Support for records formatting (#256)

* Initial test describing simplest scenario for Data step

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* [sanity-check] Delete data defs

* Extract changeDecl

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* First green test :-)

* Cover case where there are more then one field in data type declaration

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Add case03 where a type variable is present

* Add case04 - multiple declarations

* Make case04 pass

* Extend tests with case05

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Add pending case06

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Fix case 06

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Add case07

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Add second phantom case

* Add records to config

* Make indent size configurable for records

Co-authored-by: Paweł Szulc <paul.szulc@gmail.com>

* Fix warnings in Data.hs

* Process derivings during record formatting

Co-authored-by: Paweł Szulc <paul.szulc@gmail.com>

* Do not format when context is present

Co-authored-by: Paweł Szulc <paul.szulc@gmail.com>

* Add case 11 - deriving with DerivingStrategies

* Bugfix: do not remove empty data declarations

Co-authored-by: Paweł Szulc <paul.szulc@gmail.com>

* Update README example with ability to format records

* Add case12 (Point)

* Fix case 12

* Factor out processName

* Apply hlint suggestions

* Extract constructors helper function

* Make 'indent' global

* Remove unused Stylish.records method

* Fix Config formatting in Config.hs

* Extract processConstructor function

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Refactor datas function

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Include comments with AST. Two tests are still failing...

* Fix cases 15 and 16

* Do not format records when comments within

Co-authored-by: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>

* Clean-up Data.hs

* Refactor Data.hs

Co-authored-by: Pawel Szulc <paul.szulc@gmail.com>

2 files changed, 75 insertions, 0 deletions

diff --git a/lib/Language/Haskell/Stylish/Config.hs b/lib/Language/Haskell/Stylish/Config.hs
index 725a465..bd15867 100644
--- a/lib/Language/Haskell/Stylish/Config.hs
+++ b/lib/Language/Haskell/Stylish/Config.hs
@@ -35,6 +35,7 @@ import qualified System.IO                                        as IO (Newline
 import qualified Language.Haskell.Stylish.Config.Cabal            as Cabal
 import           Language.Haskell.Stylish.Config.Internal
 import           Language.Haskell.Stylish.Step
+import qualified Language.Haskell.Stylish.Step.Data               as Data
 import qualified Language.Haskell.Stylish.Step.Imports            as Imports
 import qualified Language.Haskell.Stylish.Step.LanguagePragmas    as LanguagePragmas
 import qualified Language.Haskell.Stylish.Step.SimpleAlign        as SimpleAlign
@@ -52,6 +53,7 @@ type Extensions = [String]
 --------------------------------------------------------------------------------
 data Config = Config
     { configSteps              :: [Step]
+    , configIndent             :: Int
     , configColumns            :: Maybe Int
     , configLanguageExtensions :: [String]
     , configNewline            :: IO.Newline
@@ -119,6 +121,7 @@ parseConfig (A.Object o) = do
     -- First load the config without the actual steps
     config <- Config
         <$> pure []
+        <*> (o A..:? "indent"              A..!= 4)
         <*> (o A..:! "columns"             A..!= Just 80)
         <*> (o A..:? "language_extensions" A..!= [])
         <*> (o A..:? "newline"             >>= parseEnum newlines IO.nativeNewline)
@@ -141,6 +144,7 @@ parseConfig _            = mzero
 catalog :: Map String (Config -> A.Object -> A.Parser Step)
 catalog = M.fromList
     [ ("imports",             parseImports)
+    , ("records",             parseRecords)
     , ("language_pragmas",    parseLanguagePragmas)
     , ("simple_align",        parseSimpleAlign)
     , ("squash",              parseSquash)
@@ -180,6 +184,11 @@ parseSimpleAlign c o = SimpleAlign.step
   where
     withDef f k = fromMaybe (f SimpleAlign.defaultConfig) <$> (o A..:? k)
 
+--------------------------------------------------------------------------------
+parseRecords :: Config -> A.Object -> A.Parser Step
+parseRecords c _ = Data.step
+    <$> pure (configIndent c)
+
 
