Merge pull request #123 from phadej/empty-list-align

Empty list align

4 files changed, 78 insertions, 19 deletions

diff --git a/data/stylish-haskell.yaml b/data/stylish-haskell.yaml
index 2398e6b..b8e569d 100644
--- a/data/stylish-haskell.yaml
+++ b/data/stylish-haskell.yaml
@@ -87,6 +87,19 @@ steps:
       # Default: inline
       long_list_align: inline
 
+      # Align empty list (importing instances)
+      #
+      # Empty list align has following options
+      #
+      # - inherit: inherit list_align setting
+      #
+      # - right_after: () is right after the module name:
+      #
+      #   > import Vector.Instances ()
+      #
+      # Default: inherit
+      empty_list_align: inherit
+
       # List padding determines indentation of import list on lines after import.
       # This option affects 'list_align' and 'long_list_align'.
       list_padding: 4
diff --git a/lib/Language/Haskell/Stylish/Config.hs b/lib/Language/Haskell/Stylish/Config.hs
index d14e1be..e551d71 100644
--- a/lib/Language/Haskell/Stylish/Config.hs
+++ b/lib/Language/Haskell/Stylish/Config.hs
@@ -187,6 +187,8 @@ parseImports config o = Imports.step
         <*> (o A..:? "long_list_align"
             >>= parseEnum longListAligns Imports.Inline)
         -- Note that padding has to be at least 1. Default is 4.
+        <*> (o A..:? "empty_list_align"
+            >>= parseEnum emptyListAligns Imports.Inherit)
         <*> (maybe 4 (max 1) <$> o A..:? "list_padding")
         <*> o A..:? "separate_lists" A..!= True)
   where
@@ -210,6 +212,11 @@ parseImports config o = Imports.step
         , ("multiline",          Imports.Multiline)
         ]
 
+    emptyListAligns =
+        [ ("inherit", Imports.Inherit)
+        , ("right_after", Imports.RightAfter)
+        ]
+
 
 --------------------------------------------------------------------------------
 parseLanguagePragmas :: Config -> A.Object -> A.Parser Step
diff --git a/lib/Language/Haskell/Stylish/Step/Imports.hs b/lib/Language/Haskell/Stylish/Step/Imports.hs
index ac84933..00ca9b7 100644
--- a/lib/Language/Haskell/Stylish/Step/Imports.hs
+++ b/lib/Language/Haskell/Stylish/Step/Imports.hs
@@ -5,12 +5,14 @@ module Language.Haskell.Stylish.Step.Imports
     , ImportAlign (..)
     , ListAlign (..)
     , LongListAlign (..)
+    , EmptyListAlign (..)
     , step
     ) where
 
 
 --------------------------------------------------------------------------------
 import           Control.Arrow                   ((&&&))
+import           Control.Monad                   (void)
 import           Data.Char                       (toLower)
 import           Data.List                       (intercalate, sortBy)
 import           Data.Maybe                      (isJust, maybeToList)
@@ -26,11 +28,12 @@ import           Language.Haskell.Stylish.Util
 
 --------------------------------------------------------------------------------
 data Align = Align
-    { importAlign   :: ImportAlign
-    , listAlign     :: ListAlign
-    , longListAlign :: LongListAlign
-    , listPadding   :: Int
-    , separateLists :: Bool
+    { importAlign    :: ImportAlign
+    , listAlign      :: ListAlign
+    , longListAlign  :: LongListAlign
+    , emptyListAlign :: EmptyListAlign
+    , listPadding    :: Int
+    , separateLists  :: Bool
     }
     deriving (Eq, Show)
 
@@ -47,6 +50,11 @@ data ListAlign
     | AfterAlias
     deriving (Eq, Show)
 
