 ++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction.hs b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
index 7d263b3326..071a8c9dd1 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
@@ -3,7 +3,7 @@
 
 {-# LANGUAGE DuplicateRecordFields #-}
 {-# LANGUAGE CPP                   #-}
-#include "ghc-api-version.h"
+
 
 -- | Go to the definition of a variable.
 module Development.IDE.Plugin.CodeAction
@@ -215,7 +215,7 @@ suggestHideShadow pm@(L _ HsModule {hsmodImports}) mTcM mHar Diagnostic {_messag
           [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
           isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
           title <- "Hide " <> identifier <> " from " <> modName
-         = if modName == "Prelude" && (null $ findImportDeclByModuleName hsmodImports "Prelude")
+         = if modName == "Prelude" && null (findImportDeclByModuleName hsmodImports "Prelude")
               then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
               else [(title, hideOrRemoveId hsmodImports (T.unpack identifier) (T.unpack modName))]
         | otherwise = []
@@ -261,7 +261,7 @@ isUnusedImportedId
       [GRE {..}] <- lookupGlobalRdrEnv rdrEnv occ,
       importedIdentifier <- Right gre_name,
       refs <- M.lookup importedIdentifier rf =
-      maybe True (null . filter (\(_, IdentifierDetails{..}) -> identInfo == S.singleton Use)) refs
+      maybe True (not . any (\(_, IdentifierDetails{..}) -> identInfo == S.singleton Use)) refs
     | otherwise = False
 
 suggestDisableWarning :: ParsedModule -> Maybe T.Text -> Diagnostic -> [(T.Text, [TextEdit])]
diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
index 774710ce1f..86c1defd4d 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction/ExactPrint.hs
@@ -42,6 +42,7 @@ import Development.IDE.Spans.Common
 import Development.IDE.GHC.Error
 import Data.Generics (listify)
 import GHC.Exts (IsList (fromList))
+import Control.Monad.Extra (whenJust)
 
 ------------------------------------------------------------------------------
 
@@ -383,7 +384,7 @@ deleteFromImport (T.pack -> symbol) (L l idecl) llies@(L lieLoc lies) _ =do
             { ideclHiding = Just (False, edited)
             }
     -- avoid import A (foo,)
-    maybe (pure ()) removeTrailingCommaT $ lastMaybe deletedLies
+    whenJust (lastMaybe deletedLies) removeTrailingCommaT
     when (not (null lies) && null deletedLies) $ do
         transferAnn llies edited id
         addSimpleAnnT edited dp00

From 12295e4d3ad659d0f37a64de717bb509e95f6377 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Wed, 10 Feb 2021 18:51:57 +0800
Subject: [PATCH 07/10] Fix macro

---
 ghcide/src/Development/IDE/Plugin/CodeAction.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction.hs b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
index 071a8c9dd1..3fc58bfaf2 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
@@ -3,7 +3,7 @@
 
 {-# LANGUAGE DuplicateRecordFields #-}
 {-# LANGUAGE CPP                   #-}
-
+#include "ghc-api-version.h"
 
 -- | Go to the definition of a variable.
 module Development.IDE.Plugin.CodeAction

From fe62d196d88dba8298497e4ff4d30aa1e635dc67 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Wed, 10 Feb 2021 20:50:43 +0800
Subject: [PATCH 08/10] Fix a test suite

---
 ghcide/test/exe/Main.hs | 90 ++++++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 45 deletions(-)

