Re: [Qemu-devel] [PATCH v5 01/28] qapi: Document type-safety considerations

[Kevin Wolf <kwolf@redhat.com>]

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Am 31.03.2015 um 19:07 hat Eric Blake geschrieben:
> On 03/31/2015 09:09 AM, Kevin Wolf wrote:
> > Am 24.03.2015 um 21:03 hat Eric Blake geschrieben:
> >> Go into more details about the various types of valid expressions
> >> in a qapi schema, including tweaks to document fixes being done
> >> later in the current patch series.  Also fix some stale and missing
> >> documentation in the QMP specification.
> >>
> >> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> >> +A flat union definition specifies a complex type as its base, and
> >> +avoids nesting on the wire.  In this case, the fields of the complex
> >> +type are included as top-level fields of the union dictionary in the
> >> +QMP wire format, and the 'discriminator' field must be the name of an
> >> +enum-typed member of the base type. An example definition is:
> > 
> > Adding full context:
> > 
> >      { 'type': 'BlockdevCommonOptions', 'data': { 'readonly': 'bool' } }
> >      { 'union': 'BlockdevOptions',
> >        'base': 'BlockdevCommonOptions',
> >        'data': { 'raw': 'RawOptions',
> >                  'qcow2': 'Qcow2Options' } }
> 
> Oh, yikes.  I even outlawed this type of "simple union with base class"
> later in the series, since no one was using it, and since it gets in the
> way of my desire to move towards "simple union with type-safe enum
> branching".  I'll have to revisit that text and document an actual flat
> union in v6.

There is already an example for a real flat union. You just need to drop
this one and probably change the text around it a bit.

Kevin

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