mirror of
https://github.com/classilla/tenfourfox.git
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972 lines
33 KiB
JavaScript
972 lines
33 KiB
JavaScript
/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
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/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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/**
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* This implementation file is imported by the Promise.jsm module, and as a
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* special case by the debugger server. To support chrome debugging, the
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* debugger server needs to have all its code in one global, so it must use
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* loadSubScript directly.
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*
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* In the general case, this script should be used by importing Promise.jsm:
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*
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* Components.utils.import("resource://gre/modules/Promise.jsm");
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*
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* More documentation can be found in the Promise.jsm module.
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*/
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////////////////////////////////////////////////////////////////////////////////
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//// Globals
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// Obtain an instance of Cu. How this instance is obtained depends on how this
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// file is loaded.
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//
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// This file can be loaded in three different ways:
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// 1. As a CommonJS module, by Loader.jsm, on the main thread.
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// 2. As a CommonJS module, by worker-loader.js, on a worker thread.
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// 3. As a subscript, by Promise.jsm, on the main thread.
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//
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// If require is defined, the file is loaded as a CommonJS module. Components
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// will not be defined in that case, but we can obtain an instance of Cu from
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// the chrome module. Otherwise, this file is loaded as a subscript, and we can
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// obtain an instance of Cu from Components directly.
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//
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// If the file is loaded as a CommonJS module on a worker thread, the instance
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// of Cu obtained from the chrome module will be null. The reason for this is
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// that Components is not defined in worker threads, so no instance of Cu can
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// be obtained.
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var Cu = this.require ? require("chrome").Cu : Components.utils;
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var Cc = this.require ? require("chrome").Cc : Components.classes;
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var Ci = this.require ? require("chrome").Ci : Components.interfaces;
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// If we can access Components, then we use it to capture an async
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// parent stack trace; see scheduleWalkerLoop. However, as it might
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// not be available (see above), users of this must check it first.
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var Components_ = this.require ? require("chrome").components : Components;
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// If Cu is defined, use it to lazily define the FinalizationWitnessService.
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if (Cu) {
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Cu.import("resource://gre/modules/Services.jsm");
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Cu.import("resource://gre/modules/XPCOMUtils.jsm");
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XPCOMUtils.defineLazyServiceGetter(this, "FinalizationWitnessService",
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"@mozilla.org/toolkit/finalizationwitness;1",
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"nsIFinalizationWitnessService");
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}
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const STATUS_PENDING = 0;
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const STATUS_RESOLVED = 1;
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const STATUS_REJECTED = 2;
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// This N_INTERNALS name allow internal properties of the Promise to be
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// accessed only by this module, while still being visible on the object
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// manually when using a debugger. This doesn't strictly guarantee that the
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// properties are inaccessible by other code, but provide enough protection to
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// avoid using them by mistake.
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const salt = Math.floor(Math.random() * 100);
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const N_INTERNALS = "{private:internals:" + salt + "}";
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// We use DOM Promise for scheduling the walker loop.
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const DOMPromise = Cu ? Promise : null;
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/////// Warn-upon-finalization mechanism
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//
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// One of the difficult problems with promises is locating uncaught
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// rejections. We adopt the following strategy: if a promise is rejected
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// at the time of its garbage-collection *and* if the promise is at the
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// end of a promise chain (i.e. |thatPromise.then| has never been
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// called), then we print a warning.
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//
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// let deferred = Promise.defer();
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// let p = deferred.promise.then();
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// deferred.reject(new Error("I am un uncaught error"));
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// deferred = null;
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// p = null;
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//
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// In this snippet, since |deferred.promise| is not the last in the
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// chain, no error will be reported for that promise. However, since
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// |p| is the last promise in the chain, the error will be reported
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// for |p|.
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//
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// Note that this may, in some cases, cause an error to be reported more
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// than once. For instance, consider:
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//
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// let deferred = Promise.defer();
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// let p1 = deferred.promise.then();
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// let p2 = deferred.promise.then();
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// deferred.reject(new Error("I am an uncaught error"));
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// p1 = p2 = deferred = null;
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//
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// In this snippet, the error is reported both by p1 and by p2.
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//
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var PendingErrors = {
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// An internal counter, used to generate unique id.
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_counter: 0,
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// Functions registered to be notified when a pending error
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// is reported as uncaught.