diff --git a/ghcide/test/exe/Main.hs b/ghcide/test/exe/Main.hs
index 8402e61af7..b21492f854 100644
--- a/ghcide/test/exe/Main.hs
+++ b/ghcide/test/exe/Main.hs
@@ -1676,51 +1676,51 @@ suggestHideShadowTests =
             , "import C hiding ((++))"
             , "f (++) = (++)"
             ]
-        ]
-    , testOneCodeAction
-        "hide from Prelude"
-        "Hide ++ from Prelude"
-        (2, 2)
-        (2, 6)
-        [ "import B"
-        , "import C"
-        , "f (++) = (++)"
-        ]
-        [ "import B"
-        , "import C"
-        , "import Prelude hiding ((++))"
-        , "f (++) = (++)"
-        ]
-    , testMultiCodeActions
-        "manual hide all"
-        [ "Hide ++ from Prelude"
-        , "Hide ++ from C"
-        , "Hide ++ from B"
-        ]
-        (2, 2)
-        (2, 6)
-        [ "import B"
-        , "import C"
-        , "f (++) = (++)"
-        ]
-        [ "import B hiding ((++))"
-        , "import C hiding ((++))"
-        , "import Prelude hiding ((++))"
-        , "f (++) = (++)"
-        ]
-    , testOneCodeAction
-        "auto hide all"
-        ""
-        (2, 2)
-        (2, 6)
-        [ "import B"
-        , "import C"
-        , "f (++) = (++)"
-        ]
-        [ "import B hiding ((++))"
-        , "import C ((++))"
-        , "import Prelude hiding ((++))"
-        , "f (++) = (++)"
+        , testOneCodeAction
+            "hide from Prelude"
+            "Hide ++ from Prelude"
+            (2, 2)
+            (2, 6)
+            [ "import B"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+            [ "import B"
+            , "import C"
+            , "import Prelude hiding ((++))"
+            , "f (++) = (++)"
+            ]
+        , testMultiCodeActions
+            "manual hide all"
+            [ "Hide ++ from Prelude"
+            , "Hide ++ from C"
+            , "Hide ++ from B"
+            ]
+            (2, 2)
+            (2, 6)
+            [ "import B"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+            [ "import B hiding ((++))"
+            , "import C hiding ((++))"
+            , "import Prelude hiding ((++))"
+            , "f (++) = (++)"
+            ]
+        , testOneCodeAction
+            "auto hide all"
+            "Hide ++ from all occurence imports"
+            (2, 2)
+            (2, 6)
+            [ "import B"
+            , "import C"
+            , "f (++) = (++)"
+            ]
+            [ "import B hiding ((++))"
+            , "import C ((++))"
+            , "import Prelude hiding ((++))"
+            , "f (++) = (++)"
+            ]
         ]
     ]
  where

From bfc2b31ba957df18af8d95c236d2f4aa9c560c66 Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Thu, 11 Feb 2021 09:30:22 +0800
Subject: [PATCH 09/10] Update test

---
 ghcide/test/exe/Main.hs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/ghcide/test/exe/Main.hs b/ghcide/test/exe/Main.hs
index b21492f854..33c7322de9 100644
--- a/ghcide/test/exe/Main.hs
+++ b/ghcide/test/exe/Main.hs
@@ -1606,6 +1606,17 @@ suggestHideShadowTests =
             , "f on = on"
             , "g on = on"
             ]
+        , testOneCodeAction
+            "extend hiding unsued"
+            "Hide on from Data.Function"
+            (1, 2)
+            (1, 4)
+            [ "import Data.Function hiding ((&))"
+            , "f on = on"
+            ]
+            [ "import Data.Function hiding (on, (&))"
+            , "f on = on"
+            ]
         , testOneCodeAction
             "delete unsued"
             "Hide on from Data.Function"
@@ -1717,7 +1728,7 @@ suggestHideShadowTests =
             , "f (++) = (++)"
             ]
             [ "import B hiding ((++))"
-            , "import C ((++))"
+            , "import C hiding ((++))"
             , "import Prelude hiding ((++))"
             , "f (++) = (++)"
             ]

From 439a09d841cfa0458cc540922b4ca656a88798cb Mon Sep 17 00:00:00 2001
From: Potato Hatsue <1793913507@qq.com>
Date: Thu, 11 Feb 2021 14:29:32 +0800
Subject: [PATCH 10/10] Minor refactor

---
 .../src/Development/IDE/Plugin/CodeAction.hs  | 50 ++++++++-----------
 1 file changed, 21 insertions(+), 29 deletions(-)

