Fix applying multiple fixes per line

Fixes #1421

src/ShellCheck/Fixer.hs

@@ -14,18 +14,9 @@ applyFix fix fileLines =
         -- prereq: list is already sorted by start position
         removeOverlap [] = []
         removeOverlap (x:xs) = checkoverlap x xs
-        checkoverlap :: Replacement -> [Replacement] -> [Replacement]
         checkoverlap x [] = x:[]
         checkoverlap x (y:ys) =
             if overlap x y then x:(removeOverlap ys) else x:y:(removeOverlap ys)
-        -- two position overlaps when
-        overlap x y =
-            (yStart >= xStart && yStart < xEnd) || (yStart < xStart && yEnd > xStart)
-            where
-                yStart = repStartPos y
-                yEnd = repEndPos y
-                xStart = repStartPos x
-                xEnd = repEndPos x
 
 
 -- A replacement that spans multiple line is applied by:

src/ShellCheck/Formatter/TTY.hs

@@ -24,6 +24,7 @@ import ShellCheck.Interface
 import ShellCheck.Formatter.Format
 
 import Control.Monad
+import Data.Foldable
 import Data.Ord
 import Data.IORef
 import Data.List
@@ -147,17 +148,19 @@ showFixedString color comments lineNum fileLines =
     let line = fileLines !! fromIntegral (lineNum - 1) in
     -- need to check overlaps
     case filter (hasApplicableFix lineNum) comments of
-        (first:_) -> do
+        [] -> return ()
+        -- all the fixes are single-line only, but there could be multiple
+        -- fixes for that single line. We can fold the fixes (which removes
+        -- overlaps), and apply it as a single fix with multiple replacements.
+        applicableComments -> do
+            let mergedFix = (fold . catMaybes . (map pcFix)) applicableComments
             -- in the spirit of error prone
             putStrLn $ color "message" "Did you mean: "
-            putStrLn $ unlines $ fixedString first fileLines
+            putStrLn $ unlines $ fixedString mergedFix fileLines
-        _ -> return ()
 
-fixedString :: PositionedComment -> [String] -> [String]
+fixedString :: Fix -> [String] -> [String]
-fixedString comment fileLines =
+fixedString fix fileLines =
-    case (pcFix comment) of
+    case (fixReplacements fix) of
-    Nothing -> [""]
-    Just fix -> case (fixReplacements fix) of
         [] -> []
         reps ->
             -- applyReplacement returns the full update file, we really only care about the changed lines

src/ShellCheck/Interface.hs

@@ -54,13 +54,17 @@ module ShellCheck.Interface
     , newFix
     , Replacement(repStartPos, repEndPos, repString)
     , newReplacement
+    , Ranged(overlap)
     ) where
 
 import ShellCheck.AST
 
 import Control.DeepSeq
 import Control.Monad.Identity
+import Data.List
 import Data.Monoid
+import Data.Ord
+import Data.Semigroup
 import GHC.Generics (Generic)
 import qualified Data.Map as Map
 
@@ -270,3 +274,36 @@ mockedSystemInterface files = SystemInterface {
             [] -> return $ Left "File not included in mock."
             [(_, contents)] -> return $ Right contents
 
+-- The Ranged class is used for types that has a start and end position.
+class Ranged a where
+    start   :: a -> Position
+    end     :: a -> Position
+    overlap :: a -> a -> Bool
+    overlap x y =
+        (yStart >= xStart && yStart < xEnd) || (yStart < xStart && yEnd > xStart)
+        where
+            yStart = start y
+            yEnd = end y
+            xStart = start x
+            xEnd = end x
+
+instance Ranged Replacement where
+    start = repStartPos
+    end   = repEndPos
+
+instance Ranged a => Ranged [a] where
+    start [] = newPosition
+    start xs = (minimum . map start) xs
+    end []   = newPosition
+    end xs   = (maximum . map end) xs
+
+instance Ranged Fix where
+    start = start . fixReplacements
+    end   = end . fixReplacements
+
+-- The Monoid instance for Fix merges replacements that do not overlap.
+instance Monoid Fix where
+    mempty = newFix
+    f1 `mappend` f2 = if overlap f1 f2 then f1 else newFix {
+            fixReplacements = fixReplacements f1 ++ fixReplacements f2
+        }