Custom-setups completion in cabal files (#4848)

* Custom-setups completion in cabal files

* Common completer

Author: vidit-od

plugins/hls-cabal-plugin/src/Ide/Plugin/Cabal/Completion/Data.hs

@@ -88,7 +88,8 @@ stanzaKeywordMap =
       ("common", libExecTestBenchCommons Library),
       ("common", libExecTestBenchCommons Common),
       ("flag", flagFields),
-      ("source-repository", sourceRepositoryFields)
+      ("source-repository", sourceRepositoryFields),
+      ("custom-setup", customSetupFields)
     ]
 
 libraryFields :: Map KeyWordName Completer
@@ -180,7 +181,7 @@ libExecTestBenchCommons st =
       ("hs-source-dirs:", directoryCompleter),
       ("default-extensions:", constantCompleter $ map (T.pack . prettyShow) allExtensions),
       ("other-extensions:", constantCompleter $ map (T.pack . prettyShow) allExtensions),
-      ("default-language:", constantCompleter ["GHC2021", "Haskell2010", "Haskell98"]),
+      ("default-language:", defaultLanguageCompleter),
       ("other-languages:", noopCompleter),
       ("build-tool-depends:", noopCompleter),
       ("buildable:", constantCompleter ["True", "False"]),
@@ -236,6 +237,15 @@ libExecTestBenchCommons st =
         -- but not have erased the "common" stanza.
         noopCompleter
 
+customSetupFields :: Map KeyWordName Completer
+customSetupFields =
+  Map.fromList
+    [ ("setup-depends:", noopCompleter)
+    , ("build-depends:", noopCompleter)
+    , ("build-tools:", noopCompleter)
+    , ("default-language:", defaultLanguageCompleter)
+    ]
+
 -- | Returns all possible language extensions including disabled ones.
 allExtensions :: [Extension]
 allExtensions =
@@ -249,6 +259,10 @@ allExtensions =
     )
     knownExtensions
 
+-- | Returns all possible default languages
+defaultLanguageCompleter :: Completer
+defaultLanguageCompleter = constantCompleter $ map (T.pack . prettyShow) knownLanguages
+
 -- | Contains a map of the most commonly used licenses, weighted by their popularity.
 --
 --  The data was extracted by Kleidukos from the alternative hackage frontend flora.pm.
@@ -309,3 +323,4 @@ weightedLicenseNames =
 
 ghcOptions :: [T.Text]
 ghcOptions = map T.pack $ flagsForCompletion False
+