diff --git a/ghcide/src/Development/IDE/Plugin/CodeAction.hs b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
index 3fc58bfaf2..67a1b5cf0f 100644
--- a/ghcide/src/Development/IDE/Plugin/CodeAction.hs
+++ b/ghcide/src/Development/IDE/Plugin/CodeAction.hs
@@ -190,14 +190,13 @@ findDeclContainingLoc loc = find (\(L l _) -> loc `isInsideSrcSpan` l)
 --  imported from ‘Data.ByteString’ at B.hs:6:1-22
 --  imported from ‘Data.ByteString.Lazy’ at B.hs:8:1-27
 --  imported from ‘Data.Text’ at B.hs:7:1-16
-
 suggestHideShadow :: ParsedSource -> Maybe TcModuleResult -> Maybe HieAstResult -> Diagnostic -> [(T.Text, [Rewrite])]
 suggestHideShadow pm@(L _ HsModule {hsmodImports}) mTcM mHar Diagnostic {_message, _range}
   | Just [identifier, modName, s] <-
       matchRegexUnifySpaces
         _message
-        "This binding for ‘([^`]+)’ shadows the existing binding imported from ‘([^`]+)’ at ([^ ]*)"
-    = suggests identifier modName s
+        "This binding for ‘([^`]+)’ shadows the existing binding imported from ‘([^`]+)’ at ([^ ]*)" =
+    suggests identifier modName s
   | Just [identifier] <-
       matchRegexUnifySpaces
         _message
@@ -205,27 +204,21 @@ suggestHideShadow pm@(L _ HsModule {hsmodImports}) mTcM mHar Diagnostic {_messag
     Just matched <- allMatchRegexUnifySpaces _message "imported from ‘([^’]+)’ at ([^ ]*)",
     mods <- [(modName, s) | [_, modName, s] <- matched],
     result <- nubOrdBy (compare `on` fst) $ mods >>= uncurry (suggests identifier),
-    hideAll <- ("Hide " <> identifier <> " from all occurence imports", concat $ snd <$> result)
-    = result <> [hideAll]
+    hideAll <- ("Hide " <> identifier <> " from all occurence imports", concat $ snd <$> result) =
+    result <> [hideAll]
   | otherwise = []
-    where
-      suggests identifier modName s
-        | Just tcM <- mTcM,
-          Just har <- mHar,
-          [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
-          isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
-          title <- "Hide " <> identifier <> " from " <> modName
-         = if modName == "Prelude" && null (findImportDeclByModuleName hsmodImports "Prelude")
-              then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
-              else [(title, hideOrRemoveId hsmodImports (T.unpack identifier) (T.unpack modName))]
-        | otherwise = []
-
-hideOrRemoveId :: [LImportDecl GhcPs] -> String -> String -> [Rewrite]
-hideOrRemoveId lImportDecls identifier modName
-  | Just decl <- findImportDeclByModuleName lImportDecls modName =
-    [hideSymbol identifier decl]
-  | otherwise =
-    []
+  where
+    suggests identifier modName s
+      | Just tcM <- mTcM,
+        Just har <- mHar,
+        [s'] <- [x | (x, "") <- readSrcSpan $ T.unpack s],
+        isUnusedImportedId tcM har (T.unpack identifier) (T.unpack modName) (RealSrcSpan s'),
+        mDecl <- findImportDeclByModuleName hsmodImports $ T.unpack modName,
+        title <- "Hide " <> identifier <> " from " <> modName =
+        if modName == "Prelude" && null mDecl
+          then [(title, maybeToList $ hideImplicitPreludeSymbol (T.unpack identifier) pm)]
+          else maybeToList $ (title,) . pure . hideSymbol (T.unpack identifier) <$> mDecl
+      | otherwise = []
 
 findImportDeclByModuleName :: [LImportDecl GhcPs] -> String -> Maybe (LImportDecl GhcPs)
 findImportDeclByModuleName decls modName = flip find decls $ \case
@@ -238,14 +231,13 @@ isTheSameLine s1 s2
     Just sl2 <- getStartLine s2 =
     sl1 == sl2
   | otherwise = False
-
-getStartLine :: SrcSpan -> Maybe Int
-getStartLine x = srcLocLine . realSrcSpanStart <$> realSpan x
+  where
+    getStartLine x = srcLocLine . realSrcSpanStart <$> realSpan x
 
 isUnusedImportedId :: TcModuleResult -> HieAstResult -> String -> String -> SrcSpan -> Bool
 isUnusedImportedId
   TcModuleResult {tmrTypechecked = TcGblEnv {tcg_imports = ImportAvails {imp_mods}}}
-  HAR {refMap = rf}
+  HAR {refMap}
   identifier
   modName
   importSpan
@@ -260,8 +252,8 @@ isUnusedImportedId
           ],
       [GRE {..}] <- lookupGlobalRdrEnv rdrEnv occ,
       importedIdentifier <- Right gre_name,
-      refs <- M.lookup importedIdentifier rf =
-      maybe True (not . any (\(_, IdentifierDetails{..}) -> identInfo == S.singleton Use)) refs
+      refs <- M.lookup importedIdentifier refMap =
+      maybe True (not . any (\(_, IdentifierDetails {..}) -> identInfo == S.singleton Use)) refs
     | otherwise = False
 
 suggestDisableWarning :: ParsedModule -> Maybe T.Text -> Diagnostic -> [(T.Text, [TextEdit])]