Print line violations only under --verbose flag

Alleviates agda#48 but a proper performance fix would be better.

FixWhitespace.hs

@@ -21,7 +21,7 @@ import           System.IO                    ( IOMode(WriteMode), hPutStr, hPut
 import           Text.Read                    ( readMaybe )
 
 import           Data.Text.FixWhitespace      ( CheckResult(CheckOK, CheckViolation, CheckIOError), checkFile, displayLineError
-                                              , TabSize, defaultTabSize )
+                                              , TabSize, Verbose, defaultTabSize )
 
 import           ParseConfig                  ( Config(Config), parseConfig )
 import qualified Paths_fix_whitespace         as PFW ( version )
@@ -37,8 +37,6 @@ data Mode
   | Check  -- ^ Check if there are any whitespace issues.
     deriving (Show, Eq)
 
-type Verbose = Bool
-
 data Options = Options
   { optVerbose :: Verbose
   -- ^ Display the location of a file being checked or not.
@@ -203,28 +201,33 @@ main = do
 
 fix :: Mode -> Verbose -> TabSize -> FilePath -> IO Bool
 fix mode verbose tabSize f =
-  checkFile tabSize f >>= \case
+  checkFile tabSize verbose f >>= \case
 
     CheckOK -> do
       when verbose $
         putStrLn $ "[ Checked ] " ++ f
       return False
 
-    CheckViolation s vs -> do
-      hPutStrLn stderr $
-        "[ Violation " ++
-        (if mode == Fix then "fixed" else "detected") ++
-        " ] " ++ f ++
-        (if mode == Fix then "" else
-           ":\n" ++ (unlines $ map (Text.unpack . displayLineError f) vs))
-
+    CheckViolation s vs ->  do
+      hPutStrLn stderr (msg vs)
       when (mode == Fix) $
         withFile f WriteMode $ \h -> do
           hSetEncoding h utf8
           Text.hPutStr h s
       return True
 
+
     CheckIOError _e -> do
       hPutStrLn stderr $
         "[ Read error ] " ++ f
       return False
+
+  where
+    msg vs
+      | mode == Fix =
+        "[ Violation fixed ] " ++ f
+
+      | otherwise =
+        "[ Violation detected ] " ++ f ++
+        (if not verbose then "" else
+           ":\n" ++ unlines (map (Text.unpack . displayLineError f) vs))

src/Data/Text/FixWhitespace.hs

@@ -7,7 +7,9 @@ module Data.Text.FixWhitespace
   , LineError(..)
   , displayLineError
   , transform
+  , transformWithLog
   , TabSize
+  , Verbose
   , defaultTabSize
   )
   where
@@ -23,12 +25,13 @@ import qualified Data.Text.IO                      as Text  {- Strict IO -}
 
 import           System.IO                         ( IOMode(ReadMode), hSetEncoding, utf8, withFile )
 
-import           Data.List.Extra.Drop              ( dropWhileEnd1 )
+import           Data.List.Extra.Drop              ( dropWhileEnd1, dropWhile1 )
 
+type Verbose = Bool
 type TabSize = Int
 
 -- | Default tab size.
-
+--
 defaultTabSize :: TabSize
 defaultTabSize = 8
 
@@ -51,27 +54,42 @@ data LineError = LineError Int Text
 -- | Check a file against the whitespace policy,
 --   returning a fix if violations occurred.
 --
-checkFile :: TabSize -> FilePath -> IO CheckResult
-checkFile tabSize f =
+checkFile :: TabSize -> Verbose -> FilePath -> IO CheckResult
+checkFile tabSize verbose f =
   handle (\ (e :: IOException) -> return $ CheckIOError e) $
     withFile f ReadMode $ \ h -> do
       hSetEncoding h utf8
       s <- Text.hGetContents h
-      let (s', lvs) = transform tabSize s
+      let (s', lvs)
+            | verbose   = transformWithLog tabSize s
+            | otherwise = (transform tabSize s, [])
       return $ if s' == s then CheckOK else CheckViolation s' lvs
 