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_observers: new Set(),
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_map: new Map(),
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/**
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* Initialize PendingErrors
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*/
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init: function() {
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Services.obs.addObserver(function observe(aSubject, aTopic, aValue) {
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PendingErrors.report(aValue);
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}, "promise-finalization-witness", false);
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},
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/**
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* Register an error as tracked.
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*
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* @return The unique identifier of the error.
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*/
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register: function(error) {
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let id = "pending-error-" + (this._counter++);
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//
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// At this stage, ideally, we would like to store the error itself
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// and delay any treatment until we are certain that we will need
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// to report that error. However, in the (unlikely but possible)
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// case the error holds a reference to the promise itself, doing so
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// would prevent the promise from being garbabe-collected, which
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// would both cause a memory leak and ensure that we cannot report
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// the uncaught error.
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//
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// To avoid this situation, we rather extract relevant data from
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// the error and further normalize it to strings.
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//
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let value = {
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date: new Date(),
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message: "" + error,
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fileName: null,
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stack: null,
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lineNumber: null
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};
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try { // Defend against non-enumerable values
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if (error && error instanceof Ci.nsIException) {
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// nsIException does things a little differently.
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try {
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// For starters |.toString()| does not only contain the message, but
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// also the top stack frame, and we don't really want that.
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value.message = error.message;
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} catch (ex) {
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// Ignore field
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}
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try {
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// All lowercase filename. ;)
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value.fileName = error.filename;
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} catch (ex) {
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// Ignore field
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}
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try {
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value.lineNumber = error.lineNumber;
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} catch (ex) {
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// Ignore field
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}
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} else if (typeof error == "object" && error) {
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for (let k of ["fileName", "stack", "lineNumber"]) {
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try { // Defend against fallible getters and string conversions
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let v = error[k];
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value[k] = v ? ("" + v) : null;
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} catch (ex) {
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// Ignore field
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}
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}
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}
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if (!value.stack) {
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// |error| is not an Error (or Error-alike). Try to figure out the stack.
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let stack = null;
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if (error && error.location &&
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error.location instanceof Ci.nsIStackFrame) {
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// nsIException has full stack frames in the |.location| member.
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stack = error.location;
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} else {
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// Components.stack to the rescue!
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stack = Components.stack;
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// Remove those top frames that refer to Promise.jsm.
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while (stack) {
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if (!stack.filename.endsWith("/Promise.jsm")) {
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break;
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}
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stack = stack.caller;
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}
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}
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if (stack) {
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let frames = [];
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while (stack) {
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frames.push(stack);
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stack = stack.caller;
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}
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value.stack = frames.join("\n");
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}
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}
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} catch (ex) {
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// Ignore value
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}
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this._map.set(id, value);
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return id;
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},
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/**
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* Notify all observers that a pending error is now uncaught.
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*
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* @param id The identifier of the pending error, as returned by
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* |register|.
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*/
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report: function(id) {
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let value = this._map.get(id);
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if (!value) {
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return; // The error has already been reported
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}
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this._map.delete(id);
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for (let obs of this._observers.values()) {
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obs(value);
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}
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},
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/**
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* Mark all pending errors are uncaught, notify the observers.
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*/
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flush: function() {
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// Since we are going to modify the map while walking it,
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// let's copying the keys first.
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for (let key of Array.from(this._map.keys())) {
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this.report(key);
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}
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},
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/**
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* Stop tracking an error, as this error has been caught,
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* eventually.
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*/
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unregister: function(id) {
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this._map.delete(id);
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},
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/**
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* Add an observer notified when an error is reported as uncaught.
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*
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* @param {function} observer A function notified when an error is
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* reported as uncaught. Its arguments are
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* {message, date, fileName, stack, lineNumber}
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* All arguments are optional.
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*/
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addObserver: function(observer) {
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this._observers.add(observer);
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},
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/**
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* Remove an observer added with addObserver
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*/
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removeObserver: function(observer) {
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this._observers.delete(observer);
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},
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/**
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* Remove all the observers added with addObserver
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*/
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removeAllObservers: function() {
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this._observers.clear();
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}
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};
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// Initialize the warn-upon-finalization mechanism if and only if Cu is defined.
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// Otherwise, FinalizationWitnessService won't be defined (see above).
