IDL: Support optional union type arguments with default values

Source/bindings/scripts/v8_methods.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 191 matching lines @@
                     # These allow null and undefined values, so a type-check is still required.
                     not idl_type.is_nullable and
                     not (argument.is_optional and
                          'Default' in extended_attributes))
 
     if ('ImplementedInPrivateScript' in extended_attributes and
         not idl_type.is_wrapper_type and
         not idl_type.is_basic_type):
         raise Exception('Private scripts supports only primitive types and DOM wrappers.')
 
-    default_cpp_value = argument.default_cpp_value
+    set_default_value = argument.set_default_value
     return {
         'cpp_type': idl_type.cpp_type_args(extended_attributes=extended_attributes,
                                            raw_type=True,
                                            used_as_variadic_argument=argument.is_variadic),
         'cpp_value': this_cpp_value,
         # FIXME: check that the default value's type is compatible with the argument's
-        'default_value': default_cpp_value,
+        'set_default_value': set_default_value,
         'enum_validation_expression': idl_type.enum_validation_expression,
         'handle': '%sHandle' % argument.name,
         # FIXME: remove once [Default] removed and just use argument.default_value
-        'has_default': 'Default' in extended_attributes or default_cpp_value,
+        'has_default': 'Default' in extended_attributes or set_default_value,
         'has_type_checking_interface': type_checking_interface,
         'has_type_checking_unrestricted':
             (has_extended_attribute_value(interface, 'TypeChecking', 'Unrestricted') or
              has_extended_attribute_value(method, 'TypeChecking', 'Unrestricted')) and
             idl_type.name in ('Float', 'Double'),
         # Dictionary is special-cased, but arrays and sequences shouldn't be
         'idl_type': idl_type.base_type,
         'idl_type_object': idl_type,
         'index': index,
         'is_callback_interface': idl_type.is_callback_interface,
@@ skipping 156 matching lines @@
     property_attributes_list = []
     if 'NotEnumerable' in extended_attributes:
         property_attributes_list.append('v8::DontEnum')
     if 'Unforgeable' in extended_attributes:
         property_attributes_list.append('v8::ReadOnly')
     if property_attributes_list:
         property_attributes_list.insert(0, 'v8::DontDelete')
     return property_attributes_list
 
 
-def argument_default_cpp_value(argument):
-    if argument.idl_type.is_dictionary:
+def argument_set_default_value(argument):
+    idl_type = argument.idl_type
+    default_value = argument.default_value
+    if not default_value:
         return None
-    if not argument.default_value:
+    if idl_type.is_dictionary:
+        if not argument.default_value.is_null:
+            raise Exception('invalid default value for dictionary type')
         return None
-    return argument.idl_type.literal_cpp_value(argument.default_value)
+    if idl_type.is_union_type:
+        if argument.default_value.is_null:
+            if not idl_type.includes_nullable_type:
+                raise Exception('invalid default value for union type: null for %s'
+                                % idl_type.name)
+            # Union container objects are "null" initially.
+            return '/* null default value */'
+        if isinstance(default_value.value, basestring):
+            member_type = idl_type.string_member_type
+        elif isinstance(default_value.value, (int, float)):
+            member_type = idl_type.numeric_member_type
+        elif isinstance(default_value.value, bool):
+            member_type = idl_type.boolean_member_type
+        else:
+            member_type = None
+        if member_type is None:
+            raise Exception('invalid default value for union type: %r for %s'
+                            % (default_value.value, idl_type.name))
+        member_type_name = (member_type.inner_type.name
+                            if member_type.is_nullable else
+                            member_type.name)
+        return '%s.set%s(%s)' % (argument.name, member_type_name,
+                                 member_type.literal_cpp_value(default_value))
+    return '%s = %s' % (argument.name,
+                        idl_type.literal_cpp_value(default_value))
 
-IdlArgument.default_cpp_value = property(argument_default_cpp_value)
+IdlArgument.set_default_value = property(argument_set_default_value)
 
 
 def method_returns_promise(method):
     return method.idl_type and method.idl_type.name == 'Promise'
 
 IdlOperation.returns_promise = property(method_returns_promise)
 
 
 def argument_conversion_needs_exception_state(method, argument):
     idl_type = argument.idl_type
     return (idl_type.v8_conversion_needs_exception_state or
             argument.is_variadic or
             (method.returns_promise and (idl_type.is_string_type or
                                          idl_type.is_enum)))