Re: [Qemu-devel] [PATCH 1/2] qapi: Add comments to aid debugging generated introspection

[Eric Blake <eblake@redhat.com>]

On 07/02/2018 01:43 PM, Markus Armbruster wrote:
> Eric Blake <eblake@redhat.com> writes:
> 
>> On 06/29/2018 02:55 PM, Eric Blake wrote:
>>> We consciously chose in commit 1a9a507b to hide QAPI type names
>>> from the generated introspection output, but added a command line
>>> option -u to unmask the type name when doing a debug build.  At
>>> that time, we generated a monolithic C string, so there was no
>>> better way to do things (we could not really inject comments).
>>>
>>> Later, in commit 7d0f982b, we switched the generation to output
>>> a QLit object, in part to make it easier for future addition of
>>> conditional compilation.  But this switch has also made it easier
>>> to interject strategic comments.  That commit also forgot to
>>> delete some now-stale comments about long generated line lengths.
>>>
>>> For now, type name debug aid comments are only output once per
>>> meta-type, rather than at all uses of the number used to encode
>>> the type to the introspection data.  But this is still a lot
>>> more convenient than having to regenerate the file with the
>>> unmask operation temporarily turned on.
>> ...

> to_qlit() converts from a natural representation of JSON in Python to
> JSON text.
> 
> Your patch breaks it for JSON objects that have a member named
> 'comment'.

Hmm.  None do, presently.  And I don't see where it would be permitted 
in the QAPI schema for query-qmp-schema.

> 
> Related work: Marc-André's "[PATCH v6 09/15] qapi-introspect: add
> preprocessor conditions to generated QLit" uses tuples to augment JSON.
> He uses them for conditionals, but the technique could be generalized,
> say from his (jobj, ifcond) to (jobj, { 'if': ifcond, '#': comment }.

Yeah, I can probably rebase on top of that (and at this point, it's late 
enough to probably have missed 3.0 anyways, so I'm not time-crunched for 
getting it done right now).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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