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if (Cu) {
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PendingErrors.init();
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}
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// Default mechanism for displaying errors
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PendingErrors.addObserver(function(details) {
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const generalDescription = "A promise chain failed to handle a rejection." +
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" Did you forget to '.catch', or did you forget to 'return'?\nSee" +
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" https://developer.mozilla.org/Mozilla/JavaScript_code_modules/Promise.jsm/Promise\n\n";
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let error = Cc['@mozilla.org/scripterror;1'].createInstance(Ci.nsIScriptError);
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if (!error || !Services.console) {
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// Too late during shutdown to use the nsIConsole
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dump("*************************\n");
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dump(generalDescription);
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dump("On: " + details.date + "\n");
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dump("Full message: " + details.message + "\n");
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dump("Full stack: " + (details.stack||"not available") + "\n");
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dump("*************************\n");
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return;
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}
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let message = details.message;
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if (details.stack) {
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message += "\nFull Stack: " + details.stack;
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}
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error.init(
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/*message*/ generalDescription +
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"Date: " + details.date + "\nFull Message: " + message,
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/*sourceName*/ details.fileName,
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/*sourceLine*/ details.lineNumber?("" + details.lineNumber):0,
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/*lineNumber*/ details.lineNumber || 0,
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/*columnNumber*/ 0,
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/*flags*/ Ci.nsIScriptError.errorFlag,
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/*category*/ "chrome javascript");
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Services.console.logMessage(error);
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});
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///////// Additional warnings for developers
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//
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// The following error types are considered programmer errors, which should be
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// reported (possibly redundantly) so as to let programmers fix their code.
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const ERRORS_TO_REPORT = ["EvalError", "RangeError", "ReferenceError", "TypeError"];
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////////////////////////////////////////////////////////////////////////////////
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//// Promise
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/**
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* The Promise constructor. Creates a new promise given an executor callback.
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* The executor callback is called with the resolve and reject handlers.
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*
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* @param aExecutor
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* The callback that will be called with resolve and reject.
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*/
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this.Promise = function Promise(aExecutor)
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{
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if (typeof(aExecutor) != "function") {
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throw new TypeError("Promise constructor must be called with an executor.");
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}
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/*
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* Object holding all of our internal values we associate with the promise.
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*/
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Object.defineProperty(this, N_INTERNALS, { value: {
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/*
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* Internal status of the promise. This can be equal to STATUS_PENDING,
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* STATUS_RESOLVED, or STATUS_REJECTED.
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*/
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status: STATUS_PENDING,
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/*
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* When the status property is STATUS_RESOLVED, this contains the final
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* resolution value, that cannot be a promise, because resolving with a
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* promise will cause its state to be eventually propagated instead. When the
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* status property is STATUS_REJECTED, this contains the final rejection
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* reason, that could be a promise, even if this is uncommon.
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*/
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value: undefined,
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/*
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* Array of Handler objects registered by the "then" method, and not processed
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* yet. Handlers are removed when the promise is resolved or rejected.
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*/
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handlers: [],
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/**
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* When the status property is STATUS_REJECTED and until there is
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* a rejection callback, this contains an array
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* - {string} id An id for use with |PendingErrors|;
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* - {FinalizationWitness} witness A witness broadcasting |id| on
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* notification "promise-finalization-witness".
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*/
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witness: undefined
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}});
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Object.seal(this);
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let resolve = PromiseWalker.completePromise
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.bind(PromiseWalker, this, STATUS_RESOLVED);
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let reject = PromiseWalker.completePromise
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.bind(PromiseWalker, this, STATUS_REJECTED);
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try {
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aExecutor.call(undefined, resolve, reject);
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} catch (ex) {
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reject(ex);
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}
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}
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/**
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* Calls one of the provided functions as soon as this promise is either
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* resolved or rejected. A new promise is returned, whose state evolves
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* depending on this promise and the provided callback functions.
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*
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* The appropriate callback is always invoked after this method returns, even
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* if this promise is already resolved or rejected. You can also call the
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* "then" method multiple times on the same promise, and the callbacks will be
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* invoked in the same order as they were registered.
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*
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* @param aOnResolve
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* If the promise is resolved, this function is invoked with the
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* resolution value of the promise as its only argument, and the
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* outcome of the function determines the state of the new promise
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* returned by the "then" method. In case this parameter is not a
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* function (usually "null"), the new promise returned by the "then"
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* method is resolved with the same value as the original promise.
