Re: [Qemu-devel] [PATCH v4 2/3] qapi: Add a primitive to include other files from a QAPI schema file

[Eric Blake <eblake@redhat.com>]

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On 03/03/2014 08:27 AM, Markus Armbruster wrote:

>>>> +The QAPI schema definitions can be modularized using the 'include'
>>>> directive:
>>>> +
>>>> + include("sub-system/qapi.json")
>>
>>> And now it isn't JSON anymore.
>>
>>> To keep it JSON, use syntax like
>>
>>>     { "include": "sub-system/qapi.json" }

I actually think this looks nicer - makes the file more consistent.

>>
>>> If you absolutely must make it non-JSON, you better rename the .json
>>> files.
>>
>>> Hmm, we already are non-JSON, because we use ' instead of " for no sane
>>> reason.

A weak argument: ' is easier than " to type (at least on US keyboards -
no shift key required).

Another weak argument: using ' in the qapi files vs. " in actual QMP
makes it easy to interleave discussions about semantics vs. examples of
those semantics in use (you can see whether a code snippet is talking
about qapi or wire format based on what quoting it used)

Our files are already non-JSON due to comments (JSON has no notion of #
introducing a comment to ignore text to the next newline).  But both our
use of comments and our use of ' instead of " can be remedied in a
one-pass sed script to get a true JSON output if such is needed, at
least as long as we don't need to quote any " characters in the schema.

Therefore, I agree that making the include syntax closer to true JSON is
desirable, whether or not we also decide to use " in the files to begin
with.  I don't see any way around the fact that JSON doesn't define
comments, vs. our absolute need for comments in our schema files, though.

>>
>>> Our JSON parser accepts ' as an extension, to save us quoting in C
>>> strings.  That reason doesn't apply to .json files.
>>
>> Is it a problem if they are not pure JSON? In the end, they are parsed by
>> qapi.py (which already knows about file syntax), and having a separate syntax
>> for includes makes it somewhat easier to spot when that happens.
> 
> I don't particularly care whether schema syntax is pure JSON, some
> bastardized variation of JSON, or something else entirely.  But as long
> as we advertize schema files it as .json, they better contain JSON.  If
> they contain something else, they should be called something else.

Maybe .qapi? But the name qapi-schema.qapi sounds redundant...

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


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