Re: [PATCH v4 30/34] qapi: Implement deprecated-output=hide for QMP event data

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> On 3/17/20 6:54 AM, Markus Armbruster wrote:
>> This policy suppresses deprecated bits in output, and thus permits
>> "testing the future".  Implement it for QMP event data: suppress
>> deprecated members.
>>
>> No QMP event data is deprecated right now.
>>
>> Signed-off-by: Markus Armbruster <address@hidden>
>> ---
>
>> +static void test_event_deprecated_data(TestEventData *data, const void 
>> *unused)
>> +{
>> +    memset(&compat_policy, 0, sizeof(compat_policy));
>> +
>> +    data->expect = qdict_from_jsonf_nofail("{ 'event': 
>> 'TEST-EVENT-FEATURES0',"
>> +                                           " 'data': { 'foo': 42 } }");
>> +    qapi_event_send_test_event_features0(42);
>> +    g_assert(data->emitted);
>> +
>> +    qobject_unref(data->expect);
>> +
>> +    compat_policy.deprecated_output = COMPAT_POLICY_OUTPUT_HIDE;
>
> Again, playing fast-and-loose with compat_policy.has_deprecated_output.

I'll clean it up.

>> +++ b/scripts/qapi/events.py
>> @@ -104,7 +104,7 @@ def gen_event_send(name, arg_type, features, boxed,
>>         if have_args:
>>           ret += mcgen('''
>> -    v = qobject_output_visitor_new(&obj);
>> +    v = qobject_output_visitor_new_qmp(&obj);
>>   ''')
>>           if not arg_type.is_implicit():
>>               ret += mcgen('''
>> @@ -123,7 +123,11 @@ def gen_event_send(name, arg_type, features, boxed,
>>           ret += mcgen('''
>>         visit_complete(v, &obj);
>> -    qdict_put_obj(qmp, "data", obj);
>> +    if (qdict_size(qobject_to(QDict, obj))) {
>> +        qdict_put_obj(qmp, "data", obj);
>> +    } else {
>> +        qobject_unref(obj);
>> +    }
>
> So you'd rather omit data altogether than emit "data":{} when all
> deprecated members disappear.  Fair enough; both approaches work.

I initially didn't do this until my testing demonstrated that "data"
goes away entirely when I delete the last member from the schema.  To
actually fulfill the "test the future" mission, I need policy hide drop
data, too.

> Reviewed-by: Eric Blake <address@hidden>

Thanks!