Use ghc-lib-parser rather than haskell-src-exts

This patch swaps out the parsing library from `haskell-src-exts` to
`ghc-lib-parser`, which gives us better compatibility with GHC.

Because almost every module heavily used the Haskell AST provided by
`haskell-src-exts`, this was a huge effort and it would not have been possible
without Felix Mulder doing an initial port, GSoC student Beatrice Vergani
porting several other steps, and Łukasz Gołębiewski and Paweł Szulc who helped
me finish up things in the home stretch.

I've generally tried to keep styling 100% compatible with what was there before,
but some issues may have unintentionally slipped in so please report those.

This introduces one new import styling contributed by Felix: when wrapping
import lists over multiple lines, you can repeat the module name, e.g.:

    import Control.Monad.Except as X (ExceptT (..), MonadError (..), liftEither)
    import Control.Monad.Except as X (runExceptT, withExceptT)

This is activated by using `import_align: repeat`.

Secondly, a new Step was added, `module_header`, which formats the export list
of a module, including the trailing `where` clause.  Details for this new step
can be found in the `data/stylish-haskell.yaml`.

Co-Authored-By: Beatrice Vergani <beatrice.vergani11@gmail.com>
Co-Authored-By: Paweł Szulc <paul.szulc@gmail.com>
Co-Authored-By: Łukasz Gołębiewski <lukasz.golebiewski@gmail.com>
Co-Authored-By: Felix Mulder <felix.mulder@klarna.com>

1 files changed, 9 insertions, 21 deletions

diff --git a/lib/Language/Haskell/Stylish/Block.hs b/lib/Language/Haskell/Stylish/Block.hs
index 46111ee..9b07420 100644
--- a/lib/Language/Haskell/Stylish/Block.hs
+++ b/lib/Language/Haskell/Stylish/Block.hs
@@ -4,20 +4,17 @@ module Language.Haskell.Stylish.Block
     , LineBlock
     , SpanBlock
     , blockLength
-    , linesFromSrcSpan
-    , spanFromSrcSpan
     , moveBlock
     , adjacent
     , merge
+    , mergeAdjacent
     , overlapping
     , groupAdjacent
     ) where
 
 
 --------------------------------------------------------------------------------
-import           Control.Arrow         (arr, (&&&), (>>>))
-import qualified Data.IntSet           as IS
-import qualified Language.Haskell.Exts as H
+import qualified Data.IntSet as IS
 
 
 --------------------------------------------------------------------------------
@@ -25,7 +22,8 @@ import qualified Language.Haskell.Exts as H
 data Block a = Block
     { blockStart :: Int
     , blockEnd   :: Int
-    } deriving (Eq, Ord, Show)
+    }
+    deriving (Eq, Ord, Show)
 
 
 --------------------------------------------------------------------------------
@@ -40,21 +38,6 @@ type SpanBlock = Block Char
 blockLength :: Block a -> Int
 blockLength (Block start end) = end - start + 1
 
-
---------------------------------------------------------------------------------
-linesFromSrcSpan :: H.SrcSpanInfo -> LineBlock
-linesFromSrcSpan = H.srcInfoSpan >>>
-    H.srcSpanStartLine &&& H.srcSpanEndLine >>>
-    arr (uncurry Block)
-
-
---------------------------------------------------------------------------------
-spanFromSrcSpan :: H.SrcSpanInfo -> SpanBlock
-spanFromSrcSpan = H.srcInfoSpan >>>
-    H.srcSpanStartColumn &&& H.srcSpanEndColumn >>>
-    arr (uncurry Block)
-
-
 --------------------------------------------------------------------------------
 moveBlock :: Int -> Block a -> Block a
 moveBlock offset (Block start end) = Block (start + offset) (end + offset)
@@ -94,3 +77,8 @@ groupAdjacent = foldr go []
     go (b1, x) gs = case break (adjacent b1 . fst) gs of
         (_, [])               -> (b1, [x]) : gs
         (ys, ((b2, xs) : zs)) -> (merge b1 b2, x : xs) : (ys ++ zs)
+
+mergeAdjacent :: [Block a] -> [Block a]
+mergeAdjacent (a : b : rest) | a `adjacent` b = merge a b : mergeAdjacent rest
+mergeAdjacent (a : rest)     = a : mergeAdjacent rest
+mergeAdjacent []             = []