support selection range lsp feature

plugins/hls-selection-range-plugin/src/Ide/Plugin/SelectionRange/ASTPreProcess.hs

@@ -7,8 +7,10 @@ module Ide.Plugin.SelectionRange.ASTPreProcess
     ) where
 
 import           Control.Monad.Reader            (Reader, asks)
-import           Data.Foldable                   (find, foldl')
-import           Data.List                       (foldl1', groupBy)
+import           Data.Foldable                   (find, foldl', foldl1)
+import           Data.List                       (groupBy)
+import           Data.List.NonEmpty              (NonEmpty)
+import qualified Data.List.NonEmpty              as NonEmpty
 import qualified Data.Map.Strict                 as Map
 import           Data.Maybe                      (mapMaybe)
 import qualified Data.Set                        as Set
@@ -61,19 +63,18 @@ mergeImports node = pure $ node { nodeChildren = children }
         . nodeChildren $ node
 
     merge :: [HieAST a] -> Maybe (HieAST a)
-    merge []  = Nothing
-    merge [x] = Just x
-    merge xs  = createVirtualNode xs
+    merge []     = Nothing
+    merge [x]    = Just x
+    merge (x:xs) = Just $ createVirtualNode (x NonEmpty.:| xs)
 
 nodeIsImport :: HieAST a -> Bool
 nodeIsImport = isAnnotationInAstNode ("ImportDecl", "ImportDecl")
 
-createVirtualNode :: [HieAST a] -> Maybe (HieAST a)
-createVirtualNode [] = Nothing
-createVirtualNode children = Just $ mkAstNode (NodeInfo mempty mempty mempty) span' children
+createVirtualNode :: NonEmpty (HieAST a) -> HieAST a
+createVirtualNode children = mkAstNode (NodeInfo mempty mempty mempty) span' (NonEmpty.toList children)
   where
     span' :: RealSrcSpan
-    span' = foldl1' combineRealSrcSpans . fmap nodeSpan $ children
+    span' = foldl1 combineRealSrcSpans . fmap nodeSpan $ children
 
 {-|
 Combine type signature with variable definition under a new parent node, if the signature is placed right before the
@@ -107,7 +108,7 @@ mergeAdjacentSigDef refMap (n1, n2) = do
     -- Does that identifier appear in the second AST node as a definition? If so, we combines the two nodes.
     refs <- Map.lookup typeSigId refMap
     if any (isIdentADef (nodeSpan n2)) refs
-    then createVirtualNode [n1, n2]
+    then pure . createVirtualNode $ n1 NonEmpty.:| [n2]
     else Nothing
   where
     checkAnnotation :: Maybe ()