Record alignment takes max columns into account

3 files changed, 32 insertions, 9 deletions

diff --git a/lib/Language/Haskell/Stylish.hs b/lib/Language/Haskell/Stylish.hs
index 103306c..cfc7807 100644
--- a/lib/Language/Haskell/Stylish.hs
+++ b/lib/Language/Haskell/Stylish.hs
@@ -59,7 +59,8 @@ languagePragmas = LanguagePragmas.step
 
 
 --------------------------------------------------------------------------------
-records :: Step
+records :: Int   -- ^ columns
+        -> Step
 records = Records.step
 
 
diff --git a/lib/Language/Haskell/Stylish/Config.hs b/lib/Language/Haskell/Stylish/Config.hs
index fee7594..2f72958 100644
--- a/lib/Language/Haskell/Stylish/Config.hs
+++ b/lib/Language/Haskell/Stylish/Config.hs
@@ -205,7 +205,7 @@ parseLanguagePragmas config o = LanguagePragmas.step
 
 --------------------------------------------------------------------------------
 parseRecords :: Config -> A.Object -> A.Parser Step
-parseRecords _ _ = return Records.step
+parseRecords c _ = return (Records.step $ configColumns c)
 
 
 --------------------------------------------------------------------------------
diff --git a/lib/Language/Haskell/Stylish/Step/Records.hs b/lib/Language/Haskell/Stylish/Step/Records.hs
index c8f6d19..1c46024 100644
--- a/lib/Language/Haskell/Stylish/Step/Records.hs
+++ b/lib/Language/Haskell/Stylish/Step/Records.hs
@@ -31,6 +31,10 @@ data Alignable a = Alignable
     { aContainer :: !a
     , aLeft      :: !a
     , aRight     :: !a
+    -- | This is the minimal number of columns we need for the leading part not
+    -- included in our right string.  For example, for datatype alignment, this
+    -- leading part is the string ":: " so we use 3.
+    , aRightLead :: !Int
     } deriving (Show)
 
 
@@ -40,20 +44,38 @@ fieldDeclToAlignable (H.FieldDecl ann names ty) = Alignable
     { aContainer = ann
     , aLeft      = H.ann (last names)
     , aRight     = H.ann ty
+    , aRightLead = length ":: "
     }
 
 
 --------------------------------------------------------------------------------
 -- | Align the type of a field
-align :: [Alignable H.SrcSpan] -> [Change String]
-align alignment = map align' alignment
+align :: Int -> [Alignable H.SrcSpan] -> [Change String]
+align maxColumns alignment
+    -- Do not make any change if we would go past the maximum number of columns.
+    | longestLeft + longestRight > maxColumns = info []
+    | otherwise                               = info $ map align' alignment
   where
-    longest = maximum $ map (H.srcSpanEndColumn . aLeft) alignment
+    info =
+        id
+        -- trace ("Alignable: " ++ show alignment) .
+        -- trace ("longestLeft: " ++ show longestLeft) .
+        -- trace ("longestRight: " ++ show longestRight)
+
+    -- The longest thing in the left column.
+    longestLeft = maximum $ map (H.srcSpanEndColumn . aLeft) alignment
+
+    -- The longest thing in the right column.
+    longestRight = maximum
+        [ H.srcSpanEndColumn (aRight a) - H.srcSpanStartColumn (aRight a)
+            + aRightLead a
+        | a <- alignment
+        ]
 
     align' a = changeLine (H.srcSpanStartLine $ aContainer a) $ \str ->
         let column      = H.srcSpanEndColumn $ aLeft a
             (pre, post) = splitAt column str
-        in [padRight longest (trimRight pre) ++ trimLeft post]
+        in [padRight longestLeft (trimRight pre) ++ trimLeft post]
 
     trimLeft  = dropWhile isSpace
     trimRight = reverse . trimLeft . reverse
@@ -72,8 +94,8 @@ fixable fields = all singleLine containers && nonOverlapping containers
 
 
 --------------------------------------------------------------------------------
-step :: Step
-step = makeStep "Records" $ \ls (module', _) ->
+step :: Int -> Step
+step maxColumns = makeStep "Records" $ \ls (module', _) ->
     let module''       = fmap H.srcInfoSpan module'
         fixableRecords = filter fixable $ records module''
-    in applyChanges (fixableRecords >>= align) ls
+    in applyChanges (fixableRecords >>= align maxColumns) ls