Re: [Qemu-devel] [PATCH v11 22/28] qapi: Simplify visiting of alternate types

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Previously, working with alternates required two lookup arrays
> and some indirection: for type Foo, we created Foo_qtypes[]
> which maps each qtype to a value of the generated FooKind enum,
> then look up that value in FooKind_lookup[] like we do for other
> union types.
[...]
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index d4ef08e..1790e8f 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -627,15 +627,15 @@ def check_union(expr, expr_info):
>  def check_alternate(expr, expr_info):
>      name = expr['alternate']
>      members = expr['data']
> -    values = {'MAX': '(automatic)'}
> +    values = {}
>      types_seen = {}
>
>      # Check every branch
>      for (key, value) in members.items():
>          check_name(expr_info, "Member of alternate '%s'" % name, key)
>
> -        # Check for conflicts in the generated enum
> -        c_key = camel_to_upper(key)
> +        # Check for conflicts in the branch names
> +        c_key = c_name(key)
>          if c_key in values:
>              raise QAPIExprError(expr_info,
>                                  "Alternate '%s' member '%s' clashes with 
> '%s'"
> @@ -1090,8 +1090,11 @@ class QAPISchemaObjectTypeVariants(object):
>          assert isinstance(self.tag_member.type, QAPISchemaEnumType)
>          for v in self.variants:
>              v.check(schema)
> -            assert v.name in self.tag_member.type.values
> -            if isinstance(v.type, QAPISchemaObjectType):
> +            # Union names must match enum values; alternate names are
> +            # checked separately. Use 'seen' to tell the two apart.
> +            if seen:
> +                assert v.name in self.tag_member.type.values
> +                assert isinstance(v.type, QAPISchemaObjectType)
>                  v.type.check(schema)
>
>      def check_clash(self, schema, info, seen):
> @@ -1133,6 +1136,11 @@ class QAPISchemaAlternateType(QAPISchemaType):
>          # Not calling self.variants.check_clash(), because there's nothing
>          # to clash with
>          self.variants.check(schema, {})
> +        # Alternate branch names have no relation to the tag enum values;
> +        # so we have to check for potential name collisions ourselves.
> +        cases = {}
> +        for var in self.variants.variants:
> +            var.check_clash(self.info, cases)

Nitpick: elsewhere in this file, we use "for v" to iterate over
variants.

>
>      def json_type(self):
>          return 'value'
> @@ -1340,7 +1348,7 @@ class QAPISchema(object):
>          data = expr['data']
>          variants = [self._make_variant(key, value)
>                      for (key, value) in data.iteritems()]
> -        tag_member = self._make_implicit_tag(name, info, variants)
> +        tag_member = QAPISchemaObjectTypeMember('type', 'QTypeCode', False)
>          self._def_entity(
>              QAPISchemaAlternateType(name, info,
>                                      QAPISchemaObjectTypeVariants(None,
[...]