Fix duplicated completions (#837)

Co-authored-by: Vitalii Ovechkin <ovechkinve@yandex-team.ru>

src/Development/IDE/Plugin/Completions/Logic.hs

@@ -482,9 +482,10 @@ getCompletions ideOpts CC { allModNamesAsNS, unqualCompls, qualCompls, importabl
         | "{-# " `T.isPrefixOf` fullLine
         = filtPragmaCompls (pragmaSuffix fullLine)
         | otherwise
-        = filtModNameCompls ++ map (toggleSnippets caps withSnippets
-                                      . mkCompl ideOpts . stripAutoGenerated) filtCompls
-                            ++ filtKeywordCompls
+        = let uniqueFiltCompls = nubOrdOn insertText filtCompls
+          in filtModNameCompls ++ map (toggleSnippets caps withSnippets
+                                         . mkCompl ideOpts . stripAutoGenerated) uniqueFiltCompls
+                               ++ filtKeywordCompls
 
   return result
 

test/exe/Main.hs

@@ -2660,6 +2660,12 @@ nonLocalCompletionTests =
       ["{-# OPTIONS_GHC -Wunused-binds #-}", "module A () where", "f = Prelude.hea"]
       (Position 2 15)
       [ ("head", CiFunction, True, True)
+      ],
+    completionTest
+      "duplicate import"
+      ["module A where", "import Data.List", "import Data.List", "f = perm"]
+      (Position 3 8)
+      [ ("permutations", CiFunction, False, False)
       ]
   ]