Re: [Qemu-devel] [PATCH] full introspection support for QMP

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

Eric Blake <eblake@redhat.com> writes:

> On 07/02/2013 11:01 AM, Paolo Bonzini wrote:
>>>> Arguably that rule of thumb would apply equally to the QEMU
>>>> build scripts which already parse qapi-schema.json. It could
>>>> be possible to normalize qapi-schema.json somewhat to remove
>>>> this 2-stage parsing if we went down this route.
>>>
>>> Indeed, I wouldn't mind a one-time pass over qapi-schema.json to make it
>>> follow a more rigid format if that made it easier to use it as-is with
>>> less post-processing.  It won't be very nice to backport such a
>>> conversion, but I don't know how much distros are planning on
>>> backporting introspection in the first place.
>> 
>> How would the schema look like after this "one-time pass"?
>> 
>> This:
>> 
>>> [
>>>          { "name": "protocol",
>>>            "type": "str" },
>>>          { "name": "fdname",
>>>            "type": "str" },
>>>          { "name": "skipauth",
>>>            "type": "bool",
>>>            "optional": true },
>>>          { "name": "tls",
>>>            "type": "bool",
>>>            "optional": true }
>>> ]
>> 
>> Looks quite awful for a human to write and read.
>
> Which puts us back in favor of my original argument that keeping
> qapi-schema.json compact for human use,

qapi-schema.json is not "for human use".  It's consumed by QAPI.  It
happens to be reasonably human readable but that's just a happy
coincidence and because we document and format the heck out of it.

> while expanding the QMP output
> to be verbose for machine use, is probably what we'll have to live with.
>  While it is easy to document shortcuts that the qapi parser can use
> when converting .json to code, it is harder to require that all other
> QMP clients must implement those same shortcuts, instead of having
> things already directly represented.

qapi-schema.json is valid JSON except for the # style comments.  Those
are trivial to remove and we could simply post process it.

Heck, if you use json_parser to parse the file, you'd end up with a list
of QObjects that could be returned directly via QMP.

I don't understand what all this talk of "post-processing" is.

Regards,

Anthony Liguori

>
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org