On 05/05/2014 07:30 PM, Fam Zheng wrote:
>> NAME: { 'type': TYPE, 'default': DEFAULT }
>>
>> where
>>
>> NAME: { 'type': TYPE }
>>
>> can be abbreviated to
>>
>> NAME: TYPE
>
> In data definition, we allow inline sub-structure:
>
> { 'type': 'VersionInfo',
> 'data': {'qemu': {'major': 'int', 'minor': 'int', 'micro': 'int'},
> 'package': 'str'} }
>
> If we allow properties as a dict, we need to disambiguate properly from the
> above case. Proposing:
>
> MAGIC: { 'name': NAME, 'type: TYPE, 'default': DEFAULT }
Oh, good catch. The alternative is to drop all instances of inline
sub-structs. Searching for 'data.*{.*{', I found only VersionInfo and
PciBridgeInfo; I then did a full manual search of qapi-schema.json and
only found the additional instance of PciDeviceInfo where the sub-struct
is not on the same line as the initial { of the 'data'. Just getting
rid of inlined sub-structs may be quite feasible.
On a related vein, there are a number of types that aren't merely a
string name. For example:
{ 'command': 'migrate-set-capabilities',
'data': { 'capabilities': ['MigrationCapabilityStatus'] } }
and similar, where we have an array type rather than a raw string type
name. But at least with that, NAME: { 'type': [ 'array' ] } is still a
reasonable parse.
The problem with MAGIC:{'name'...} is that you need to express more than
one parameter, but as a dict, you can't reuse the same MAGIC more than
once. That is:
'data': { MAGIC : { 'name': 'qemu', 'type': { 'major'...} },
MAGIC : { 'name': 'package', 'type', 'str' } } }
proves that you have to have two distinct MAGIC in the same 'data', so
'' for both is out.
>
> Where MAGIC should NOT be something that is a valid NAME from current schema.
> Some ideas:
>
> - Special string, that has invalid chars as a identifier, like '*', '%', '&',
> etc, or simply an empty str ''.
> Of course we need to enforce the checking and distinguishing in
> scripts/qapi-types.py.
>
> - Non-string: current NAME must be a string, any type non-string could be
> distinguished from NAME, like number, bool, null, []. But its meaning could
> be confusing to reviewer.
>
> - Special symbol: we can define a dedicate symbol for this, like the literal
> TYPE, in the schema. But this way we deviate more from JSON.
Also, while we aren't strict JSON, it's nice that we're still fairly
close to JSON5, and worth keeping that property.
>
> Personally, I think empty str '' makes more sense for me. What do you think?
>
At this point, I'm leaning towards dropping support for unnamed inlined
sub-structs.
> Anyway we only add things, so we will keep the '*name' suger.
>
> Thanks,
> Fam
>
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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