Re: [Qemu-devel] [PATCH v7 06/14] qapi: Create simple union type member earlier

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> For simple unions, we were creating the implicit 'type' tag
> member during the QAPISchemaObjectTypeVariants constructor.
> This is different from every other implicit QAPISchemaEntity
> object, which get created by QAPISchema methods.  Hoist the
> creation to the caller (renaming _make_tag_enum() to
> _make_implicit_tag()), and pass the entity rather than the
> string name, so that we have the nice property that no
> entities are created as a side effect within a different
> entity.  A later patch will then have an easier time of
> associating location info with each entity creation.
>
> No change to generated code.
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v7: Rework assertions, rename to _make_implicit_tag()
> v6: New patch
> ---
>  scripts/qapi.py | 29 +++++++++++++++--------------
>  1 file changed, 15 insertions(+), 14 deletions(-)
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index b1134b8..eaa43b8 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -1033,18 +1033,18 @@ class QAPISchemaObjectTypeMember(object):
>
>
>  class QAPISchemaObjectTypeVariants(object):
> -    def __init__(self, tag_name, tag_enum, variants):
> -        assert tag_name is None or isinstance(tag_name, str)
> -        assert tag_enum is None or isinstance(tag_enum, str)
> +    def __init__(self, tag_name, tag_member, variants):
> +        # Flat unions pass tag_name but not tag_member.
> +        # Simple unions and alternates pass tag_member but not tag_name.
> +        # After check(), tag_member is always set, and tag_name remains
> +        # a reliable witness of being used by a flat union.
> +        assert bool(tag_member) != bool(tag_name)
> +        assert (isinstance(tag_name, str) or
> +                isinstance(tag_member, QAPISchemaObjectTypeMember))
>          for v in variants:
>              assert isinstance(v, QAPISchemaObjectTypeVariant)
>          self.tag_name = tag_name
> -        if tag_name:
> -            assert not tag_enum
> -            self.tag_member = None
> -        else:
> -            self.tag_member = QAPISchemaObjectTypeMember('type', tag_enum,
> -                                                         False)
> +        self.tag_member = tag_member
>          self.variants = variants
>
>      def check(self, schema, members, seen):
> @@ -1251,9 +1251,10 @@ class QAPISchema(object):
>              typ, 'wrapper', [self._make_member('data', typ, info)])
>          return QAPISchemaObjectTypeVariant(case, typ)
>
> -    def _make_tag_enum(self, type_name, variants):
> -        return self._make_implicit_enum_type(type_name,
> -                                             [v.name for v in variants])
> +    def _make_implicit_tag(self, type_name, variants):
> +        typ = self._make_implicit_enum_type(type_name,
> +                                            [v.name for v in variants])
> +        return QAPISchemaObjectTypeMember('type', typ, False)
>
>      def _def_union_type(self, expr, info):
>          name = expr['union']
> @@ -1267,7 +1268,7 @@ class QAPISchema(object):
>          else:
>              variants = [self._make_simple_variant(key, value, info)
>                          for (key, value) in data.iteritems()]
> -            tag_enum = self._make_tag_enum(name, variants)
> +            tag_enum = self._make_implicit_tag(name, variants)

Rename tag_enum to tag_member or tag?

>          self._def_entity(
>              QAPISchemaObjectType(name, info, base,
>                                   self._make_members(OrderedDict(), info),
> @@ -1280,7 +1281,7 @@ class QAPISchema(object):
>          data = expr['data']
>          variants = [self._make_variant(key, value)
>                      for (key, value) in data.iteritems()]
> -        tag_enum = self._make_tag_enum(name, variants)
> +        tag_enum = self._make_implicit_tag(name, variants)
>          self._def_entity(
>              QAPISchemaAlternateType(name, info,
>                                      QAPISchemaObjectTypeVariants(None,

Likewise.