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*
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* @param aOnReject
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* If the promise is rejected, this function is invoked with the
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* rejection reason of the promise as its only argument, and the
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* outcome of the function determines the state of the new promise
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* returned by the "then" method. In case this parameter is not a
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* function (usually left "undefined"), the new promise returned by the
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* "then" method is rejected with the same reason as the original
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* promise.
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*
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* @return A new promise that is initially pending, then assumes a state that
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* depends on the outcome of the invoked callback function:
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* - If the callback returns a value that is not a promise, including
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* "undefined", the new promise is resolved with this resolution
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* value, even if the original promise was rejected.
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* - If the callback throws an exception, the new promise is rejected
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* with the exception as the rejection reason, even if the original
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* promise was resolved.
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* - If the callback returns a promise, the new promise will
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* eventually assume the same state as the returned promise.
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*
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* @note If the aOnResolve callback throws an exception, the aOnReject
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* callback is not invoked. You can register a rejection callback on
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* the returned promise instead, to process any exception occurred in
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* either of the callbacks registered on this promise.
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*/
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Promise.prototype.then = function (aOnResolve, aOnReject)
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{
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let handler = new Handler(this, aOnResolve, aOnReject);
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this[N_INTERNALS].handlers.push(handler);
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|
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// Ensure the handler is scheduled for processing if this promise is already
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// resolved or rejected.
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if (this[N_INTERNALS].status != STATUS_PENDING) {
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// This promise is not the last in the chain anymore. Remove any watchdog.
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if (this[N_INTERNALS].witness != null) {
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let [id, witness] = this[N_INTERNALS].witness;
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this[N_INTERNALS].witness = null;
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witness.forget();
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PendingErrors.unregister(id);
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}
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PromiseWalker.schedulePromise(this);
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}
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return handler.nextPromise;
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};
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|
|
/**
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|
* Invokes `promise.then` with undefined for the resolve handler and a given
|
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* reject handler.
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*
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* @param aOnReject
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* The rejection handler.
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|
*
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* @return A new pending promise returned.
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|
*
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* @see Promise.prototype.then
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|
*/
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Promise.prototype.catch = function (aOnReject)
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{
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return this.then(undefined, aOnReject);
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|
};
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|
|
|
/**
|
|
* Creates a new pending promise and provides methods to resolve or reject it.
|
|
*
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|
* @return A new object, containing the new promise in the "promise" property,
|
|
* and the methods to change its state in the "resolve" and "reject"
|
|
* properties. See the Deferred documentation for details.
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|
*/
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|
Promise.defer = function ()
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{
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return new Deferred();
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|
};
|
|
|
|
/**
|
|
* Creates a new promise resolved with the specified value, or propagates the
|
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* state of an existing promise.
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|
*
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* @param aValue
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* If this value is not a promise, including "undefined", it becomes
|
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* the resolution value of the returned promise. If this value is a
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* promise, then the returned promise will eventually assume the same
|
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* state as the provided promise.
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*
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* @return A promise that can be pending, resolved, or rejected.
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|
*/
|
|
Promise.resolve = function (aValue)
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|
{
|
|
if (aValue && typeof(aValue) == "function" && aValue.isAsyncFunction) {
|
|
throw new TypeError(
|
|
"Cannot resolve a promise with an async function. " +
|
|
"You should either invoke the async function first " +
|
|
"or use 'Task.spawn' instead of 'Task.async' to start " +
|
|
"the Task and return its promise.");
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}
|
|
|
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if (aValue instanceof Promise) {
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|
return aValue;
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}
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return new Promise((aResolve) => aResolve(aValue));
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|
};
|
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|
|
/**
|
|
* Creates a new promise rejected with the specified reason.
|
|
*
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|
* @param aReason
|
|
* The rejection reason for the returned promise. Although the reason
|
|
* can be "undefined", it is generally an Error object, like in
|
|
* exception handling.
|
|
*
|
|
* @return A rejected promise.
|
|
*
|
|
* @note The aReason argument should not be a promise. Using a rejected
|
|
* promise for the value of aReason would make the rejection reason
|
|
* equal to the rejected promise itself, and not its rejection reason.