+data EmptyListAlign
+    = Inherit
+    | RightAfter
+    deriving (Eq, Show)
+
 data LongListAlign
     = Inline
     | InlineWithBreak
@@ -136,13 +144,16 @@ prettyImportSpec separate = prettyImportSpec'
 --------------------------------------------------------------------------------
 prettyImport :: (Ord l, Show l) =>
     Int -> Align -> Bool -> Bool -> Int -> H.ImportDecl l -> [String]
-prettyImport columns Align{..} padQualified padName longest imp =
-    case longListAlign of
+prettyImport columns Align{..} padQualified padName longest imp
+    | (void `fmap` H.importSpecs imp) == emptyImportSpec = emptyWrap
+    | otherwise = case longListAlign of
         Inline            -> inlineWrap
         InlineWithBreak   -> longListWrapper inlineWrap inlineWithBreakWrap
         InlineToMultiline -> longListWrapper inlineWrap inlineToMultilineWrap
         Multiline         -> longListWrapper inlineWrap multilineWrap
   where
+    emptyImportSpec = Just (H.ImportSpecList () False [])
+
     longListWrapper shortWrap longWrap
         | listAlign == NewLine
         || length shortWrap > 1
@@ -150,6 +161,10 @@ prettyImport columns Align{..} padQualified padName longest imp =
             = longWrap
         | otherwise = shortWrap
 
+    emptyWrap = case emptyListAlign of
+        Inherit -> inlineWrap
+        RightAfter -> [paddedNoSpecBase ++ " ()"]
+
     inlineWrap = inlineWrapper
         $ mapSpecs
         $ withInit (++ ",")
diff --git a/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs b/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
index 4ed0bd6..4ebc050 100644
--- a/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
+++ b/tests/Language/Haskell/Stylish/Step/Imports/Tests.hs
@@ -17,7 +17,7 @@ import           Language.Haskell.Stylish.Tests.Util
 
 --------------------------------------------------------------------------------
 defaultAlign :: Align
-defaultAlign = Align Global AfterAlias Inline 4 True
+defaultAlign = Align Global AfterAlias Inline Inherit 4 True
 
 
 --------------------------------------------------------------------------------
@@ -45,6 +45,7 @@ tests = testGroup "Language.Haskell.Stylish.Step.Imports.Tests"
     , testCase "case 16" case16
     , testCase "case 17" case17
     , testCase "case 18" case18
+    , testCase "case 19" case19
     ]
 
