Re: [PATCH v3 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>

[...]

> diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
> index e97c978d38..39c91af245 100644
> --- a/scripts/qapi/schema.py
> +++ b/scripts/qapi/schema.py
> @@ -933,8 +933,11 @@ def connect_doc(self, doc: Optional[QAPIDoc]) -> None:
>  class QAPISchemaFeature(QAPISchemaMember):
>      role = 'feature'
>  
> +    # Features which are standardized across all schemas
> +    SPECIAL_NAMES = ['deprecated', 'unstable']
> +
>      def is_special(self) -> bool:
> -        return self.name in ('deprecated', 'unstable')
> +        return self.name in QAPISchemaFeature.SPECIAL_NAMES
>  
>  
>  class QAPISchemaObjectTypeMember(QAPISchemaMember):
> @@ -1138,6 +1141,16 @@ def __init__(self, fname: str):
>          self._entity_list: List[QAPISchemaEntity] = []
>          self._entity_dict: Dict[str, QAPISchemaDefinition] = {}
>          self._module_dict: Dict[str, QAPISchemaModule] = OrderedDict()
> +        # NB, values in the dict will identify the first encountered
> +        #     usage of a named feature only

Unusual indentation within the comment.  Can tidy up in my tree.

> +        self._feature_dict: Dict[str, QAPISchemaFeature] = OrderedDict()
> +
> +        # All schemas get the names defined in the QapiSpecialFeature enum.
> +        # Use of OrderedDict ensures they are emitted first when generating
> +        # the enum definition, thus matching QapiSpecialFeature.

Actually, even plain dict ensures that since 3.6 de facto, and since 3.7
de jure.  OrderedDict additionally permits changing the order, but we
don't use that.  I have a patch to get rid of OrderedDict as part of a
not quite finishes series of simplifications for Python 3.8.

Perhaps the easiest way forward is not to worry about this here and now,
and instead clean it up with along with the other uses of OrderedDict.

> +        for f in QAPISchemaFeature.SPECIAL_NAMES:
> +            self._feature_dict[f] = QAPISchemaFeature(f, None)
> +
>          self._schema_dir = os.path.dirname(fname)
>          self._make_module(QAPISchemaModule.BUILTIN_MODULE_NAME)
>          self._make_module(fname)

[...]