|
|
*/
|
|
Promise.reject = function (aReason)
|
|
{
|
|
return new Promise((_, aReject) => aReject(aReason));
|
|
};
|
|
|
|
/**
|
|
* Returns a promise that is resolved or rejected when all values are
|
|
* resolved or any is rejected.
|
|
*
|
|
* @param aValues
|
|
* Iterable of promises that may be pending, resolved, or rejected. When
|
|
* all are resolved or any is rejected, the returned promise will be
|
|
* resolved or rejected as well.
|
|
*
|
|
* @return A new promise that is fulfilled when all values are resolved or
|
|
* that is rejected when any of the values are rejected. Its
|
|
* resolution value will be an array of all resolved values in the
|
|
* given order, or undefined if aValues is an empty array. The reject
|
|
* reason will be forwarded from the first promise in the list of
|
|
* given promises to be rejected.
|
|
*/
|
|
Promise.all = function (aValues)
|
|
{
|
|
if (aValues == null || typeof(aValues[Symbol.iterator]) != "function") {
|
|
throw new Error("Promise.all() expects an iterable.");
|
|
}
|
|
|
|
return new Promise((resolve, reject) => {
|
|
let values = Array.isArray(aValues) ? aValues : [...aValues];
|
|
let countdown = values.length;
|
|
let resolutionValues = new Array(countdown);
|
|
|
|
if (!countdown) {
|
|
resolve(resolutionValues);
|
|
return;
|
|
}
|
|
|
|
function checkForCompletion(aValue, aIndex) {
|
|
resolutionValues[aIndex] = aValue;
|
|
if (--countdown === 0) {
|
|
resolve(resolutionValues);
|
|
}
|
|
}
|
|
|
|
for (let i = 0; i < values.length; i++) {
|
|
let index = i;
|
|
let value = values[i];
|
|
let resolver = val => checkForCompletion(val, index);
|
|
|
|
if (value && typeof(value.then) == "function") {
|
|
value.then(resolver, reject);
|
|
} else {
|
|
// Given value is not a promise, forward it as a resolution value.
|
|
resolver(value);
|
|
}
|
|
}
|
|
});
|
|
};
|
|
|
|
/**
|
|
* Returns a promise that is resolved or rejected when the first value is
|
|
* resolved or rejected, taking on the value or reason of that promise.
|
|
*
|
|
* @param aValues
|
|
* Iterable of values or promises that may be pending, resolved, or
|
|
* rejected. When any is resolved or rejected, the returned promise will
|
|
* be resolved or rejected as to the given value or reason.
|
|
*
|
|
* @return A new promise that is fulfilled when any values are resolved or
|
|
* rejected. Its resolution value will be forwarded from the resolution
|
|
* value or rejection reason.
|
|
*/
|
|
Promise.race = function (aValues)
|
|
{
|
|
if (aValues == null || typeof(aValues[Symbol.iterator]) != "function") {
|
|
throw new Error("Promise.race() expects an iterable.");
|
|
}
|
|
|
|
return new Promise((resolve, reject) => {
|
|
for (let value of aValues) {
|
|
Promise.resolve(value).then(resolve, reject);
|
|
}
|
|
});
|
|
};
|
|
|
|
Promise.Debugging = {
|
|
/**
|
|
* Add an observer notified when an error is reported as uncaught.
|
|
*
|
|
* @param {function} observer A function notified when an error is
|
|
* reported as uncaught. Its arguments are
|
|
* {message, date, fileName, stack, lineNumber}
|
|
* All arguments are optional.
|
|
*/
|
|
addUncaughtErrorObserver: function(observer) {
|
|
PendingErrors.addObserver(observer);
|
|
},
|
|
|
|
/**
|
|
* Remove an observer added with addUncaughtErrorObserver
|
|
*
|
|
* @param {function} An observer registered with
|
|
* addUncaughtErrorObserver.
|
|
*/
|
|
removeUncaughtErrorObserver: function(observer) {
|
|
PendingErrors.removeObserver(observer);
|
|
},
|
|
|
|
/**
|
|
* Remove all the observers added with addUncaughtErrorObserver
|
|
*/
|
|
clearUncaughtErrorObservers: function() {
|
|
PendingErrors.removeAllObservers();
|
|
},
|
|
|
|
/**
|
|
* Force all pending errors to be reported immediately as uncaught.
|
|
* Note that this may cause some false positives.