+transform
+  :: TabSize   -- ^ Expand tab characters to so many spaces.  Keep tabs if @<= 0@.
+  -> Text      -- ^ Text before transformation.
+  -> Text      -- ^ Text after transformation.
+transform tabSize =
+  Text.unlines .
+  removeFinalEmptyLinesExceptOne .
+  map (removeTrailingWhitespace .  convertTabs tabSize) .
+  Text.lines
+  where
+  removeFinalEmptyLinesExceptOne =
+    reverse . dropWhile1 Text.null . reverse
+
 -- | The transformation monad: maintains info about lines that
---   violate the rules.
+--   violate the rules. Used in the verbose mode to build a log.
 --
 type TransformM = Writer [LineError]
 
 -- | Transforms the contents of a file.
 --
-transform
+transformWithLog
   :: TabSize             -- ^ Expand tab characters to so many spaces.  Keep tabs if @<= 0@.
   -> Text                -- ^ Text before transformation.
   -> (Text, [LineError]) -- ^ Text after transformation and violating lines if any.
-transform tabSize =
+transformWithLog tabSize =
   runWriter .
   fmap Text.unlines .
   fixAllViolations .
@@ -82,7 +100,7 @@ transform tabSize =
   fixAllViolations =
     removeFinalEmptyLinesExceptOne
     <=<
-    mapM (fixLineWith $ removeTrailingWhitespace . convertTabs)
+    mapM (fixLineWith $ removeTrailingWhitespace . convertTabs tabSize)
 
   removeFinalEmptyLinesExceptOne :: [Text] -> TransformM [Text]
   removeFinalEmptyLinesExceptOne ls
@@ -96,9 +114,6 @@ transform tabSize =
     lenLs' = length ls'
     els    = replicate (lenLs - lenLs') ""
 
-  removeTrailingWhitespace =
-    Text.dropWhileEnd $ \ c -> generalCategory c `elem` [Space,Format] || c == '\t'
-
   fixLineWith :: (Text -> Text) -> (Int, Text) -> TransformM Text
   fixLineWith fixer (i, l)
     | l == l'   = pure l
@@ -108,16 +123,22 @@ transform tabSize =
     where
     l' = fixer l
 
-  convertTabs = if tabSize <= 0 then id else
-    Text.pack . reverse . fst . foldl convertOne ([], 0) . Text.unpack
+removeTrailingWhitespace :: Text -> Text
+removeTrailingWhitespace =
+  Text.dropWhileEnd $ \ c -> generalCategory c `elem` [Space,Format] || c == '\t'
 
-  convertOne (a, p) '\t' = (addSpaces n a, p + n)
-    where
-    n = tabSize - p `mod` tabSize  -- Here, tabSize > 0 is guaranteed
-  convertOne (a, p) c = (c:a, p+1)
+convertTabs :: TabSize -> Text -> Text
+convertTabs tabSize = if tabSize <= 0 then id else
+  Text.pack . reverse . fst . foldl (convertOne tabSize) ([], 0) . Text.unpack
+
+convertOne :: TabSize -> (String, Int) -> Char -> (String, Int)
+convertOne tabSize (a, p) '\t' = (addSpaces n a, p + n)
+  where
+  n = tabSize - p `mod` tabSize  -- Here, tabSize > 0 is guaranteed
+convertOne _tabSize (a, p) c = (c:a, p+1)
 
-  addSpaces :: Int -> String -> String
-  addSpaces n = (replicate n ' ' ++)
+addSpaces :: Int -> String -> String
+addSpaces n = (replicate n ' ' ++)
 
 -- | Print a erroneous line with 'visibleSpaces'.
 --

test/Golden.hs

@@ -34,7 +34,7 @@ goldenTests = do
 
 goldenValue :: FilePath -> IO ByteString
 goldenValue file = do
-  checkFile defaultTabSize file >>= \case
+  checkFile defaultTabSize {-verbose: -}True file >>= \case
 
     CheckIOError e ->
       ioError e