Add support for post qualified import formatting (more cases) (#372)

* Add support for post qualified import formatting.

Adds an option to use post qualified module imports.

Related to #284
Resolves #334

* Add failing test cases for post qualified import formatting.
  
Related to #284 and #334

* Fix imports test case 33 - 'qualified' goes before imported names

* Consolidate import module name logic

Co-authored-by: Jim McStanton <jim@jhmcstanton.com>

Author: akrmn

data/stylish-haskell.yaml

@@ -275,21 +275,25 @@ steps:
       # Default: false
       space_surround: false
 
-      # Enabling this argument will use the new GHC lib parse to format imports.
+      # Post qualify option moves any qualifies found in import declarations
+      # to the end of the declaration. This also adjust padding for any
+      # unqualified import declarations.
       #
-      # This currently assumes a few things, it will assume that you want post
-      # qualified imports. It is also not as feature complete as the old
-      # imports formatting.
+      # - true: Qualified as <module name> is moved to the end of the
+      #   declaration.
       #
-      # It does not remove redundant lines or merge lines. As such, the full
-      # feature scope is still pending.
+      #   > import Data.Bar
+      #   > import Data.Foo qualified as F
       #
-      # It _is_ however, a fine alternative if you are using features that are
-      # not parseable by haskell src extensions and you're comfortable with the
-      # presets.
+      # - false: Qualified remains in the default location and unqualified
+      #   imports are padded to align with qualified imports.
+      #
+      #   > import           Data.Bar
+      #   > import qualified Data.Foo as F
       #
       # Default: false
-      ghc_lib_parser: false
+      post_qualify: false
+
 
   # Language pragmas
   - language_pragmas:

lib/Language/Haskell/Stylish/Config.hs

@@ -289,6 +289,7 @@ parseImports config o = fmap (Imports.step columns) $ Imports.Options
       <*> (o A..:? "list_padding" >>= maybe (pure $ def Imports.listPadding) parseListPadding)
       <*> o A..:? "separate_lists" A..!= def Imports.separateLists
       <*> o A..:? "space_surround" A..!= def Imports.spaceSurround
+      <*> o A..:? "post_qualify" A..!= def Imports.postQualified
   where
     def f = f Imports.defaultOptions
 

lib/Language/Haskell/Stylish/Step/Imports.hs

@@ -61,6 +61,7 @@ data Options = Options
     , listPadding     :: ListPadding
     , separateLists   :: Bool
     , spaceSurround   :: Bool
+    , postQualified   :: Bool
     } deriving (Eq, Show)
 
 defaultOptions :: Options
@@ -73,6 +74,7 @@ defaultOptions = Options
     , listPadding     = LPConstant 4
     , separateLists   = True
     , spaceSurround   = False
+    , postQualified   = False
     }
 
 data ListPadding
@@ -143,8 +145,8 @@ formatImports
     -> NonEmpty (Located Import) -> Lines
 formatImports maxCols options m moduleStats rawGroup =
   runPrinter_ (PrinterConfig maxCols) [] m do
-  let 
-     
+  let
+
     group
       = NonEmpty.sortWith unLocated rawGroup
       & mergeImports
@@ -177,25 +179,31 @@ printQualified Options{..} padNames stats (L _ decl) = do
 
   when (isSafe decl) (putText "safe" >> space)
 
-  case (isQualified decl, isAnyQualified stats) of
-    (True, _) -> putText "qualified" >> space
-    (_, True) -> putText "         " >> space
-    _         -> pure ()
-
-  moduleNamePosition <- length <$> getCurrentLine
-  forM_ (ideclPkgQual decl') $ \pkg -> putText (stringLiteral pkg) >> space
-  putText (moduleName decl)
-
-  -- Only print spaces if something follows.
-  when padNames $
-    when (isJust (ideclAs decl') || isHiding decl ||
-            not (null $ ideclHiding decl')) $
-      putText $
-        replicate (isLongestImport stats - importModuleNameLength decl) ' '
+  let
+    module_ = do
+      moduleNamePosition <- length <$> getCurrentLine
+      forM_ (ideclPkgQual decl') $ \pkg -> putText (stringLiteral pkg) >> space
+      putText (moduleName decl)
+      -- Only print spaces if something follows.
+      when padNames $
+        when (isJust (ideclAs decl') || isHiding decl ||
+                not (null $ ideclHiding decl')) $
+          putText $
+            replicate (isLongestImport stats - importModuleNameLength decl) ' '
+      pure moduleNamePosition
+
+  moduleNamePosition <-
+    case (postQualified, isQualified decl, isAnyQualified stats) of
+      (False, True , _   ) -> putText "qualified" *> space *> module_
+      (False, _    , True) -> putText "         " *> space *> module_
+      (True , True , _   ) -> module_ <* space <* putText "qualified"
+      _                    -> module_
 
   beforeAliasPosition <- length <$> getCurrentLine
-  forM_ (ideclAs decl') \(L _ name) ->
+
+  forM_ (ideclAs decl') \(L _ name) -> do
     space >> putText "as" >> space >> putText (moduleNameString name)
+
   afterAliasPosition <- length <$> getCurrentLine
 
   when (isHiding decl) (space >> putText "hiding")