Add instance formatting for simple case

src-literatetests/10-tests.blt

@@ -905,3 +905,111 @@ import qualified Data.List                               as L
 
 -- Test
 import           Test                                     ( test )
+
+###############################################################################
+###############################################################################
+###############################################################################
+#group class.instance
+###############################################################################
+###############################################################################
+###############################################################################
+
+#test simple-instance
+
+instance MyClass Int where
+  myMethod x = x + 1
+
+#test simple-method-signature
+
+instance MyClass Int where
+  myMethod :: Int -> Int
+  myMethod x = x + 1
+
+#test simple-long-method-signature
+
+instance MyClass Int where
+  myMethod
+    :: Int
+    -> Int
+    -> AReallyLongType
+    -> AReallyLongType
+    -> AReallyLongType
+    -> Int
+  myMethod x = x + 1
+
+#test simple-two-methods
+
+instance MyClass Int where
+  myMethod x = x + 1
+  myMethod2 x = x + 1
+
+#test simple-two-signatures
+
+instance MyClass Int where
+  myMethod
+    :: Int
+    -> Int
+    -> AReallyLongType
+    -> AReallyLongType
+    -> AReallyLongType
+    -> Int
+  myMethod x = x + 1
+
+  myMethod2 :: Int -> Int
+  myMethod2 x = x + 1
+
+#test simple-instance-comment
+
+-- | This instance should be commented on
+instance MyClass Int where
+
+  -- | This method is also comment-worthy
+  myMethod x = x + 1
+
+#test instance-with-type-family
+
+instance MyClass Int where
+  type MyType = Int
+
+  myMethod :: MyType -> Int
+  myMethod x = x + 1
+
+#test instance-with-type-family-below-method
+
+instance MyClass Int where
+
+  type MyType = String
+
+  myMethod :: MyType -> Int
+  myMethod x = x + 1
+
+  type MyType = Int
+
+#test instance-with-data-family
+
+instance MyClass Int where
+
+  -- | This data is very important
+  data MyData = IntData
+    { intData  :: String
+    , intData2 :: Int
+    }
+
+  myMethod :: MyData -> Int
+  myMethod = intData2
+
+#test instance-with-data-family-below-method
+
+instance MyClass Int where
+  -- | This data is important
+  data MyData = Test Int Int
+
+  myMethod :: MyData -> Int
+  myMethod = intData2
+
+  -- | This data is also important
+  data MyData2 = IntData
+    { intData  :: String
+    -- ^ Interesting field
+    , intData2 :: Int
+    }

src/Language/Haskell/Brittany/Internal/Layouters/Decl.hs

@@ -27,7 +27,7 @@ import           Language.Haskell.Brittany.Internal.ExactPrintUtils
 import           Language.Haskell.Brittany.Internal.Utils
 
 import           GHC ( runGhc, GenLocated(L), moduleNameString )
-import           SrcLoc ( SrcSpan, noSrcSpan )
+import           SrcLoc ( SrcSpan, noSrcSpan, Located , getLoc, unLoc )
 import           HsSyn
 import           Name
 import           BasicTypes ( InlinePragma(..)
@@ -42,7 +42,7 @@ import {-# SOURCE #-} Language.Haskell.Brittany.Internal.Layouters.Expr
 import {-# SOURCE #-} Language.Haskell.Brittany.Internal.Layouters.Stmt
 import           Language.Haskell.Brittany.Internal.Layouters.Pattern
 
-import           Bag ( mapBagM )
+import           Bag ( mapBagM, bagToList, emptyBag )
 
 
 
