Requirements.txt: fix hang when parsing unsupported fields

Changelog.md

@@ -1,3 +1,7 @@
+# Unreleased
+
+- Requirements.txt: fix hang when parsing unsupported fields ([#235](https://github.com/fossas/spectrometer/pull/235))
+
 # v2.5.14
 
 - Golang: map package imports to modules ([#234](https://github.com/fossas/spectrometer/pull/234))

src/Strategy/Python/ReqTxt.hs

@@ -34,22 +34,18 @@ reqParser = [] <$ char '-' <* ignored -- pip options
      <|> [] <$ char '/' <* ignored -- absolute path
      <|> [] <$ oneOfS ["http:", "https:", "git+", "hg+", "svn+", "bzr+"] <* ignored -- URLs
      <|> [] <$ comment
-     <|> (pure <$> requirementParser <* ignored)
-     <|> pure [] -- empty line
+     <|> (pure <$> try requirementParser <* ignored)
+     <|> [] <$ ignored -- something else we're not able to parse
 
   where
   isEndLine :: Char -> Bool
   isEndLine '\n' = True
   isEndLine '\r' = True
-  isEndLine '\\' = True
   isEndLine _    = False
 
   -- ignore content until the end of the line
   ignored :: Parser ()
-  ignored = () <$ takeWhileP (Just "ignored") (not . isEndLine) <* (try newLine <|> (() <$ takeWhileP (Just "end of line") isEndLine))
-
-  newLine :: Parser ()
-  newLine = char '\\' <* takeWhileP (Just "endLine") isEndLine *> ignored
+  ignored = () <$ takeWhileP (Just "ignored") (not . isEndLine) <* takeWhileP (Just "end of line") isEndLine
 
   comment :: Parser ()
   comment = char '#' *> ignored

test/Python/RequirementsSpec.hs

@@ -82,7 +82,7 @@ spec = do
     T.it "can parse" $
       case runParser requirementsTxtParser "" requirementsTextFile of
         Left r -> do
-          T.expectationFailure $ "failed to parse: error:" ++ show r
+          T.expectationFailure $ "failed to parse: error:" ++ errorBundlePretty r
         Right res -> do
           let result = buildGraph res
           expectDeps [depOne, depTwo, depThree, depFour] result

test/Python/testdata/req.txt

@@ -4,4 +4,5 @@ three==3.0.0 \
   --hash=sha256:30639c035cdb23534cd4aa2dd52c3bf48f06e5f4a941509c8bafd8ce11080259 \
   --hash=sha256:8b74bedcbbbaca38ff6d7491d76f2b06b3592611af620f8426e82dddb04a5ced \
   # via python-dateuti
-four==4.0.0 #help
+[foo]
+four==4.0.0 #help