Add m-esr52 at 52.6.0

1 files changed, 515 insertions, 0 deletions

diff --git a/devtools/shared/task.js b/devtools/shared/task.js
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+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* eslint-disable spaced-comment */
+/* globals StopIteration */
+
+/**
+ * This module implements a subset of "Task.js" <http://taskjs.org/>.
+ * It is a copy of toolkit/modules/Task.jsm.  Please try not to
+ * diverge the API here.
+ *
+ * Paraphrasing from the Task.js site, tasks make sequential, asynchronous
+ * operations simple, using the power of JavaScript's "yield" operator.
+ *
+ * Tasks are built upon generator functions and promises, documented here:
+ *
+ * <https://developer.mozilla.org/en/JavaScript/Guide/Iterators_and_Generators>
+ * <http://wiki.commonjs.org/wiki/Promises/A>
+ *
+ * The "Task.spawn" function takes a generator function and starts running it as
+ * a task.  Every time the task yields a promise, it waits until the promise is
+ * fulfilled.  "Task.spawn" returns a promise that is resolved when the task
+ * completes successfully, or is rejected if an exception occurs.
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * const {Task} = require("devtools/shared/task");
+ *
+ * Task.spawn(function* () {
+ *
+ *   // This is our task. Let's create a promise object, wait on it and capture
+ *   // its resolution value.
+ *   let myPromise = getPromiseResolvedOnTimeoutWithValue(1000, "Value");
+ *   let result = yield myPromise;
+ *
+ *   // This part is executed only after the promise above is fulfilled (after
+ *   // one second, in this imaginary example).  We can easily loop while
+ *   // calling asynchronous functions, and wait multiple times.
+ *   for (let i = 0; i < 3; i++) {
+ *     result += yield getPromiseResolvedOnTimeoutWithValue(50, "!");
+ *   }
+ *
+ *   return "Resolution result for the task: " + result;
+ * }).then(function (result) {
+ *
+ *   // result == "Resolution result for the task: Value!!!"
+ *
+ *   // The result is undefined if no value was returned.
+ *
+ * }, function (exception) {
+ *
+ *   // Failure!  We can inspect or report the exception.
+ *
+ * });
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * This module implements only the "Task.js" interfaces described above, with no
+ * additional features to control the task externally, or do custom scheduling.
+ * It also provides the following extensions that simplify task usage in the
+ * most common cases:
+ *
+ * - The "Task.spawn" function also accepts an iterator returned by a generator
+ *   function, in addition to a generator function.  This way, you can call into
+ *   the generator function with the parameters you want, and with "this" bound
+ *   to the correct value.  Also, "this" is never bound to the task object when
+ *   "Task.spawn" calls the generator function.
+ *
+ * - In addition to a promise object, a task can yield the iterator returned by
+ *   a generator function.  The iterator is turned into a task automatically.
+ *   This reduces the syntax overhead of calling "Task.spawn" explicitly when
+ *   you want to recurse into other task functions.
+ *
+ * - The "Task.spawn" function also accepts a primitive value, or a function
+ *   returning a primitive value, and treats the value as the result of the
+ *   task.  This makes it possible to call an externally provided function and
+ *   spawn a task from it, regardless of whether it is an asynchronous generator
+ *   or a synchronous function.  This comes in handy when iterating over
+ *   function lists where some items have been converted to tasks and some not.
+ */
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+const Promise = require("promise");
+const defer = require("devtools/shared/defer");
+
+// The following error types are considered programmer errors, which should be
+// reported (possibly redundantly) so as to let programmers fix their code.
+const ERRORS_TO_REPORT = ["EvalError", "RangeError", "ReferenceError",
+                          "TypeError"];
+
+/**
+ * The Task currently being executed
+ */
+var gCurrentTask = null;
+
+/**
+ * If `true`, capture stacks whenever entering a Task and rewrite the
+ * stack any exception thrown through a Task.
+ */
+var gMaintainStack = false;
+
+/**
+ * Iterate through the lines of a string.
+ *
+ * @return Iterator<string>
+ */
+function* linesOf(string) {
+  let reLine = /([^\r\n])+/g;
+  let match;
+  while ((match = reLine.exec(string))) {
+    yield [match[0], match.index];
+  }
+}
+
+/**
+ * Detect whether a value is a generator.
