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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at */
* A struct that encapsulates a JSContex and information about
* which binding method was called. The idea is to automatically annotate
* exceptions thrown via the BindingCallContext with the method name.
#ifndef mozilla_dom_BindingCallContext_h
#define mozilla_dom_BindingCallContext_h
#include <utility>
#include "js/TypeDecls.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/ErrorResult.h"
namespace mozilla {
namespace dom {
// aCx is allowed to be null. If it is, the BindingCallContext should
// generally act like a null JSContext*: test false when tested as a boolean
// and produce nullptr when used as a JSContext*.
// aMethodDescription should be something with longer lifetime than this
// BindingCallContext. Most simply, a string literal. nullptr or "" is
// allowed if we want to not have any particular message description. This
// argument corresponds to the "context" string used for DOM error codes that
// support one. See Errors.msg and the documentation for
// ErrorResult::MaybeSetPendingException for details on he context arg.
BindingCallContext(JSContext* aCx, const char* aMethodDescription)
: mCx(aCx), mDescription(aMethodDescription) {}
~BindingCallContext() = default;
// Allow passing a BindingCallContext as a JSContext*, as needed.
operator JSContext*() const { return mCx; }
// Allow testing a BindingCallContext for falsiness, just like a
// JSContext* could be tested.
explicit operator bool() const { return !!mCx; }
// Allow throwing an error message, if it has a context.
template <dom::ErrNum errorNumber, typename... Ts>
bool ThrowErrorMessage(Ts&&... aMessageArgs) const {
"We plan to add a context; it better be expected!");
return dom::ThrowErrorMessage<errorNumber>(
mCx, mDescription, std::forward<Ts>(aMessageArgs)...);
JSContext* const mCx;
const char* const mDescription;
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_BindingCallContext_h