Re: [Qemu-devel] [PATCH 2/3] qapi.py: Allow top-level type reference for command definitions

[Kevin Wolf]

Am 21.06.2013 um 12:30 hat Eric Blake geschrieben:
> On 06/19/2013 05:28 PM, Kevin Wolf wrote:
> > If 'data' for a command definition isn't a dict, but a string, it is
> > taken as a (struct) type name and the fields of this struct are directly
> > used as parameters.
> 
> I like it!  I suspect it may cause conflicts with Amos' work on adding
> introspection, but it is still worth doing.
> 
> >  
> >  def parse_args(typeinfo):
> > +    if isinstance(typeinfo, basestring):
> > +        struct = find_struct(typeinfo)
> > +        assert struct != None
> > +        typeinfo = struct['data']
> > +
> 
> Does this mean that .json files must be written in topological order (in
> that we can't use 'data':'Type' unless 'Type' was declared earlier in
> the file)?

No, you have effectively two passes: First the qapi.py function reads in
the file and adds any structs, enums and unions to the respective lists
and returns something like an array of all objects found. The generator
scripts then filter that array for the type of objects they want (e.g.
only commands, or only types) and indirectly call parse_args(). At this
point all types have already been registered.

> As the .json file gets larger, I've been wondering if
> enforcing alphabetical ordering would make it easier to manage; but if
> topological sorting is required, alphabetical sorting might not always
> be possible.

Yeah, possibly. Another thing I was considering is introducing include
files, so that I could for example specify { 'include':
'block/qapi-schema.json' } and have all block-related things separated
in this file.

Kevin