format: filter out default imports before rendering

compiler/src/Gren/Format/Normalize.hs

@@ -0,0 +1,65 @@
+{-# LANGUAGE MagicHash #-}
+
+-- | This module is the "normalization" phase that transforms the raw source AST
+-- into an AST ready for rendering back into a text representation.
+--
+-- This is simply a place to put "formatting" logic that doesn't really make sense
+-- as a responsibility for the code that is rendering the AST into text.
+module Gren.Format.Normalize (normalize) where
+
+import AST.Source qualified as Src
+import Data.Map (Map)
+import Data.Map qualified as Map
+import Data.Maybe (mapMaybe)
+import Data.Name (Name)
+import Gren.Compiler.Imports qualified
+import Reporting.Annotation qualified as A
+
+normalize :: Src.Module -> Src.Module
+normalize module_ =
+  module_
+    { Src._imports = mapMaybe removeDefaultImports $ Src._imports module_
+    }
+
+removeDefaultImports :: Src.Import -> Maybe Src.Import
+removeDefaultImports import_@(Src.Import name alias exposing) =
+  case Map.lookup (A.toValue name) defaultImports of
+    Just (Src.Import _ defAlias defExposing) ->
+      if alias == defAlias && exposingEq exposing defExposing
+        then Nothing
+        else Just import_
+    Nothing -> Just import_
+
+defaultImports :: Map Name Src.Import
+defaultImports =
+  Map.fromList $ fmap (\import_ -> (Src.getImportName import_, import_)) Gren.Compiler.Imports.defaults
+
+exposingEq :: Src.Exposing -> Src.Exposing -> Bool
+exposingEq Src.Open Src.Open = True
+exposingEq (Src.Explicit a) (Src.Explicit b) =
+  fmap stripRegionsExposed a == fmap stripRegionsExposed b
+exposingEq _ _ = False
+
+data SimpleExposed
+  = Lower Name
+  | Upper Name SimplePrivacy
+  | Operator Name
+  deriving (Eq)
+
+data SimplePrivacy
+  = Public
+  | Private
+  deriving (Eq)
+
+stripRegionsExposed :: Src.Exposed -> SimpleExposed
+stripRegionsExposed exposed =
+  case exposed of
+    Src.Lower (A.At _ name) -> Lower name
+    Src.Upper (A.At _ name) priv -> Upper name (stripRegionsPrivacy priv)
+    Src.Operator _ name -> Operator name
+
+stripRegionsPrivacy :: Src.Privacy -> SimplePrivacy
+stripRegionsPrivacy priv =
+  case priv of
+    Src.Public _ -> Public
+    Src.Private -> Private

gren.cabal

@@ -95,6 +95,7 @@ Common gren-common
         Gren.Docs
         Gren.Float
         Gren.Format
+        Gren.Format.Normalize
         Gren.Interface
         Gren.Kernel
         Gren.Licenses

terminal/src/Format.hs

@@ -15,6 +15,7 @@ import Data.NonEmptyList qualified as NE
 import Directories qualified as Dirs
 import File qualified
 import Gren.Format qualified as Format
+import Gren.Format.Normalize qualified as Normalize
 import Gren.Outline qualified as Outline
 import Parse.Module qualified as Parse
 import Reporting qualified
@@ -173,4 +174,4 @@ formatByteString original =
       -- TODO: report error
       Nothing
     Right ast ->
-      Just (Format.toByteStringBuilder ast)
+      Just (Format.toByteStringBuilder $ Normalize.normalize ast)