API functions returning Promises should not throw exceptions.

Source/bindings/templates/methods.cpp

Index: Source/bindings/templates/methods.cpp
diff --git a/Source/bindings/templates/methods.cpp b/Source/bindings/templates/methods.cpp
index 95ab1b1a27ee7e229e6b58dbe1bd64f7545a2bd4..171fbbe2b4785a775a217111fe6cb66e66fb552f 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -24,7 +24,7 @@ static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const
     {% if interface_name == 'EventTarget' %}
     if (DOMWindow* window = impl->toDOMWindow()) {
         if (!BindingSecurity::shouldAllowAccessToFrame(info.GetIsolate(), window->frame(), exceptionState)) {
-            exceptionState.throwIfNeeded();
+            {{throw_from_exception_state(method)}};
             return;
         }
         if (!window->document())
@@ -32,14 +32,14 @@ static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const
     }
     {% elif method.is_check_security_for_frame %}
     if (!BindingSecurity::shouldAllowAccessToFrame(info.GetIsolate(), impl->frame(), exceptionState)) {
-        exceptionState.throwIfNeeded();
+        {{throw_from_exception_state(method)}};
         return;
     }
     {% endif %}
     {% if method.is_check_security_for_node %}
     if (!BindingSecurity::shouldAllowAccessToNode(info.GetIsolate(), impl->{{method.name}}(exceptionState), exceptionState)) {
         v8SetReturnValueNull(info);
-        exceptionState.throwIfNeeded();
+        {{throw_from_exception_state(method)}};
         return;
     }
     {% endif %}
@@ -134,15 +134,21 @@ OwnPtr<{{argument.idl_type}}> {{argument.name}} = {% if argument.is_nullable %}i
 {% elif argument.is_clamp %}{# argument.is_callback_interface #}
 {# NaN is treated as 0: http://www.w3.org/TR/WebIDL/#es-type-mapping #}
 {{argument.cpp_type}} {{argument.name}} = 0;
+{% if method.idl_type == 'Promise' %}
+TONATIVE_VOID_ASYNC(double, {{argument.name}}NativeValue, info[{{argument.index}}]->NumberValue(), info);
+{% else %}
 TONATIVE_VOID(double, {{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.cpp_type}} {{argument.name}} = SerializedScriptValue::create(info[{{argument.index}}], 0, 0, exceptionState, info.GetIsolate());
-if (exceptionState.throwIfNeeded())
+if (exceptionState.hadException()) {
+    {{throw_from_exception_state(method)}};
     return;
+}
 {% elif argument.is_variadic_wrapper_type %}
 {{argument.vector_type}}<{{argument.cpp_type}} > {{argument.name}};
 for (int i = {{argument.index}}; i < info.Length(); ++i) {
@@ -153,9 +159,13 @@ for (int i = {{argument.index}}; i < info.Length(); ++i) {
     }
     {{argument.name}}.append(V8{{argument.idl_type}}::toNative(v8::Handle<v8::Object>::Cast(info[i])));
 }
+{% else %}{# argument.is_nullable #}
+{% if method.idl_type == 'Promise' %}
+{{argument.v8_value_to_local_cpp_value_async}};
 {% else %}
 {{argument.v8_value_to_local_cpp_value}};
 {% endif %}
+{% endif %}{# argument.is_nullable #}
 {% if argument.enum_validation_expression %}
 {# Methods throw on invalid enum values: http://www.w3.org/TR/WebIDL/#idl-enums #}
 String string = {{argument.name}};
@@ -208,8 +218,10 @@ RefPtr<ScriptArguments> scriptArguments(createScriptArguments(info, {{method.num
 {% endif %}
 {# Post-call #}
 {% if method.is_raises_exception %}
-if (exceptionState.throwIfNeeded())
+if (exceptionState.hadException()) {
+    {{throw_from_exception_state(method)}};
     return;
+}
 {% endif %}
 {# Set return value #}
 {% if method.is_constructor %}
@@ -245,17 +257,44 @@ v8SetReturnValueNull(info);
 {% macro throw_type_error(method, error_message) %}
 {% if method.has_exception_state %}
 exceptionState.throwTypeError({{error_message}});
-exceptionState.throwIfNeeded();
+{{throw_from_exception_state(method)}};
 {%- elif method.is_constructor %}
+{% if method.idl_type == 'Promise' %}
+v8SetReturnValue(info, ScriptPromise::rejectWithTypeError(ExceptionMessages::failedToConstruct("{{interface_name}}", {{error_message}}), info.GetIsolate()).v8Value());
+{%- else %}
 throwTypeError(ExceptionMessages::failedToConstruct("{{interface_name}}", {{error_message}}), info.GetIsolate());
+{%- endif %}
+{%- else %}{# method.has_exception_state #}
+{% if method.idl_type == 'Promise' %}
+v8SetReturnValue(info, ScriptPromise::rejectWithTypeError(ExceptionMessages::failedToExecute("{{method.name}}", "{{interface_name}}", {{error_message}}), info.GetIsolate()).v8Value());
 {%- else %}
 throwTypeError(ExceptionMessages::failedToExecute("{{method.name}}", "{{interface_name}}", {{error_message}}), info.GetIsolate());
 {%- endif %}
+{%- endif %}{# method.has_exception_state #}
+{% endmacro %}
+
+
+{######################################}
+{% macro throw_from_exception_state(method) %}
+{% if method.idl_type == 'Promise' %}
+v8SetReturnValue(info, exceptionState.reject().v8Value())
+{%- else %}
+exceptionState.throwIfNeeded()
+{%- endif %}
 {% endmacro %}
 
 
 {######################################}
 {% macro throw_arity_type_error(method, number_of_required_arguments) %}
+{% if method.idl_type == 'Promise' %}
+{% if method.has_exception_state %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeError(exceptionState, {{number_of_required_arguments}}, info.Length()).v8Value())
+{%- elif method.is_constructor %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeErrorForConstructor("{{interface_name}}", {{number_of_required_arguments}}, info.Length(), info.GetIsolate().v8Value())
+{%- else %}
+v8SetReturnValue(info, ScriptPromise::rejectWithArityTypeErrorForMethod("{{method.name}}", "{{interface_name}}", {{number_of_required_arguments}}, info.Length(), info.GetIsolate()).v8Value())
+{%- endif %}
+{%- else %}{# methods.idl_type == 'Promise' #}
 {% if method.has_exception_state %}
 throwArityTypeError(exceptionState, {{number_of_required_arguments}}, info.Length())
 {%- elif method.is_constructor %}
@@ -263,6 +302,7 @@ throwArityTypeErrorForConstructor("{{interface_name}}", {{number_of_required_arg
 {%- else %}
 throwArityTypeErrorForMethod("{{method.name}}", "{{interface_name}}", {{number_of_required_arguments}}, info.Length(), info.GetIsolate())
 {%- endif %}
+{%- endif %}{# methods.idl_type == 'Promise' #}
 {% endmacro %}