Parsing: many1Till: Check for the end condition before parsing

By not checking for the end condition before the first parse, the
parser was applied too often, consuming too much of the input.

This fixes the behaviour of

  `testStringWith (many1Till (oneOf "ab") (string "aa")) "aaa"`

which before incorrectly returned `Right "a"`. With this change, it
instead correctly fails with `Left (PandocParsecError ...)` because it
is not able to parse at least one occurence of `oneOf "ab"` that is
not `"aa"`.

Note that this only affects `many1Till p end` where `p` matches on a
prefix of `end`.

src/Text/Pandoc/Parsing.hs

@@ -274,11 +274,12 @@ indentWith num = do
                  , try (char '\t' >> indentWith (num - tabStop)) ]
 
 -- | Like @manyTill@, but reads at least one item.
-many1Till :: Stream s m t
+many1Till :: (Show end, Stream s m t)
           => ParserT s st m a
           -> ParserT s st m end
           -> ParserT s st m [a]
 many1Till p end = do
+         notFollowedBy' end
          first <- p
          rest <- manyTill p end
          return (first:rest)
@@ -343,7 +344,7 @@ blanklines :: Stream s m Char => ParserT s st m [Char]
 blanklines = many1 blankline
 
 -- | Parses material enclosed between start and end parsers.
-enclosed :: Stream s  m Char => ParserT s st m t   -- ^ start parser
+enclosed :: (Show end, Stream s  m Char) => ParserT s st m t   -- ^ start parser
          -> ParserT s st m end  -- ^ end parser
          -> ParserT s st m a    -- ^ content parser (to be used repeatedly)
          -> ParserT s st m [a]

src/Text/Pandoc/Readers/Org/Inlines.hs

@@ -687,13 +687,13 @@ mathEnd c = try $ do
   return res
 
 
-enclosedInlines :: PandocMonad m => OrgParser m a
+enclosedInlines :: (PandocMonad m, Show b) => OrgParser m a
                 -> OrgParser m b
                 -> OrgParser m (F Inlines)
 enclosedInlines start end = try $
   trimInlinesF . mconcat <$> enclosed start end inline
 
-enclosedRaw :: PandocMonad m => OrgParser m a
+enclosedRaw :: (PandocMonad m, Show b) => OrgParser m a
             -> OrgParser m b
             -> OrgParser m String
 enclosedRaw start end = try $

src/Text/Pandoc/Readers/TWiki.hs

@@ -349,13 +349,13 @@ linebreak = newline >> notFollowedBy newline >> (lastNewline <|> innerNewline)
   where lastNewline  = eof >> return mempty
         innerNewline = return B.space
 
-between :: (Monoid c, PandocMonad m)
+between :: (Monoid c, PandocMonad m, Show b)
         => TWParser m a -> TWParser m b -> (TWParser m b -> TWParser m c)
         -> TWParser m c
 between start end p =
   mconcat <$> try (start >> notFollowedBy whitespace >> many1Till (p end) end)
 
-enclosed :: (Monoid b, PandocMonad m)
+enclosed :: (Monoid b, PandocMonad m, Show a)
          => TWParser m a -> (TWParser m a -> TWParser m b) -> TWParser m b
 enclosed sep p = between sep (try $ sep <* endMarker) p
   where

src/Text/Pandoc/Readers/Textile.hs

@@ -692,7 +692,7 @@ langAttr = do
   return $ \(id',classes,keyvals) -> (id',classes,("lang",lang):keyvals)
 
 -- | Parses material surrounded by a parser.
-surrounded :: PandocMonad m
+surrounded :: (PandocMonad m, Show t)
            => ParserT [Char] st m t   -- ^ surrounding parser
            -> ParserT [Char] st m a   -- ^ content parser (to be used repeatedly)
            -> ParserT [Char] st m [a]