qemu/tests/qapi-schema/alternate-nested.json

# we reject a nested alternate branch
{ 'alternate': 'Alt1',
  'data': { 'name': 'str', 'value': 'int' } }
{ 'alternate': 'Alt2',
  'data': { 'nested': 'Alt1', 'b': 'bool' } }
qapi: Use 'alternate' to replace anonymous union Previous patches have led up to the point where I create the new meta-type "'alternate':'Foo'". See the previous patches for documentation; I intentionally split as much work into earlier patches to minimize the size of this patch, but a lot of it is churn due to testsuite fallout after updating to the new type. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> 2015-05-04 18:05:13 +03:00			`# we reject a nested alternate branch`
			`{ 'alternate': 'Alt1',`
qapi: Add some union tests Demonstrate that the qapi generator doesn't deal well with unions that aren't up to par. Later patches will update the expected reseults as the generator is made stricter. A few tests work as planned, but most show poor or missing error messages. Of particular note, qapi-code-gen.txt documents 'base' only for flat unions, but the tests here demonstrate that we currently allow a 'base' to a simple union, although it is exercised only in the testsuite. Later patches will remove this undocumented feature, to give us more flexibility in adding other future extensions to union types. For example, one possible extension is the idea of a type-safe simple enum, where added fields tie the discriminator to a user-defined enum type rather than creating an implicit enum from the names in 'data'. But adding such safety on top of a simple enum with a base type could look ambiguous with a flat enum; besides, the documentation also mentions how any simple union can be represented by an equivalent flat union. So it will be simpler to just outlaw support for something we aren't using. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> 2015-05-04 18:05:05 +03:00			`'data': { 'name': 'str', 'value': 'int' } }`
qapi: Use 'alternate' to replace anonymous union Previous patches have led up to the point where I create the new meta-type "'alternate':'Foo'". See the previous patches for documentation; I intentionally split as much work into earlier patches to minimize the size of this patch, but a lot of it is churn due to testsuite fallout after updating to the new type. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> 2015-05-04 18:05:13 +03:00			`{ 'alternate': 'Alt2',`
qapi: Add tests for empty unions The documentation claims that alternates are useful for allowing two or more types, although nothing enforces this. Meanwhile, it is silent on whether empty unions are allowed. In practice, the generated code will compile, in part because we have a 'void *data' branch; but attempting to visit such a type will cause an abort(). While there's no technical reason that a degenerate union could not be made to work, it's harder to justify the time spent in chasing known (the current abort() during visit) and unknown corner cases, than it would be to just outlaw them. A future patch will probably take the approach of forbidding them; in the meantime, we can at least add testsuite coverage to make it obvious where things stand. In addition to adding tests to expose the problems, we also need to adjust existing tests that are meant to test something else, but which could fail for the wrong reason if we reject degenerate alternates/unions. Note that empty structs are explicitly supported (for example, right now they are the only way to specify that one branch of a flat union adds no additional members), and empty enums are covered by the testsuite as working (even if they do not seem to have much use). Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1443565276-4535-8-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> 2015-09-30 01:21:05 +03:00			`'data': { 'nested': 'Alt1', 'b': 'bool' } }`