 --------------------------------------------------------------------------------
 parseSquash :: Config -> A.Object -> A.Parser Step
diff --git a/lib/Language/Haskell/Stylish/Step/Data.hs b/lib/Language/Haskell/Stylish/Step/Data.hs
new file mode 100644
index 0000000..9acd22b
--- /dev/null
+++ b/lib/Language/Haskell/Stylish/Step/Data.hs
@@ -0,0 +1,66 @@
+module Language.Haskell.Stylish.Step.Data where
+
+import           Data.List                       (find, intercalate)
+import           Data.Maybe                      (maybeToList)
+import qualified Language.Haskell.Exts           as H
+import           Language.Haskell.Exts.Comments
+import           Language.Haskell.Stylish.Block
+import           Language.Haskell.Stylish.Editor
+import           Language.Haskell.Stylish.Step
+import           Language.Haskell.Stylish.Util
+import           Prelude                         hiding (init)
+
+datas :: H.Module l -> [H.Decl l]
+datas (H.Module _ _ _ _ decls) = decls
+datas _                        = []
+
+type ChangeLine = Change String
+
+step :: Int -> Step
+step indentSize = makeStep "Data" (step' indentSize)
+
+step' :: Int -> Lines -> Module -> Lines
+step' indentSize ls (module', allComments) = applyChanges changes ls
+  where
+    datas' = datas $ fmap linesFromSrcSpan module'
+    changes = datas' >>= maybeToList . changeDecl allComments indentSize
+
+findComment :: LineBlock -> [Comment] -> Maybe Comment
+findComment lb = find commentOnLine
+  where
+    commentOnLine (Comment _ (H.SrcSpan _ start _ end _) _) =
+      blockStart lb == start && blockEnd lb == end
+
+commentsWithin :: LineBlock -> [Comment] -> [Comment]
+commentsWithin lb = filter within
+  where
+    within (Comment _ (H.SrcSpan _ start _ end _) _) =
+      start >= blockStart lb && end <= blockEnd lb
+
+changeDecl :: [Comment] -> Int -> H.Decl LineBlock -> Maybe ChangeLine
+changeDecl _ _ (H.DataDecl _ (H.DataType _) Nothing _ [] _) = Nothing
+changeDecl allComments indentSize (H.DataDecl block (H.DataType _) Nothing dhead decls derivings)
+  | null $ commentsWithin block allComments = Just $ change block (const $ concat newLines)
+  | otherwise = Nothing
+  where
+    newLines = fmap constructors zipped ++ [fmap (indented . H.prettyPrint) derivings]
+    zipped = zip decls ([1..] ::[Int])
+    constructors (decl, 1) = processConstructor allComments typeConstructor indentSize decl
+    constructors (decl, _) = processConstructor allComments (indented "| ") indentSize decl
+    typeConstructor = "data " <> H.prettyPrint dhead <> " = "
+    indented = indent indentSize
+changeDecl _ _ _ = Nothing
+
+processConstructor :: [Comment] -> String -> Int -> H.QualConDecl LineBlock -> [String]
+processConstructor allComments init indentSize (H.QualConDecl _ _ _ (H.RecDecl _ dname fields)) = do
+  init <> H.prettyPrint dname : n1 : ns ++ [indented "}"]
+  where
+    n1 = processName "{ " ( extractField $ head fields)
+    ns = fmap (processName ", " . extractField) (tail fields)
+    processName prefix (fnames, _type, Nothing) =
+      indented prefix <> intercalate ", " (fmap H.prettyPrint fnames) <> " :: " <> H.prettyPrint _type
+    processName prefix (fnames, _type, (Just (Comment _ _ c))) =
+      indented prefix <> intercalate ", " (fmap H.prettyPrint fnames) <> " :: " <> H.prettyPrint _type <> " --" <> c
+    extractField (H.FieldDecl lb names _type) = (names, _type, findComment lb allComments)
+    indented = indent indentSize
+processConstructor _ init _ decl = [init <> trimLeft (H.prettyPrint decl)]