|
|
*/
|
|
flushUncaughtErrors: function() {
|
|
PendingErrors.flush();
|
|
},
|
|
};
|
|
Object.freeze(Promise.Debugging);
|
|
|
|
Object.freeze(Promise);
|
|
|
|
// If module is defined, this file is loaded as a CommonJS module. Make sure
|
|
// Promise is exported in that case.
|
|
if (this.module) {
|
|
module.exports = Promise;
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//// PromiseWalker
|
|
|
|
/**
|
|
* This singleton object invokes the handlers registered on resolved and
|
|
* rejected promises, ensuring that processing is not recursive and is done in
|
|
* the same order as registration occurred on each promise.
|
|
*
|
|
* There is no guarantee on the order of execution of handlers registered on
|
|
* different promises.
|
|
*/
|
|
this.PromiseWalker = {
|
|
/**
|
|
* Singleton array of all the unprocessed handlers currently registered on
|
|
* resolved or rejected promises. Handlers are removed from the array as soon
|
|
* as they are processed.
|
|
*/
|
|
handlers: [],
|
|
|
|
/**
|
|
* Called when a promise needs to change state to be resolved or rejected.
|
|
*
|
|
* @param aPromise
|
|
* Promise that needs to change state. If this is already resolved or
|
|
* rejected, this method has no effect.
|
|
* @param aStatus
|
|
* New desired status, either STATUS_RESOLVED or STATUS_REJECTED.
|
|
* @param aValue
|
|
* Associated resolution value or rejection reason.
|
|
*/
|
|
completePromise: function (aPromise, aStatus, aValue)
|
|
{
|
|
// Do nothing if the promise is already resolved or rejected.
|
|
if (aPromise[N_INTERNALS].status != STATUS_PENDING) {
|
|
return;
|
|
}
|
|
|
|
// Resolving with another promise will cause this promise to eventually
|
|
// assume the state of the provided promise.
|
|
if (aStatus == STATUS_RESOLVED && aValue &&
|
|
typeof(aValue.then) == "function") {
|
|
aValue.then(this.completePromise.bind(this, aPromise, STATUS_RESOLVED),
|
|
this.completePromise.bind(this, aPromise, STATUS_REJECTED));
|
|
return;
|
|
}
|
|
|
|
// Change the promise status and schedule our handlers for processing.
|
|
aPromise[N_INTERNALS].status = aStatus;
|
|
aPromise[N_INTERNALS].value = aValue;
|
|
if (aPromise[N_INTERNALS].handlers.length > 0) {
|
|
this.schedulePromise(aPromise);
|
|
} else if (Cu && aStatus == STATUS_REJECTED) {
|
|
// This is a rejection and the promise is the last in the chain.
|
|
// For the time being we therefore have an uncaught error.
|
|
let id = PendingErrors.register(aValue);
|
|
let witness =
|
|
FinalizationWitnessService.make("promise-finalization-witness", id);
|
|
aPromise[N_INTERNALS].witness = [id, witness];
|
|
}
|
|
},
|
|
|
|
/**
|
|
* Sets up the PromiseWalker loop to start on the next tick of the event loop
|
|
*/
|
|
scheduleWalkerLoop: function()
|
|
{
|
|
this.walkerLoopScheduled = true;
|
|
|
|
// If this file is loaded on a worker thread, DOMPromise will not behave as
|
|
// expected: because native promises are not aware of nested event loops
|
|
// created by the debugger, their respective handlers will not be called
|
|
// until after leaving the nested event loop. The debugger server relies
|
|
// heavily on the use promises, so this could cause the debugger to hang.
|
|
//
|
|
// To work around this problem, any use of native promises in the debugger
|
|
// server should be avoided when it is running on a worker thread. Because
|
|
// it is still necessary to be able to schedule runnables on the event
|
|
// queue, the worker loader defines the function setImmediate as a
|
|
// per-module global for this purpose.
|
|
//
|
|
// If Cu is defined, this file is loaded on the main thread. Otherwise, it
|
|
// is loaded on the worker thread.
