API functions returning Promises should not throw exceptions.

Source/bindings/templates/methods.cpp

 {##############################################################################}
 {% macro generate_method(method, world_suffix) %}
 {% filter conditional(method.conditional_string) %}
 static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     {# Local variables #}
     {% if method.has_exception_state %}
     ExceptionState exceptionState(ExceptionState::ExecutionContext, "{{method.name}}", "{{interface_name}}", info.Holder(), info.GetIsolate());
     {% endif %}
     {# Overloaded methods have length checked during overload resolution #}
@@ skipping 148 matching lines @@
           '"The callback provided as parameter %s is not a function."' %
               (argument.index + 1)) | indent }}
     return;
 }
 {{argument.name}} = {% if argument.is_nullable %}info[{{argument.index}}]->IsNull() ? nullptr : {% endif %}V8{{argument.idl_type}}::create(v8::Handle<v8::Function>::Cast(info[{{argument.index}}]), ScriptState::current(info.GetIsolate()));
 {% endif %}{# argument.is_optional #}
 {% endif %}{# argument.idl_type == 'EventListener' #}
 {% elif argument.is_clamp %}{# argument.is_callback_interface #}
 {# NaN is treated as 0: http://www.w3.org/TR/WebIDL/#es-type-mapping #}
 double {{argument.name}}NativeValue;
+{% if method.idl_type == 'Promise' %}
+TONATIVE_VOID_PROMISE_INTERNAL({{argument.name}}NativeValue, info[{{argument.index}}]->NumberValue(), info);
+{% else %}
 TONATIVE_VOID_INTERNAL({{argument.name}}NativeValue, info[{{argument.index}}]->NumberValue());
+{% endif %}
 if (!std::isnan({{argument.name}}NativeValue))
     {# IDL type is used for clamping, for the right bounds, since different
        IDL integer types have same internal C++ type (int or unsigned) #}
     {{argument.name}} = clampTo<{{argument.idl_type}}>({{argument.name}}NativeValue);
 {% elif argument.idl_type == 'SerializedScriptValue' %}
 {{argument.name}} = SerializedScriptValue::create(info[{{argument.index}}], 0, 0, exceptionState, info.GetIsolate());
 if (exceptionState.hadException()) {
     {{throw_from_exception_state(method)}};
     return;
 }
@@ skipping 131 matching lines @@
 v8SetReturnValueNull(info);
 {% endmacro %}
 
 
 {######################################}
 {% macro throw_type_error(method, error_message) %}
 {% if method.has_exception_state %}
 exceptionState.throwTypeError({{error_message}});
 {{throw_from_exception_state(method)}};
 {% elif method.is_constructor %}
+{% if method.idl_type == 'Promise' %}
+{# FIXME: reduce code duplication between sync / async exception handling. #}
+v8SetReturnValue(info, ScriptPromise::rejectWithTypeError(ScriptState::current(info.GetIsolate()), ExceptionMessages::failedToConstruct("{{interface_name}}", {{error_message}})).v8Value());
+{% else %}
 V8ThrowException::throwTypeError(ExceptionMessages::failedToConstruct("{{interface_name}}", {{error_message}}), info.GetIsolate());
+{% endif %}
 {% else %}{# method.has_exception_state #}
+{% if method.idl_type == 'Promise' %}
+v8SetReturnValue(info, ScriptPromise::rejectWithTypeError(ScriptState::current(info.GetIsolate()), ExceptionMessages::failedToExecute("{{method.name}}", "{{interface_name}}", {{error_message}})).v8Value());
+{% else %}
 V8ThrowException::throwTypeError(ExceptionMessages::failedToExecute("{{method.name}}", "{{interface_name}}", {{error_message}}), info.GetIsolate());
+{% endif %}
 {% endif %}{# method.has_exception_state #}
 {% endmacro %}
 
 
 {######################################}
-{# FIXME: return a rejected Promise if method.idl_type == 'Promise' #}
 {% macro throw_from_exception_state(method) %}
+{% if method.idl_type == 'Promise' %}
+v8SetReturnValue(info, exceptionState.reject(ScriptState::current(info.GetIsolate())).v8Value())
+{%- else %}
 exceptionState.throwIfNeeded()
+{%- endif %}
 {%- endmacro %}
 
