Hi Anthony,
While investigating a QMP bug reported by a user, I've found a few issues
in our parser/lexer.
The patches in this series fix the problems I was able to solve, but we
still have the following issues:
1. Our 'private extension' is open to the public
Eg. The following input issued by a client is valid:
{ 'execute': 'query-pci' }
I don't think it's a good idea to have clients relying on this kind of
JSON extension.
To fix this we could add a 'extension' flag to JSONLexer and set it to
nonzero in internal functions (eg. qobject_from_jsonf()), of course that
the lexer code should handle this too.
2. QMP doesn't check the return of json_message_parser_feed()
Which means we don't handle JSON syntax errors. While the fix might seem
trivial (ie. just return an error!), I'm not sure what's the best way
to handle this, because the streamer seems to return multiple errors for
the same input string.
For example, this input:
{ "execute": yy_uu }
Seems to return an error for each bad character (yy_uu), shouldn't it
return only once and stop processing the whole string?
3. The lexer enter in ERROR state when processing is done
Not sure whether this is an issue, but I found it while reviewing the code
and maybe this is related with item 2 above.
When json_lexer_feed_char() is finished scanning a string, (ie. ch='\0')
the JSON_SKIP clause will set lexer->state to ERROR as there's no entry
for '\0' in the IN_START array.
Shouldn't we have a LEXER_DONE or something like it instead?
4. Lexer expects a 'terminal' char to process a token
Which means clients must send a sort of end of line char, so that we
process their input.
Maybe I'm missing something here, but I thought that the whole point of
writing our own parser was to avoid this.
