InvalidQuery raised for invalid tag query while rendering wiki text

[Jun Omae]

Originally reported at ​https://trac.ffmpeg.org/ticket/11386.

Internal Server Error occurs or page rendering stops due to InvalidQuery while rendering wiki within invalid tag query like tag:s:s.

This plugin should ignore such an invalid tag query or render an error message like the behavior for invalid ticket query:

• Rendering for query:foo&bar: [Error: Query filter requires field and constraints separated by a "="]

  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1625, in format_to_html
    return HtmlFormatter(env, context, wikidom).generate(escape_newlines)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1580, in generate
    escape_newlines)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1362, in format
    result = re.sub(self.wikiparser.rules, self.replace, line)
  File "/srv/trac-hacks.org/pve/lib/python2.7/re.py", line 155, in sub
    return _compile(pattern, flags).sub(repl, string, count)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1277, in replace
    replacement = self.handle_match(fullmatch)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1273, in handle_match
    return internal_handler(match, fullmatch)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 639, in _shref_formatter
    return self._make_link(ns, target, match, match, fullmatch)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/trac/wiki/formatter.py", line 690, in _make_link
    fullmatch)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/tractags/wiki.py", line 359, in _format_tagged
    query))):
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/tractags/wiki.py", line 373, in iter_is_empty
    i.next()
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/tractags/api.py", line 391, in query
    query = Query(query, attribute_handlers=all_attribute_handlers)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/tractags/query.py", line 171, in __init__
    root = self.parse(tokens)
  File "/srv/trac-hacks.org/pve/local/lib/python2.7/site-packages/tractags/query.py", line 193, in parse
    raise InvalidQuery(_("Attribute must be a word"))
InvalidQuery: Attribute must be a word