Fix for exception on hanging doublequote

src/Data/Csv/Parser.hs

@@ -154,17 +154,20 @@ field !delim = do
 escapedField :: AL.Parser S.ByteString
 escapedField = do
     _ <- dquote
-    -- The scan state is 'True' if the previous character was a double
-    -- quote.  We need to drop a trailing double quote left by scan.
-    s <- S.init <$> (A.scan False $ \s c -> if c == doubleQuote
-                                            then Just (not s)
-                                            else if s then Nothing
-                                                 else Just False)
-    if doubleQuote `S.elem` s
-        then case Z.parse unescape s of
-            Right r  -> return r
-            Left err -> fail err
-        else return s
+    -- The scan state is 'True' if the previous character was a double quote.
+    s' <- A.scan False $ \s c -> if c == doubleQuote
+                                 then Just (not s)
+                                 else if s then Nothing
+                                      else Just False
+    -- We need to drop a trailing double quote left by scan.
+    if S.null s'
+      then fail "trailing double quote"
+      else let s = S.init s'
+           in if doubleQuote `S.elem` s
+              then case Z.parse unescape s of
+                     Right r  -> return r
+                     Left err -> fail err
+              else return s
 
 unescapedField :: Word8 -> AL.Parser S.ByteString
 unescapedField !delim = A.takeWhile (\ c -> c /= doubleQuote &&

tests/UnitTests.hs

@@ -21,6 +21,7 @@ import qualified Data.Text as T
 import qualified Data.Text.Lazy as LT
 import qualified Data.Vector as V
 import qualified Data.Foldable as F
+import Data.List (isPrefixOf)
 import Data.Word
 import Numeric.Natural
 import GHC.Generics (Generic)
@@ -56,6 +57,14 @@ assertResult input expected res = case res of
                 "      input: " ++ show (BL8.unpack input) ++ "\n" ++
                 "parse error: " ++ err
 
+decodeFailsWith :: BL.ByteString -> String -> Assertion
+decodeFailsWith input expected = case decode NoHeader input of
+    Right r  -> assertFailure $ "input: " ++ show (BL8.unpack input) ++ "\n" ++
+                "retuned: " ++ show (r :: (V.Vector (V.Vector B.ByteString))) ++ "\n" ++
+                "whereas should have failed with " <> expected
+    Left err -> assertBool ("got " <> err <> "\ninstead of " <> expected)
+                $ ("parse error ("++expected++")") `isPrefixOf` err
+
 encodesAs :: [[B.ByteString]] -> BL.ByteString -> Assertion
 encodesAs input expected =
     encode (map V.fromList input) @?= expected
@@ -166,6 +175,7 @@ positionalTests =
       [ testGroup "decode" $ map streamingDecodeTest decodeTests
       , testGroup "decodeWith" $ map streamingDecodeWithTest decodeWithTests
       ]
+    , testGroup "escaped" escapedTests
     ]
   where
     rfc4180Input = BL8.pack $
@@ -210,6 +220,15 @@ positionalTests =
     defEncAllEnq  = defaultEncodeOptions { encQuoting = QuoteAll  }
     defDec = defaultDecodeOptions
 
+    escapedTests = [
+      testCase "escaped" $
+        "\"x,y\",z\nbaz,\"bar\nfoo,\"" `decodesAs` [["x,y", "z"], ["baz", "bar\nfoo,"]],
+      testCase "escapedMalformed1" $
+        "\"x,\"y" `decodeFailsWith` "Failed reading: satisfy",
+      testCase "escapedMalformed0" $
+        "baz,\"" `decodeFailsWith` "Failed reading: trailing double quote"
+      ]
+
 nameBasedTests :: [TF.Test]
 nameBasedTests =
     [ testGroup "encode" $ map encodeTest