 
@@ -184,7 +185,7 @@ case07 = expected @=? testStep (step 80 $ fromImportAlign File) input'
 --------------------------------------------------------------------------------
 case08 :: Assertion
 case08 = expected
-    @=? testStep (step 80 $ Align Global WithAlias Inline 4 True) input
+    @=? testStep (step 80 $ Align Global WithAlias Inline Inherit 4 True) input
   where
     expected = unlines
         [ "module Herp where"
@@ -207,7 +208,7 @@ case08 = expected
 --------------------------------------------------------------------------------
 case09 :: Assertion
 case09 = expected
-    @=? testStep (step 80 $ Align Global WithAlias Multiline 4 True) input
+    @=? testStep (step 80 $ Align Global WithAlias Multiline Inherit 4 True) input
   where
     expected = unlines
         [ "module Herp where"
@@ -241,7 +242,7 @@ case09 = expected
 --------------------------------------------------------------------------------
 case10 :: Assertion
 case10 = expected
-    @=? testStep (step 40 $ Align Group WithAlias Multiline 4 True) input
+    @=? testStep (step 40 $ Align Group WithAlias Multiline Inherit 4 True) input
   where
     expected = unlines
         [ "module Herp where"
@@ -280,7 +281,7 @@ case10 = expected
 --------------------------------------------------------------------------------
 case11 :: Assertion
 case11 = expected
-    @=? testStep (step 80 $ Align Group NewLine Inline 4 True) input
+    @=? testStep (step 80 $ Align Group NewLine Inline Inherit 4 True) input
   where
     expected = unlines
         [ "module Herp where"
@@ -308,7 +309,7 @@ case11 = expected
 --------------------------------------------------------------------------------
 case12 :: Assertion
 case12 = expected
-    @=? testStep (step 80 $ Align Group NewLine Inline 2 True) input'
+    @=? testStep (step 80 $ Align Group NewLine Inline Inherit 2 True) input'
   where
     input' = unlines
         [ "import Data.List (map)"
@@ -323,7 +324,7 @@ case12 = expected
 --------------------------------------------------------------------------------
 case13 :: Assertion
 case13 = expected
-    @=? testStep (step 80 $ Align None WithAlias InlineWithBreak 4 True) input'
+    @=? testStep (step 80 $ Align None WithAlias InlineWithBreak Inherit 4 True) input'
   where
     input' = unlines
         [ "import qualified Data.List as List (concat, foldl, foldr, head, init,"
@@ -341,7 +342,7 @@ case13 = expected
 case14 :: Assertion
 case14 = expected
     @=? testStep
-      (step 80 $ Align None WithAlias InlineWithBreak 10 True) expected
+      (step 80 $ Align None WithAlias InlineWithBreak Inherit 10 True) expected
   where
     expected = unlines
         [ "import qualified Data.List as List (concat, map, null, reverse, tail, (++))"
@@ -351,7 +352,7 @@ case14 = expected
 --------------------------------------------------------------------------------
 case15 :: Assertion
 case15 = expected
-    @=? testStep (step 80 $ Align None AfterAlias Multiline 4 True) input'
+    @=? testStep (step 80 $ Align None AfterAlias Multiline Inherit 4 True) input'
   where
     expected = unlines
         [ "import Data.Acid (AcidState)"
@@ -377,7 +378,7 @@ case15 = expected
 --------------------------------------------------------------------------------
 case16 :: Assertion
 case16 = expected
-    @=? testStep (step 80 $ Align None AfterAlias Multiline 4 False) input'
+    @=? testStep (step 80 $ Align None AfterAlias Multiline Inherit 4 False) input'
   where
     expected = unlines
         [ "import Data.Acid (AcidState)"
@@ -401,7 +402,7 @@ case16 = expected
 --------------------------------------------------------------------------------
 case17 :: Assertion
 case17 = expected
-    @=? testStep (step 80 $ Align None AfterAlias Multiline 4 True) input'
+    @=? testStep (step 80 $ Align None AfterAlias Multiline Inherit 4 True) input'
   where
     expected = unlines
         [ "import Control.Applicative (Applicative (pure, (<*>)))"
@@ -419,7 +420,7 @@ case17 = expected
 --------------------------------------------------------------------------------
 case18 :: Assertion
 case18 = expected @=? testStep
-    (step 40 $ Align None AfterAlias InlineToMultiline 4 True) input'
+    (step 40 $ Align None AfterAlias InlineToMultiline Inherit 4 True) input'
   where
     expected = unlines
            ----------------------------------------
@@ -442,3 +443,26 @@ case18 = expected @=? testStep
         , ""
         , "import Data.Acid as Acid (closeAcidState, createCheckpoint, openLocalStateFrom)"
         ]
+
+--------------------------------------------------------------------------------
+case19 :: Assertion
+case19 = expected @=? testStep
+    (step 40 $ Align Global NewLine InlineWithBreak RightAfter 17 True) input'
+  where
+    expected = unlines
+           ----------------------------------------
+        [ "import           Prelude ()"
+        , "import           Prelude.Compat hiding"
+        , "                 (foldMap)"
+        , ""
+        , "import           Data.List"
+        , "                 (foldl', intercalate,"
+        , "                 intersperse)"
+        ]
+
+    input' = unlines
+        [ "import Prelude.Compat hiding (foldMap)"
+        , "import Prelude ()"
+        , ""
+        , "import Data.List (foldl', intercalate, intersperse)"
+        ]