Re: [PATCH v4 4/4] qapi: expose all schema features to code

[Markus Armbruster <armbru@redhat.com>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> This replaces use of the constants from the QapiSpecialFeatures
> enum, with constants from the auto-generate QapiFeatures enum
> in qapi-features.h
>
> The 'deprecated' and 'unstable' features still have a little bit of
> special handling, being force defined to be the 1st + 2nd features
> in the enum, regardless of whether they're used in the schema. This
> retains compatibility with common code that references the features
> via the QapiSpecialFeatures constants.
>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Daniel, feel free to ignore this at least for now.  I'm trying to learn
some typing lore from John.

v3 made mypy unhappy.  I asked John for advice, and also posted a
solution involving ValuesView I hacked up myself.  Daniel took it for
v4.

John suggested to use List.

I now wonder whether could use Iterable.

I'll show the three solutions inline.

John, thoughts?

[...]

> diff --git a/scripts/qapi/features.py b/scripts/qapi/features.py
> new file mode 100644
> index 0000000000..be3e5d03ff
> --- /dev/null
> +++ b/scripts/qapi/features.py
> @@ -0,0 +1,51 @@
> +"""
> +QAPI features generator
> +
> +Copyright 2024 Red Hat
> +
> +This work is licensed under the terms of the GNU GPL, version 2.
> +# See the COPYING file in the top-level directory.
> +"""
> +
> +from typing import Dict, ValuesView
> +
> +from .common import c_enum_const, c_name
> +from .gen import QAPISchemaMonolithicCVisitor
> +from .schema import (
> +    QAPISchema,
> +    QAPISchemaFeature,
> +)
> +
> +
> +class QAPISchemaGenFeatureVisitor(QAPISchemaMonolithicCVisitor):
> +
> +    def __init__(self, prefix: str):
> +        super().__init__(
> +            prefix, 'qapi-features',
> +            ' * Schema-defined QAPI features',
> +            __doc__)
> +
> +        self.features: ValuesView[QAPISchemaFeature]

This is the ValuesView solution.

The List solution:

           self.features: List[QAPISchemaFeature] = []

The Iterable solution:

           self.features: Iterable[QAPISchemaFeature]

[...]


> diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
> index e97c978d38..7f70969c09 100644
> --- a/scripts/qapi/schema.py
> +++ b/scripts/qapi/schema.py

[...]

> @@ -1147,6 +1161,9 @@ def __init__(self, fname: str):
>          self._def_exprs(exprs)
>          self.check()
>  
> +    def features(self) -> ValuesView[QAPISchemaFeature]:
> +        return self._feature_dict.values()

This is the ValuesView solution.

The List solution:

       def features(self) -> List[QAPISchemaFeature]:
           return list(self._feature_dict.values())

The Iterable solution:

       def features(self) -> Iterable[QAPISchemaFeature]:
           return self._feature_dict.values()


> +
>      def _def_entity(self, ent: QAPISchemaEntity) -> None:
>          self._entity_list.append(ent)
>  

[...]