IDL: Enumeration support in union types

Source/bindings/scripts/v8_union.py

Index: Source/bindings/scripts/v8_union.py
diff --git a/Source/bindings/scripts/v8_union.py b/Source/bindings/scripts/v8_union.py
index f0b696a582f9f34b85250b88ef02d80618b9e558..52b8e1f4a5fbd388c9730e5fdb4980bc7aa69257 100644
--- a/Source/bindings/scripts/v8_union.py
+++ b/Source/bindings/scripts/v8_union.py
@@ -70,6 +70,7 @@ def container_context(union_type, interfaces_info):
     array_or_sequence_type = None
     boolean_type = None
     dictionary_type = None
+    enum_type = None
     interface_types = []
     numeric_type = None
     string_type = None
@@ -95,11 +96,17 @@ def container_context(union_type, interfaces_info):
             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)
@@ -118,13 +125,14 @@ def container_context(union_type, interfaces_info):
         '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),
     }
 
 
@@ -143,6 +151,7 @@ def member_context(member, interfaces_info):
         '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,