third_party/WebKit/Source/bindings/templates/callback_function.cpp.tmpl

{% from 'utilities.cpp.tmpl' import declare_enum_validation_variable, v8_value_to_local_cpp_value %}
{% filter format_blink_cpp_source_code %}

{% include 'copyright_block.txt' %}

#include "{{this_include_header_name}}.h"

{% for filename in cpp_includes %}
#include "{{filename}}"
{% endfor %}

namespace blink {

v8::Maybe<{{return_cpp_type}}> {{cpp_class}}::Invoke({{argument_declarations | join(', ')}}) {
  // This function implements "invoke" steps in
  // "3.10. Invoking callback functions".
  // https://heycam.github.io/webidl/#es-invoking-callback-functions

  {# TODO(yukishiino): This implementation does not support a return type of
     promise type, in which case this function needs to convert any exception
     into a rejected promise. See also step 14.4. to 14.6. #}

  if (!IsCallbackFunctionRunnable(CallbackRelevantScriptState())) {
    // Wrapper-tracing for the callback function makes the function object and
    // its creation context alive. Thus it's safe to use the creation context
    // of the callback function here.
    v8::HandleScope handle_scope(GetIsolate());
    CHECK(!CallbackFunction().IsEmpty());
    v8::Context::Scope context_scope(CallbackFunction()->CreationContext());
    V8ThrowException::ThrowError(
        GetIsolate(),
        ExceptionMessages::FailedToExecute(
            "invoke",
            "{{callback_function_name}}",
            "The provided callback is no longer runnable."));
    return v8::Nothing<{{return_cpp_type}}>();
  }

  // step 4. If ! IsCallable(F) is false:
  //
  // As Blink no longer supports [TreatNonObjectAsNull], there must be no such a
  // case.
#if DCHECK_IS_ON()
  {
    v8::HandleScope handle_scope(GetIsolate());
    DCHECK(CallbackFunction()->IsFunction());
  }
#endif

  // step 8. Prepare to run script with relevant settings.
  ScriptState::Scope callback_relevant_context_scope(
      CallbackRelevantScriptState());
  // step 9. Prepare to run a callback with stored settings.
  {# TODO(yukishiino): Callback function type value must make the incumbent
     environment alive, i.e. the reference to v8::Context must be strong. #}
  if (IncumbentScriptState()->GetContext().IsEmpty()) {
    V8ThrowException::ThrowError(
        GetIsolate(),
        ExceptionMessages::FailedToExecute(
            "invoke",
            "{{callback_function_name}}",
            "The provided callback is no longer runnable."));
    return v8::Nothing<{{return_cpp_type}}>();
  }
  v8::Context::BackupIncumbentScope backup_incumbent_scope(
      IncumbentScriptState()->GetContext());

  v8::Local<v8::Value> this_arg = ToV8(callback_this_value,
                                       CallbackRelevantScriptState());

  {% for argument in arguments if argument.enum_values %}
  // Enum values provided by Blink must be valid, otherwise typo.
#if DCHECK_IS_ON()
  {
    {% set valid_enum_variables = 'valid_' + argument.name + '_values' %}
    {{declare_enum_validation_variable(argument.enum_values, valid_enum_variables) | indent(4)}}
    ExceptionState exception_state(GetIsolate(),
                                   ExceptionState::kExecutionContext,
                                   "{{callback_function_name}}",
                                   "invoke");
    if (!IsValidEnum({{argument.name}}, {{valid_enum_variables}}, WTF_ARRAY_LENGTH({{valid_enum_variables}}), "{{argument.enum_type}}", exception_state)) {
      NOTREACHED();
      return v8::Nothing<{{return_cpp_type}}>();
    }
  }
#endif

  {% endfor %}

  // step 10. Let esArgs be the result of converting args to an ECMAScript
  //   arguments list. If this throws an exception, set completion to the
  //   completion value representing the thrown exception and jump to the step
  //   labeled return.
  v8::Local<v8::Object> argument_creation_context =
      CallbackRelevantScriptState()->GetContext()->Global();
  ALLOW_UNUSED_LOCAL(argument_creation_context);
  {% for argument in arguments %}
  v8::Local<v8::Value> {{argument.v8_name}} = {{argument.cpp_value_to_v8_value}};
  {% endfor %}
  {% if arguments %}
  v8::Local<v8::Value> argv[] = { {{arguments | join(', ', 'v8_name')}} };
  {% else %}
  {# Zero-length arrays are ill-formed in C++. #}
  v8::Local<v8::Value> *argv = nullptr;
  {% endif %}

  // step 11. Let callResult be Call(X, thisArg, esArgs).
  v8::Local<v8::Value> call_result;
  if (!V8ScriptRunner::CallFunction(
          CallbackFunction(),
          ExecutionContext::From(CallbackRelevantScriptState()),
          this_arg,
          {{arguments | length}},
          argv,
          GetIsolate()).ToLocal(&call_result)) {
    // step 12. If callResult is an abrupt completion, set completion to
    //   callResult and jump to the step labeled return.
    return v8::Nothing<{{return_cpp_type}}>();
  }

  // step 13. Set completion to the result of converting callResult.[[Value]] to
  //   an IDL value of the same type as the operation's return type.
  {% if idl_type == 'void' %}
  return v8::JustVoid();
  {% else %}
  {
    ExceptionState exceptionState(GetIsolate(),
                                  ExceptionState::kExecutionContext,
                                  "{{callback_function_name}}",
                                  "invoke");
    {{v8_value_to_local_cpp_value(return_value_conversion) | indent(4)}}
    return v8::Just<{{return_cpp_type}}>(native_result);
  }
  {% endif %}
}

{% if idl_type == 'void' %}
void {{cpp_class}}::InvokeAndReportException({{argument_declarations | join(', ')}}) {
  v8::TryCatch try_catch(GetIsolate());
  try_catch.SetVerbose(true);

  v8::Maybe<void> maybe_result =
      Invoke({{
                 (['callback_this_value'] +
                  (arguments|map(attribute='name')|list)
                 )|join(', ')
             }});
  // An exception if any is killed with the v8::TryCatch above.
  ALLOW_UNUSED_LOCAL(maybe_result);
}
{% endif %}

}  // namespace blink

{% endfilter %}{# format_blink_cpp_source_code #}