API functions returning Promises should not throw exceptions.

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 155 matching lines @@
         'is_nullable': idl_type.is_nullable,
         'is_optional': argument.is_optional,
         'is_strict_type_checking': 'StrictTypeChecking' in extended_attributes,
         'is_variadic_wrapper_type': is_variadic_wrapper_type,
         'vector_type': v8_types.cpp_ptr_type('Vector', 'HeapVector', idl_type.gc_type),
         'is_wrapper_type': idl_type.is_wrapper_type,
         'name': argument.name,
         'v8_set_return_value_for_main_world': v8_set_return_value(interface.name, method, this_cpp_value, for_main_world=True),
         'v8_set_return_value': v8_set_return_value(interface.name, method, this_cpp_value),
         'v8_value_to_local_cpp_value': v8_value_to_local_cpp_value(argument, index),
+        'v8_value_to_local_cpp_value_async': v8_value_to_local_cpp_value_async(argument, index),
     }
 
 
 ################################################################################
 # Value handling
 ################################################################################
 
 def cpp_value(interface, method, number_of_arguments):
     def cpp_argument(argument):
         idl_type = argument.idl_type
@@ skipping 69 matching lines @@
     # [Default=NullString]
     if (argument.is_optional and idl_type.name == 'String' and
         extended_attributes.get('Default') == 'NullString'):
         v8_value = 'argumentOrNull(info, %s)' % index
     else:
         v8_value = 'info[%s]' % index
     return idl_type.v8_value_to_local_cpp_value(extended_attributes, v8_value,
                                                 name, index=index)
 
 
+def v8_value_to_local_cpp_value_async(argument, index):

[Nils Barth (inactive), 2014/04/11 10:26:39]

Could you merge this with above, only adding an async=False argument?
The only difference is the macro name in the variadic case, right?
So for the variadic case you can put:
macro = 'TONATIVE_VOID_ASYNC' if async else 'TONATIVE_VOID'
and then have the return expression be something like:
        return '{macro}({vector_type}<{cpp_type}>, {name},
toNativeArguments<{cpp_type}>(info, {index}), info)'.format(
            macro=macro, vector_type=vector_type, cpp_type=idl_type.cpp_type,
            name=name, index=index)

[yhirano, 2014/04/11 10:54:22]

Done. I split the variadic case to another function.

+    extended_attributes = argument.extended_attributes
+    idl_type = argument.idl_type
+    name = argument.name
+    if argument.is_variadic:
+        vector_type = v8_types.cpp_ptr_type('Vector', 'HeapVector', idl_type.gc_type)
+        return 'TONATIVE_VOID_ASYNC({vector_type}<{cpp_type}>, {name}, toNativeArguments<{cpp_type}>(info, {index}), info)'.format(
+            vector_type=vector_type, cpp_type=idl_type.cpp_type, name=name,
+            index=index)
+    # [Default=NullString]
+    if (argument.is_optional and idl_type.name == 'String' and
+        extended_attributes.get('Default') == 'NullString'):
+        v8_value = 'argumentOrNull(info, %s)' % index
+    else:
+        v8_value = 'info[%s]' % index
+    return idl_type.v8_value_to_local_cpp_value(extended_attributes, v8_value,
+                                                name, index=index, async=True)
+
+
 ################################################################################
 # Auxiliary functions
 ################################################################################
 
 # [NotEnumerable]
 def property_attributes(method):
     extended_attributes = method.extended_attributes
     property_attributes_list = []
     if 'NotEnumerable' in extended_attributes:
         property_attributes_list.append('v8::DontEnum')
     if 'ReadOnly' 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 union_arguments(idl_type):
     """Return list of ['result0Enabled', 'result0', 'result1Enabled', ...] for union types, for use in setting return value"""
     return [arg
             for i in range(len(idl_type.member_types))
             for arg in ['result%sEnabled' % i, 'result%s' % i]]
 
 IdlType.union_arguments = property(lambda self: None)
 IdlUnionType.union_arguments = property(union_arguments)