@@ -65,16 +65,42 @@ layoutDecl d@(L loc decl) = case decl of
                                (foldedAnnKeys d)
                                False
                                (Text.pack str)
+  InstD (ClsInstD inst) -> withTransformedAnns d $ layoutClsInst (L loc inst)
   _ -> briDocByExactNoComment d
 
 
 layoutSig :: ToBriDoc Sig
 layoutSig lsig@(L _loc sig) = case sig of
 #if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */
-  TypeSig names (HsWC _ (HsIB _ typ _)) -> docWrapNode lsig $ do
+  TypeSig names (HsWC _ (HsIB _ typ _)) -> layoutNamesAndType names typ
 #else /* ghc-8.0 */
-  TypeSig names (HsIB _ (HsWC _ _ typ)) -> docWrapNode lsig $ do
+  TypeSig names (HsIB _ (HsWC _ _ typ)) -> layoutNamesAndType names typ
 #endif
+  InlineSig name (InlinePragma _ spec _arity phaseAct conlike) ->
+    docWrapNode lsig $ do
+      nameStr <- lrdrNameToTextAnn name
+      specStr <- specStringCompat lsig spec
+      let phaseStr = case phaseAct of
+            NeverActive      -> "" -- not [] - for NOINLINE NeverActive is
+                                   -- in fact the default
+            AlwaysActive     -> ""
+            ActiveBefore _ i -> "[~" ++ show i ++ "] "
+            ActiveAfter  _ i -> "[" ++ show i ++ "] "
+      let conlikeStr = case conlike of
+            FunLike -> ""
+            ConLike -> "CONLIKE "
+      docLit
+        $  Text.pack ("{-# " ++ specStr ++ conlikeStr ++ phaseStr)
+        <> nameStr
+        <> Text.pack " #-}"
+#if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */
+  ClassOpSig False names (HsIB _ typ _) -> layoutNamesAndType names typ
+#else /* ghc-8.0 */
+  ClassOpSig False names (HsIB _ typ) -> layoutNamesAndType names typ
+#endif
+  _ -> briDocByExactNoComment lsig -- TODO
+ where
+  layoutNamesAndType names typ = docWrapNode lsig $ do
     nameStrs <- names `forM` lrdrNameToTextAnn
     let nameStr = Text.intercalate (Text.pack ", ") $ nameStrs
     typeDoc     <- docSharedWrapper layoutType typ
@@ -112,24 +138,7 @@ layoutSig lsig@(L _loc sig) = case sig of
                  ]
                )
              ]
-  InlineSig name (InlinePragma _ spec _arity phaseAct conlike) ->
-    docWrapNode lsig $ do
-      nameStr <- lrdrNameToTextAnn name
-      specStr <- specStringCompat lsig spec
-      let phaseStr = case phaseAct of
-            NeverActive      -> "" -- not [] - for NOINLINE NeverActive is
-                                   -- in fact the default
-            AlwaysActive     -> ""
-            ActiveBefore _ i -> "[~" ++ show i ++ "] "
-            ActiveAfter  _ i -> "[" ++ show i ++ "] "
-      let conlikeStr = case conlike of
-            FunLike -> ""
-            ConLike -> "CONLIKE "
-      docLit
-        $  Text.pack ("{-# " ++ specStr ++ conlikeStr ++ phaseStr)
-        <> nameStr
-        <> Text.pack " #-}"
-  _ -> briDocByExactNoComment lsig -- TODO
+
 
