IDL: Enumeration support in union types

Source/bindings/scripts/v8_union.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import v8_utilities
 
 
 UNION_H_INCLUDES = frozenset([
     'bindings/core/v8/Dictionary.h',
     'bindings/core/v8/ExceptionState.h',
@@ skipping 52 matching lines @@
 def container_context(union_type, interfaces_info):
     members = []
 
     # These variables refer to member contexts if the given union type has
     # corresponding types. They are used for V8 -> impl conversion.
     array_buffer_type = None
     array_buffer_view_type = None
     array_or_sequence_type = None
     boolean_type = None
     dictionary_type = None
+    enum_type = None
     interface_types = []
     numeric_type = None
     string_type = None
     for member in union_type.member_types:
         context = member_context(member, interfaces_info)
         members.append(context)
         if member.base_type == 'ArrayBuffer':
             if array_buffer_type:
                 raise Exception('%s is ambiguous.' % union_type.name)
             array_buffer_type = context
         elif member.base_type == 'ArrayBufferView':
             if array_buffer_view_type:
                 raise Exception('%s is ambiguous.' % union_type.name)
             array_buffer_view_type = context
         # FIXME: Remove generic Dictionary special casing.
         elif member.is_dictionary or member.base_type == 'Dictionary':
             if dictionary_type:
                 raise Exception('%s is ambiguous.' % union_type.name)
             dictionary_type = context
         elif member.is_array_or_sequence_type:
             if array_or_sequence_type:
                 raise Exception('%s is ambiguous.' % union_type.name)
             array_or_sequence_type = context
         elif member.is_interface_type:
             interface_types.append(context)
+        elif member.is_enum:

[Jens Widell, 2015/01/16 09:53:51]

If there's an enum type in the union, it will be union_type.string_member_type,
and reading string_member_type would throw an error (about ambiguity) if there's
both an enum and some other string.

So the additions here in this loop aren't really needed; we could could later
check if string_type.is_enum is true.

In fact, I think all the added handling of enumerations in this function is
unneeded; handling the enum validation expression in member_context() would be
enough.

[bashi, 2015/01/16 10:11:58]

My understanding is that enums and strings are not distinguishable and that's
why I added exceptions in line 101 and 109. However, it seems that the spec
doesn't explicitly say that, so maybe we need to file a bug for the spec. 
http://heycam.github.io/webidl/#dfn-distinguishable
Hmm, does it mean we will provide getAsString() getter instead of getFooEnum()
for "enum FooEnum { ... }"? I'd prefer to provide the later.

+            if string_type:
+                raise Exception('%s is ambiguous.' % union_type.name)
+            enum_type = context
         elif member is union_type.boolean_member_type:
             boolean_type = context
         elif member is union_type.numeric_member_type:
             numeric_type = context
         elif member is union_type.string_member_type:
+            if enum_type:
+                raise Exception('%s is ambiguious.' % union_type.name)
             string_type = context
         else:
             raise Exception('%s is not supported as an union member.' % member.name)
 
     # Nullable restriction checks
     nullable_members = union_type.number_of_nullable_member_types
     if nullable_members > 1:
         raise Exception('%s contains more than one nullable members' % union_type.name)
     if dictionary_type and nullable_members == 1:
         raise Exception('%s has a dictionary and a nullable member' % union_type.name)
 
     return {
         'array_buffer_type': array_buffer_type,
         'array_buffer_view_type': array_buffer_view_type,
         'array_or_sequence_type': array_or_sequence_type,
         'boolean_type': boolean_type,
         'cpp_class': union_type.cpp_type,
         'dictionary_type': dictionary_type,
-        'type_string': str(union_type),
+        'enum_type': enum_type,
         'includes_nullable_type': union_type.includes_nullable_type,
         'interface_types': interface_types,
         'members': members,
         'needs_trace': any(member['is_traceable'] for member in members),
         'numeric_type': numeric_type,
         'string_type': string_type,
+        'type_string': str(union_type),
     }
 
 
 def member_context(member, interfaces_info):
     cpp_includes.update(member.includes_for_type)
     interface_info = interfaces_info.get(member.name, None)
     if interface_info:
         cpp_includes.update(interface_info.get('dependencies_include_paths', []))
         header_forward_decls.add(member.implemented_as)
     if member.is_nullable:
         member = member.inner_type
     return {
         'cpp_name': v8_utilities.uncapitalize(member.name),
         'cpp_type': member.cpp_type_args(used_in_cpp_sequence=True),
         'cpp_local_type': member.cpp_type,
         'cpp_value_to_v8_value': member.cpp_value_to_v8_value(
             cpp_value='impl.getAs%s()' % member.name, isolate='isolate',
             creation_context='creationContext'),
+        'enum_validation_expression': member.enum_validation_expression,
         'is_traceable': member.is_traceable,
         'rvalue_cpp_type': member.cpp_type_args(used_as_rvalue_type=True),
         'specific_type_enum': 'SpecificType' + member.name,
         'type_name': member.name,
         'v8_value_to_local_cpp_value': member.v8_value_to_local_cpp_value(
             {}, 'v8Value', 'cppValue', isolate='isolate',
             needs_exception_state_for_string=True),
     }