Re: [Qemu-devel] [PATCH 0/9] Our QAPI parser is a hack, replace it

[Anthony Liguori <aliguori@us.ibm.com>]

Markus Armbruster <armbru@redhat.com> writes:

> Anthony Liguori <aliguori@us.ibm.com> writes:
>
>> Markus Armbruster <armbru@redhat.com> writes:
>>
>>> If you think I'm exaggerating, check out the list of issues in PATCH
>>> 3/9.
>>
>> You are not.
>>
>> However, I think we can drop the whole thing and just use the JSON
>> module in Python.  The bit below seems to work:
>>
>>   import json.decoder, re
>>   from ordereddict import OrderedDict
>>   
>>   WHITESPACE = re.compile(r'(#.*\n|[ \r\t\n]*)*', re.MULTILINE)
>>   
>>   def make_object(pairs):
>>       return OrderedDict(pairs)
>>   
>>   def qapi_parse(data):
>>       _w = WHITESPACE.match
>>       idx = 0
>>       while idx < len(data):
>>           idx = _w(data, idx).end()
>>           if idx == len(data):
>>               break
>>           decoder = json.decoder.JSONDecoder(object_pairs_hook=make_object)
>>           obj, idx = decoder.raw_decode(data, idx)
>>           yield obj
>>   
>>   if __name__ == '__main__':
>>       with open('qapi-schema.json', 'r') as fp:
>>           data = fp.read().replace("'", '"')
>>   
>>       exprs = list(qapi_parse(data))
>>       print exprs
>
> I tried to find a way to use JSONDecoder, but not hard enough,
> apparently.
>
> The fp.read().replace("'", '"') is no good, because it blindly replaces
> within strings, such as 'the cat\'s meow'.
>
> Can your code handle comments between arbitrary tokens?  I suspect they
> work only between top-level expressions, but I could be wrong; Python
> isn't my strongest language, and I didn't test this.

It cannot.  The python JSON module has an optimized C implementation
which is less flexible than the python one.  Unfortunately it looks like
at least in my copy of python, the python version has bitrotted.

OTOH, the warnings are very clear when you attempt to do this.

Regards,

Anthony Liguori