Do not place Prelude at the end with NoImplicitPrelude (#1216)

Co-authored-by: Mark Karpov <markkarpov92@gmail.com>

Author: joaosreis

CHANGELOG.md

@@ -6,6 +6,10 @@
 * Fixed preservation of the position of comments around the `where` keyword.
   [Issue 784](https://github.com/tweag/ormolu/issues/784).
 
+* Do not sort `Prelude` to the end of the import list when the
+  `NoImplicitPrelude` extension is enabled; instead sort it like any other
+  import. [Issue 1189](https://github.com/tweag/ormolu/issues/1189). Cherry-picked [mrkkrp/ormolu@e67dbfe](https://github.com/mrkkrp/ormolu/commit/e67dbfe2faca57769755bb3d2240c0f6cc07a0a5).
+
 ## Ormolu 0.8.1.1
 
 * Add missing braces for case expressions in single‑line do blocks. [Issue

data/examples/import/implicit-prelude-package-out.hs

@@ -0,0 +1,7 @@
+{-# LANGUAGE PackageImports #-}
+
+import "base" Control.Applicative (Alternative, (<|>))
+import "base" Data.Maybe (Maybe (Nothing), maybe)
+import "base" System.IO (IO)
+import "yaya" Yaya.Fold (ana, cata)
+import "base" Prelude ((+))

data/examples/import/implicit-prelude-package.hs

@@ -0,0 +1,7 @@
+{-# LANGUAGE PackageImports #-}
+
+import "base" System.IO (IO)
+import "base" Prelude ((+))
+import "yaya" Yaya.Fold (ana, cata)
+import "base" Control.Applicative (Alternative, (<|>))
+import "base" Data.Maybe (Maybe (Nothing), maybe)

data/examples/import/no-implicit-prelude-out.hs

@@ -0,0 +1,6 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
+import Control.Applicative (Alternative, (<|>))
+import Data.Maybe (Maybe (Nothing), maybe)
+import Prelude ((+))
+import System.IO (IO)

data/examples/import/no-implicit-prelude-package-out.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE PackageImports #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+import "base" Control.Applicative (Alternative, (<|>))
+import "base" Data.Maybe (Maybe (Nothing), maybe)
+import "base" Prelude ((+))
+import "base" System.IO (IO)
+import "yaya" Yaya.Fold (ana, cata)

data/examples/import/no-implicit-prelude-package.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE PackageImports #-}
+
+import "base" System.IO (IO)
+import "base" Prelude ((+))
+import "yaya" Yaya.Fold (ana, cata)
+import "base" Control.Applicative (Alternative, (<|>))
+import "base" Data.Maybe (Maybe (Nothing), maybe)

data/examples/import/no-implicit-prelude.hs

@@ -0,0 +1,6 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
+import System.IO (IO)
+import Prelude ((+))
+import Control.Applicative (Alternative, (<|>))
+import Data.Maybe (Maybe (Nothing), maybe)

src/Ormolu/Imports.hs

@@ -27,12 +27,12 @@ import GHC.Types.SrcLoc
 import Ormolu.Utils (notImplemented, showOutputable)
 
 -- | Sort and normalize imports.
-normalizeImports :: [LImportDecl GhcPs] -> [LImportDecl GhcPs]
-normalizeImports =
+normalizeImports :: Bool -> [LImportDecl GhcPs] -> [LImportDecl GhcPs]
+normalizeImports implicitPrelude =
   fmap snd
     . M.toAscList
     . M.fromListWith combineImports
-    . fmap (\x -> (importId x, g x))
+    . fmap (\x -> (importId implicitPrelude x, g x))
   where
     g :: LImportDecl GhcPs -> LImportDecl GhcPs
     g (L l ImportDecl {..}) =
@@ -118,8 +118,8 @@ instance Ord ImportListInterpretationOrd where
       toBool EverythingBut = True
 
 -- | Obtain an 'ImportId' for a given import.
-importId :: LImportDecl GhcPs -> ImportId
-importId (L _ ImportDecl {..}) =
+importId :: Bool -> LImportDecl GhcPs -> ImportId
+importId implicitPrelude (L _ ImportDecl {..}) =
   ImportId
     { importIsPrelude = isPrelude,
       importIdName = moduleName,
@@ -135,7 +135,7 @@ importId (L _ ImportDecl {..}) =
       importLevel = importLevelOf ideclLevelSpec
     }
   where
-    isPrelude = moduleNameString moduleName == "Prelude"
+    isPrelude = implicitPrelude && moduleNameString moduleName == "Prelude"
     moduleName = unLoc ideclName
     importLevelOf = \case
       LevelStylePre l -> Just (ImportDeclLevelOrd l)

src/Ormolu/Parser.hs

@@ -143,12 +143,13 @@ parseModuleSnippet Config {..} modFixityMap dynFlags path rawInput = liftIO $ do
       parser = case cfgSourceType of
         ModuleSource -> GHC.parseModule
         SignatureSource -> GHC.parseSignature
+      implicitPrelude = EnumSet.member ImplicitPrelude (GHC.extensionFlags dynFlags)
       r = case runParser parser dynFlags path input of
         GHC.PFailed pstate ->
           case pStateErrors pstate of
             Just err -> Left err
             Nothing -> error "PFailed does not have an error"
-        GHC.POk pstate (L _ (normalizeModule -> hsModule)) ->
+        GHC.POk pstate (L _ (normalizeModule implicitPrelude -> hsModule)) ->
           case pStateErrors pstate of
             -- Some parse errors (pattern/arrow syntax in expr context)
             -- do not cause a parse error, but they are replaced with "_"
@@ -173,8 +174,8 @@ parseModuleSnippet Config {..} modFixityMap dynFlags path rawInput = liftIO $ do
 
 -- | Normalize a 'HsModule' by sorting its import\/export lists, dropping
 -- blank comments, etc.
-normalizeModule :: HsModule GhcPs -> HsModule GhcPs
-normalizeModule hsmod =
+normalizeModule :: Bool -> HsModule GhcPs -> HsModule GhcPs
+normalizeModule implicitPrelude hsmod =
   everywhere
     ( mkT dropBlankTypeHaddocks
         `extT` dropBlankDataDeclHaddocks
@@ -183,7 +184,7 @@ normalizeModule hsmod =
     )
     hsmod
       { hsmodImports =
-          normalizeImports (hsmodImports hsmod),
+          normalizeImports implicitPrelude (hsmodImports hsmod),
         hsmodDecls =
           filter (not . isBlankDocD . unLoc) (hsmodDecls hsmod),
         hsmodExt =