Re: [PATCH v2 10/16] scripts/qapi: add QAPISchemaType.is_predefined

Markus Armbruster
2026-02-25T07:33:47Z

Paolo Bonzini <pbonzini@redhat.com> writes:

> It is impossible to call is_implicit on an enum type from the visitor, because
> the QAPISchemaEnumType has already been exploded into its costituent fields.

constituent

Passing selected attributes instead of the entire object to its visitor
method limits what the visitor can do. This is both good and bad.
We've run into "bad" a couple of times. It's never been bad enough to
change the interface, though.

Thoughts?

> The Rust backend is also not modular (yet?) so it is not possible to filter
> out the builtin module;

Really?

The visitors are all based on QAPISchemaVisitor. Protocol:

.visit_begin()
for all modules:
.visit_module()
for all entities:
if .visit_needed():
.visit_FOO()
.visit_end()

QAPISchemaModularCVisitor implements .visit_module() to generate code
per module. Its .write() skips builtin modules unless opt_builtins.

QAPISchemaMonolithicCVisitor is oblivious of modules: it doesn't
implement .visit_module(), and writes out everything. This is fine,
because we use it only to generate qapi-features.[ch] and
qapi-introspect.[ch]. Generating the former has no need for recognizing
the built-ins because there are no built-in features. Generating the
latter has no need because it treats built-in stuff exactly like
user-defined stuff.

QAPISchemaRsVisitor [PATCH 12] also doesn't implement .visit_module().
It uses QAPISchema.is_predefined(), defined in this patch, to skip
built-in. Could it rely on .visit_module() instead?

> add a way to query for implicit type names without
> having the object itself.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> scripts/qapi/schema.py | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
> index 848a7401251..15f5d97418f 100644
> --- a/scripts/qapi/schema.py
> +++ b/scripts/qapi/schema.py
> @@ -1243,6 +1243,17 @@ def _def_builtin_type(
> # schema.
> self._make_array_type(name, None)
>
> + def is_predefined(self, name: str) -> bool:
> + # See QAPISchema._def_predefineds()
> + entity = self._entity_dict[name]
> + if isinstance(entity, QAPISchemaBuiltinType):
> + return True
> + if entity is self.the_empty_object_type:
> + return True
> + if name == 'QType':
> + return True
> + return False
> +
> def _def_predefineds(self) -> None:
> for t in [('str', 'string', 'char' + POINTER_SUFFIX),
> ('number', 'number', 'double'),