|
|
if (Cu) {
|
|
let stack = Components_ ? Components_.stack : null;
|
|
if (stack) {
|
|
DOMPromise.resolve().then(() => {
|
|
Cu.callFunctionWithAsyncStack(this.walkerLoop.bind(this), stack,
|
|
"Promise")
|
|
});
|
|
} else {
|
|
DOMPromise.resolve().then(() => this.walkerLoop());
|
|
}
|
|
} else {
|
|
setImmediate(this.walkerLoop);
|
|
}
|
|
},
|
|
|
|
/**
|
|
* Schedules the resolution or rejection handlers registered on the provided
|
|
* promise for processing.
|
|
*
|
|
* @param aPromise
|
|
* Resolved or rejected promise whose handlers should be processed. It
|
|
* is expected that this promise has at least one handler to process.
|
|
*/
|
|
schedulePromise: function (aPromise)
|
|
{
|
|
// Migrate the handlers from the provided promise to the global list.
|
|
for (let handler of aPromise[N_INTERNALS].handlers) {
|
|
this.handlers.push(handler);
|
|
}
|
|
aPromise[N_INTERNALS].handlers.length = 0;
|
|
|
|
// Schedule the walker loop on the next tick of the event loop.
|
|
if (!this.walkerLoopScheduled) {
|
|
this.scheduleWalkerLoop();
|
|
}
|
|
},
|
|
|
|
/**
|
|
* Indicates whether the walker loop is currently scheduled for execution on
|
|
* the next tick of the event loop.
|
|
*/
|
|
walkerLoopScheduled: false,
|
|
|
|
/**
|
|
* Processes all the known handlers during this tick of the event loop. This
|
|
* eager processing is done to avoid unnecessarily exiting and re-entering the
|
|
* JavaScript context for each handler on a resolved or rejected promise.
|
|
*
|
|
* This function is called with "this" bound to the PromiseWalker object.
|
|
*/
|
|
walkerLoop: function ()
|
|
{
|
|
// If there is more than one handler waiting, reschedule the walker loop
|
|
// immediately. Otherwise, use walkerLoopScheduled to tell schedulePromise()
|
|
// to reschedule the loop if it adds more handlers to the queue. This makes
|
|
// this walker resilient to the case where one handler does not return, but
|
|
// starts a nested event loop. In that case, the newly scheduled walker will
|
|
// take over. In the common case, the newly scheduled walker will be invoked
|
|
// after this one has returned, with no actual handler to process. This
|
|
// small overhead is required to make nested event loops work correctly, but
|
|
// occurs at most once per resolution chain, thus having only a minor
|
|
// impact on overall performance.
|
|
if (this.handlers.length > 1) {
|
|
this.scheduleWalkerLoop();
|
|
} else {
|
|
this.walkerLoopScheduled = false;
|
|
}
|
|
|
|
// Process all the known handlers eagerly.
|
|
while (this.handlers.length > 0) {
|
|
this.handlers.shift().process();
|
|
}
|
|
},
|
|
};
|
|
|
|
// Bind the function to the singleton once.
|
|
PromiseWalker.walkerLoop = PromiseWalker.walkerLoop.bind(PromiseWalker);
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//// Deferred
|
|
|
|
/**
|
|
* Returned by "Promise.defer" to provide a new promise along with methods to
|
|
* change its state.
|
|
*/
|
|
function Deferred()
|
|
{
|
|
this.promise = new Promise((aResolve, aReject) => {
|
|
this.resolve = aResolve;
|
|
this.reject = aReject;
|
|
});
|
|
Object.freeze(this);
|
|
}
|
|
|
|
Deferred.prototype = {
|
|
/**
|
|
* A newly created promise, initially in the pending state.
|
|
*/
|
|
promise: null,
|
|
|
|
/**
|
|
* Resolves the associated promise with the specified value, or propagates the
|
|
* state of an existing promise. If the associated promise has already been
|
|
* resolved or rejected, this method does nothing.
|
|
*
|
|
* This function is bound to its associated promise when "Promise.defer" is
|
|
* called, and can be called with any value of "this".
|
|
*
|
|
* @param aValue
|
|
* If this value is not a promise, including "undefined", it becomes
|
|
* the resolution value of the associated promise. If this value is a
|
|
* promise, then the associated promise will eventually assume the same
|
|
* state as the provided promise.
|
|
*
|
|
* @note Calling this method with a pending promise as the aValue argument,
|
|
* and then calling it again with another value before the promise is
|
|
* resolved or rejected, has unspecified behavior and should be avoided.