 
 {######################################}
 {% macro throw_arity_type_error(method, valid_arities) %}
+{% if method.idl_type == 'Promise' %}
+{% if method.has_exception_state %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeError(ScriptState::current(info.GetIsolate()), exceptionState, {{valid_arities}}, info.Length()).v8Value())
+{%- elif method.is_constructor %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeErrorForConstructor(ScriptState::current(info.GetIsolate()), "{{interface_name}}", {{valid_arities}}, info.Length()).v8Value())
+{%- else %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeErrorForMethod(ScriptState::current(info.GetIsolate()), "{{method.name}}", "{{interface_name}}", {{valid_arities}}, info.Length()).v8Value())
+{%- endif %}
+{%- else %}{# methods.idl_type == 'Promise' #}
 {% if method.has_exception_state %}
 throwArityTypeError(exceptionState, {{valid_arities}}, info.Length())
 {%- elif method.is_constructor %}
 throwArityTypeErrorForConstructor("{{interface_name}}", {{valid_arities}}, info.Length(), info.GetIsolate())
 {%- else %}
 throwArityTypeErrorForMethod("{{method.name}}", "{{interface_name}}", {{valid_arities}}, info.Length(), info.GetIsolate())
 {%- endif %}
+{%- endif %}{# methods.idl_type == 'Promise' #}
 {% endmacro %}
 
 
 {######################################}
 {% macro throw_minimum_arity_type_error(method, number_of_required_arguments) %}
+{% if method.idl_type == 'Promise' %}
+{% if method.has_exception_state %}
+v8SetReturnValue(info, ScriptPromise::rejectWithMinimumArityTypeError(ScriptState::current(info.GetIsolate()), exceptionState, {{number_of_required_arguments}}, info.Length()).v8Value())
+{%- elif method.is_constructor %}
+v8SetReturnValue(info, ScriptPromise::rejectWithMinimumArityTypeErrorForConstructor(ScriptState::current(info.GetIsolate()), "{{interface_name}}", {{number_of_required_arguments}}, info.Length()).v8Value())
+{%- else %}
+v8SetReturnValue(info, ScriptPromise::rejectWithMinimumArityTypeErrorForMethod(ScriptState::current(info.GetIsolate()), "{{method.name}}", "{{interface_name}}", {{number_of_required_arguments}}, info.Length()).v8Value())
+{%- endif %}
+{%- else %}{# methods.idl_type == 'Promise' #}
 {% if method.has_exception_state %}
 throwMinimumArityTypeError(exceptionState, {{number_of_required_arguments}}, info.Length())
 {%- elif method.is_constructor %}
 throwMinimumArityTypeErrorForConstructor("{{interface_name}}", {{number_of_required_arguments}}, info.Length(), info.GetIsolate())
 {%- else %}
 throwMinimumArityTypeErrorForMethod("{{method.name}}", "{{interface_name}}", {{number_of_required_arguments}}, info.Length(), info.GetIsolate())
 {%- endif %}
+{%- endif %}{# methods.idl_type == 'Promise' #}
 {% endmacro %}
 
 
 {##############################################################################}
 {% macro overload_resolution_method(overloads, world_suffix) %}
 static void {{overloads.name}}Method{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     ExceptionState exceptionState(ExceptionState::ExecutionContext, "{{overloads.name}}", "{{interface_name}}", info.Holder(), info.GetIsolate());
     {% if overloads.measure_all_as %}
     UseCounter::count(callingExecutionContext(info.GetIsolate()), UseCounter::{{overloads.measure_all_as}});
@@ skipping 226 matching lines @@
 v8::Handle<v8::Object> wrapper = wrap(impl.get(), info.Holder(), info.GetIsolate());
 {% else %}
 {% set constructor_class = v8_class + ('Constructor'
                                        if constructor.is_named_constructor else
                                        '') %}
 v8::Handle<v8::Object> wrapper = info.Holder();
 V8DOMWrapper::associateObjectWithWrapper<{{v8_class}}>(impl.release(), &{{constructor_class}}::wrapperTypeInfo, wrapper, info.GetIsolate(), {{wrapper_configuration}});
 {% endif %}
 v8SetReturnValue(info, wrapper);
 {% endmacro %}