Re: [PATCH v6 17/19] qapi/introspect.py: Type _gen_tree variants as Sequence[str]

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> Optional[List] is clunky; an empty sequence can more elegantly convey
> "no variants". By downgrading "List" to "Sequence", we can also accept
> tuples; this is useful for the empty tuple specifically, which we may
> use as a default parameter because it is immutable.
>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  scripts/qapi/introspect.py | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
> index 649225988d1..e4d31a59503 100644
> --- a/scripts/qapi/introspect.py
> +++ b/scripts/qapi/introspect.py
> @@ -247,13 +247,13 @@ def _use_type(self, typ: QAPISchemaType) -> str:
>          return self._name(typ.name)
>  
>      @staticmethod
> -    def _gen_features(features: List[QAPISchemaFeature]
> +    def _gen_features(features: Sequence[QAPISchemaFeature]
>                        ) -> List[Annotated[str]]:
>          return [Annotated(f.name, f.ifcond) for f in features]
>  
>      def _gen_tree(self, name: str, mtype: str, obj: Dict[str, object],
>                    ifcond: Sequence[str],
> -                  features: Optional[List[QAPISchemaFeature]]) -> None:
> +                  features: Sequence[QAPISchemaFeature] = ()) -> None:
>          """
>          Build and append a SchemaInfo object to self._trees.
>  
> @@ -261,7 +261,8 @@ def _gen_tree(self, name: str, mtype: str, obj: Dict[str, 
> object],
>          :param mtype: The entity's meta-type.
>          :param obj: Additional entity fields, as appropriate for the 
> meta-type.
>          :param ifcond: Sequence of conditionals that apply to this entity.
> -        :param features: Optional features field for SchemaInfo.
> +        :param features: Optional, The features field for SchemaInfo.

Downcase "The".

> +                         Will be omitted from the output if empty.
>          """
>          comment: Optional[str] = None
>          if mtype not in ('command', 'event', 'builtin', 'array'):
> @@ -298,7 +299,7 @@ def _gen_variant(self, variant: QAPISchemaVariant
>  
>      def visit_builtin_type(self, name: str, info: Optional[QAPISourceInfo],
>                             json_type: str) -> None:
> -        self._gen_tree(name, 'builtin', {'json-type': json_type}, [], None)
> +        self._gen_tree(name, 'builtin', {'json-type': json_type}, [])
>  
>      def visit_enum_type(self, name: str, info: Optional[QAPISourceInfo],
>                          ifcond: Sequence[str],
> @@ -316,7 +317,7 @@ def visit_array_type(self, name: str, info: 
> Optional[QAPISourceInfo],
>                           element_type: QAPISchemaType) -> None:
>          element = self._use_type(element_type)
>          self._gen_tree('[' + element + ']', 'array', {'element-type': 
> element},
> -                       ifcond, None)
> +                       ifcond)
>  
>      def visit_object_type_flat(self, name: str, info: 
> Optional[QAPISourceInfo],
>                                 ifcond: Sequence[str],

Marginal by itself.  Might be worth it as part of a more general move
away from Optional[List[...]].  See also next patch.