qemu/tests/qapi-schema/args-boxed-empty.json

# 'boxed' requires a non-empty type
{ 'struct': 'Empty', 'data': {} }
{ 'command': 'foo', 'boxed': true, 'data': 'Empty' }
qapi: Implement boxed types for commands/events Turn on the ability to pass command and event arguments in a single boxed parameter, which must name a non-empty type (although the type can be a struct with all optional members). For structs, it makes it possible to pass a single qapi type instead of a breakout of all struct members (useful if the arguments are already in a struct or if the number of members is large); for other complex types, it is now possible to use a union or alternate as the data for a command or event. The empty type may be technically feasible if needed down the road, but it's easier to forbid it now and relax things to allow it later, than it is to allow it now and have to special case how the generated 'q_empty' type is handled (see commit 7ce106a9 for reasons why nothing is generated for the empty type). An alternate type is never considered empty, but now that a boxed type can be either an object or an alternate, we have to provide a trivial QAPISchemaAlternateType.is_empty(). The new call to arg_type.is_empty() during QAPISchemaCommand.check() requires that we first check the type in question; but there is no chance of introducing a cycle since objects do not refer back to commands. We still have a split in syntax checking between ad-hoc parsing up front (merely validates that 'boxed' has a sane value) and during .check() methods (if 'boxed' is set, then 'data' must name a non-empty user-defined type). Generated code is unchanged, as long as no client uses the new feature. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1468468228-27827-10-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> [Test files renamed to -boxed-] Signed-off-by: Markus Armbruster <armbru@redhat.com> 2016-07-14 11:50:20 +08:00			`# 'boxed' requires a non-empty type`
			`{ 'struct': 'Empty', 'data': {} }`
			`{ 'command': 'foo', 'boxed': true, 'data': 'Empty' }`