 specStringCompat
   :: MonadMultiWriter [BrittanyError] m => LSig GhcPs -> InlineSpec -> m String
@@ -585,3 +594,97 @@ layoutPatternBindFinal alignmentToken binderDoc mPatDoc clauseDocs mWhereDocs ha
                       ]
          ]
       ++ wherePartMultiLine
+
+-- | Layout an @instance@ declaration
+--
+--   Layout signatures and bindings using the corresponding layouters from the
+--   top-level. Layout the instance head, type family instances, and data family
+--   instances using ExactPrint.
+layoutClsInst :: ToBriDoc ClsInstDecl
+layoutClsInst lcid@(L _ cid) = docLines
+  [ layoutInstanceHead
+  , docEnsureIndent BrIndentRegular
+  $  docSortedLines
+  $  fmap layoutAndLocateSig          (cid_sigs cid)
+  ++ fmap layoutAndLocateBind         (bagToList $ cid_binds cid)
+  ++ fmap layoutAndLocateTyFamInsts   (cid_tyfam_insts cid)
+  ++ fmap layoutAndLocateDataFamInsts (cid_datafam_insts cid)
+  ]
+ where
+  layoutInstanceHead :: ToBriDocM BriDocNumbered
+  layoutInstanceHead =
+    briDocByExactNoComment $ InstD . ClsInstD . removeChildren <$> lcid
+
+  removeChildren :: ClsInstDecl p -> ClsInstDecl p
+  removeChildren c = c
+    { cid_binds         = emptyBag
+    , cid_sigs          = []
+    , cid_tyfam_insts   = []
+    , cid_datafam_insts = []
+    }
+
+  -- | Like 'docLines', but sorts the lines based on location
+  docSortedLines
+    :: [ToBriDocM (Located BriDocNumbered)] -> ToBriDocM BriDocNumbered
+  docSortedLines l =
+    allocateNode . BDFLines . fmap unLoc . List.sortOn getLoc =<< sequence l
+
+  layoutAndLocateSig :: ToBriDocC (Sig GhcPs) (Located BriDocNumbered)
+  layoutAndLocateSig lsig@(L loc _) = L loc <$> layoutSig lsig
+
+  layoutAndLocateBind :: ToBriDocC (HsBind GhcPs) (Located BriDocNumbered)
+  layoutAndLocateBind lbind@(L loc _) =
+    L loc <$> (joinBinds =<< layoutBind lbind)
+
+  joinBinds
+    :: Either [BriDocNumbered] BriDocNumbered -> ToBriDocM BriDocNumbered
+  joinBinds = \case
+    Left  ns -> docLines $ return <$> ns
+    Right n  -> return n
+
+  layoutAndLocateTyFamInsts
+    :: ToBriDocC (TyFamInstDecl GhcPs) (Located BriDocNumbered)
+  layoutAndLocateTyFamInsts ltfid@(L loc _) =
+    L loc <$> layoutTyFamInstDecl ltfid
+
+  -- | Send to ExactPrint then remove unecessary whitespace
+  layoutTyFamInstDecl :: ToBriDoc TyFamInstDecl
+  layoutTyFamInstDecl ltfid =
+    fmap stripWhitespace <$> briDocByExactNoComment ltfid
+
+  layoutAndLocateDataFamInsts
+    :: ToBriDocC (DataFamInstDecl GhcPs) (Located BriDocNumbered)
+  layoutAndLocateDataFamInsts ldfid@(L loc _) =
+    L loc <$> layoutDataFamInstDecl ldfid
+
+  -- | Send to ExactPrint then remove unecessary whitespace
+  layoutDataFamInstDecl :: ToBriDoc DataFamInstDecl
+  layoutDataFamInstDecl ldfid =
+    fmap stripWhitespace <$> briDocByExactNoComment ldfid
+
+  -- | ExactPrint adds indentation/newlines to @data@/@type@ declarations
+  stripWhitespace :: BriDocF f -> BriDocF f
+  stripWhitespace (BDFExternal ann anns b t) =
+    BDFExternal ann anns b $ stripWhitespace' t
+  stripWhitespace b = b
+
+  -- | We strip the first newline from each @data@/@type@ declaration. If the
+  --   @data@/@type@ is the first declaration in the instance, then we also have
+  --   to strip whitespace from the start of the comments and the first line of
+  --   the declaration. This is brittle and should be replaced by proper
+  --   layouting
+  --   as soon as possible.
+  stripWhitespace' :: Text -> Text
+  stripWhitespace' t =
+    let
+      isTypeOrData t' =
+        Text.pack "type"
+          `Text.isPrefixOf` t'
+          ||                Text.pack "data"
+          `Text.isPrefixOf` t'
+      (comments, dat : rest) =
+        break (isTypeOrData . Text.stripStart) (Text.lines (Text.tail t))
+    in Text.init
+      $  Text.unlines
+      $  fmap Text.stripStart comments
+      ++ (Text.stripStart dat : rest)

stack-8.4.3.yaml

@@ -0,0 +1,4 @@
+resolver: lts-12.12
+
+extra-deps:
+  - ghc-exactprint-0.5.8.1