|
|
*/
|
|
resolve: null,
|
|
|
|
/**
|
|
* Rejects the associated promise with the specified reason. If the promise
|
|
* has already been resolved or rejected, this method does nothing.
|
|
*
|
|
* This function is bound to its associated promise when "Promise.defer" is
|
|
* called, and can be called with any value of "this".
|
|
*
|
|
* @param aReason
|
|
* The rejection reason for the associated promise. Although the
|
|
* reason can be "undefined", it is generally an Error object, like in
|
|
* exception handling.
|
|
*
|
|
* @note The aReason argument should not generally be a promise. In fact,
|
|
* using a rejected promise for the value of aReason would make the
|
|
* rejection reason equal to the rejected promise itself, not to the
|
|
* rejection reason of the rejected promise.
|
|
*/
|
|
reject: null,
|
|
};
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//// Handler
|
|
|
|
/**
|
|
* Handler registered on a promise by the "then" function.
|
|
*/
|
|
function Handler(aThisPromise, aOnResolve, aOnReject)
|
|
{
|
|
this.thisPromise = aThisPromise;
|
|
this.onResolve = aOnResolve;
|
|
this.onReject = aOnReject;
|
|
this.nextPromise = new Promise(() => {});
|
|
}
|
|
|
|
Handler.prototype = {
|
|
/**
|
|
* Promise on which the "then" method was called.
|
|
*/
|
|
thisPromise: null,
|
|
|
|
/**
|
|
* Unmodified resolution handler provided to the "then" method.
|
|
*/
|
|
onResolve: null,
|
|
|
|
/**
|
|
* Unmodified rejection handler provided to the "then" method.
|
|
*/
|
|
onReject: null,
|
|
|
|
/**
|
|
* New promise that will be returned by the "then" method.
|
|
*/
|
|
nextPromise: null,
|
|
|
|
/**
|
|
* Called after thisPromise is resolved or rejected, invokes the appropriate
|
|
* callback and propagates the result to nextPromise.
|
|
*/
|
|
process: function()
|
|
{
|
|
// The state of this promise is propagated unless a handler is defined.
|
|
let nextStatus = this.thisPromise[N_INTERNALS].status;
|
|
let nextValue = this.thisPromise[N_INTERNALS].value;
|
|
|
|
try {
|
|
// If a handler is defined for either resolution or rejection, invoke it
|
|
// to determine the state of the next promise, that will be resolved with
|
|
// the returned value, that can also be another promise.
|
|
if (nextStatus == STATUS_RESOLVED) {
|
|
if (typeof(this.onResolve) == "function") {
|
|
nextValue = this.onResolve.call(undefined, nextValue);
|
|
}
|
|
} else if (typeof(this.onReject) == "function") {
|
|
nextValue = this.onReject.call(undefined, nextValue);
|
|
nextStatus = STATUS_RESOLVED;
|
|
}
|
|
} catch (ex) {
|
|
|
|
// An exception has occurred in the handler.
|
|
|
|
if (ex && typeof ex == "object" && "name" in ex &&
|
|
ERRORS_TO_REPORT.indexOf(ex.name) != -1) {
|
|
|
|
// We suspect that the exception is a programmer error, so we now
|
|
// display it using dump(). Note that we do not use Cu.reportError as
|
|
// we assume that this is a programming error, so we do not want end
|
|
// users to see it. Also, if the programmer handles errors correctly,
|
|
// they will either treat the error or log them somewhere.
|
|
|
|
dump("*************************\n");
|
|
dump("A coding exception was thrown in a Promise " +
|
|
((nextStatus == STATUS_RESOLVED) ? "resolution":"rejection") +
|
|
" callback.\n");
|
|
dump("See https://developer.mozilla.org/Mozilla/JavaScript_code_modules/Promise.jsm/Promise\n\n");
|
|
dump("Full message: " + ex + "\n");
|
|
dump("Full stack: " + (("stack" in ex)?ex.stack:"not available") + "\n");
|
|
dump("*************************\n");
|
|
|
|
}
|
|
|
|
// Additionally, reject the next promise.
|
|
nextStatus = STATUS_REJECTED;
|
|
nextValue = ex;
|
|
}
|
|
|
|
// Propagate the newly determined state to the next promise.
|
|
PromiseWalker.completePromise(this.nextPromise, nextStatus, nextValue);
|
|
},
|
|
};
|