+ *
+ * @param aValue
+ *        The value to identify.
+ * @return A boolean indicating whether the value is a generator.
+ */
+function isGenerator(value) {
+  return Object.prototype.toString.call(value) == "[object Generator]";
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//// Task
+
+/**
+ * This object provides the public module functions.
+ */
+var Task = {
+  /**
+   * Creates and starts a new task.
+   *
+   * @param task
+   *        - If you specify a generator function, it is called with no
+   *          arguments to retrieve the associated iterator.  The generator
+   *          function is a task, that is can yield promise objects to wait
+   *          upon.
+   *        - If you specify the iterator returned by a generator function you
+   *          called, the generator function is also executed as a task.  This
+   *          allows you to call the function with arguments.
+   *        - If you specify a function that is not a generator, it is called
+   *          with no arguments, and its return value is used to resolve the
+   *          returned promise.
+   *        - If you specify anything else, you get a promise that is already
+   *          resolved with the specified value.
+   *
+   * @return A promise object where you can register completion callbacks to be
+   *         called when the task terminates.
+   */
+  spawn: function (task) {
+    return createAsyncFunction(task).call(undefined);
+  },
+
+  /**
+   * Create and return an 'async function' that starts a new task.
+   *
+   * This is similar to 'spawn' except that it doesn't immediately start
+   * the task, it binds the task to the async function's 'this' object and
+   * arguments, and it requires the task to be a function.
+   *
+   * It simplifies the common pattern of implementing a method via a task,
+   * like this simple object with a 'greet' method that has a 'name' parameter
+   * and spawns a task to send a greeting and return its reply:
+   *
+   * let greeter = {
+   *   message: "Hello, NAME!",
+   *   greet: function(name) {
+   *     return Task.spawn((function* () {
+   *       return yield sendGreeting(this.message.replace(/NAME/, name));
+   *     }).bind(this);
+   *   })
+   * };
+   *
+   * With Task.async, the method can be declared succinctly:
+   *
+   * let greeter = {
+   *   message: "Hello, NAME!",
+   *   greet: Task.async(function* (name) {
+   *     return yield sendGreeting(this.message.replace(/NAME/, name));
+   *   })
+   * };
+   *
+   * While maintaining identical semantics:
+   *
+   * greeter.greet("Mitchell").then((reply) => { ... }); // behaves the same
+   *
+   * @param task
+   *        The task function to start.
+   *
+   * @return A function that starts the task function and returns its promise.
+   */
+  async: function (task) {
+    if (typeof (task) != "function") {
+      throw new TypeError("task argument must be a function");
+    }
+
+    return createAsyncFunction(task);
+  },
+
+  /**
+   * Constructs a special exception that, when thrown inside a legacy generator
+   * function (non-star generator), allows the associated task to be resolved
+   * with a specific value.
+   *
+   * Example: throw new Task.Result("Value");
+   */
+  Result: function (value) {
+    this.value = value;
+  }
+};
+
+function createAsyncFunction(task) {
+  let asyncFunction = function () {
+    let result = task;
+    if (task && typeof (task) == "function") {
+      if (task.isAsyncFunction) {
+        throw new TypeError(
+          "Cannot use an async function in place of a promise. " +
+          "You should either invoke the async function first " +
+          "or use 'Task.spawn' instead of 'Task.async' to start " +
+          "the Task and return its promise.");
+      }
+
+      try {
+        // Let's call into the function ourselves.
+        result = task.apply(this, arguments);
+      } catch (ex) {
+        if (ex instanceof Task.Result) {
+          return Promise.resolve(ex.value);
+        }
+        return Promise.reject(ex);
+      }
+    }
+
+    if (isGenerator(result)) {
+      // This is an iterator resulting from calling a generator function.
+      return new TaskImpl(result).deferred.promise;
+    }
+
+    // Just propagate the given value to the caller as a resolved promise.
+    return Promise.resolve(result);
+  };
+
+  asyncFunction.isAsyncFunction = true;
+
+  return asyncFunction;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//// TaskImpl
+
+/**
+ * Executes the specified iterator as a task, and gives access to the promise
+ * that is fulfilled when the task terminates.
+ */
+function TaskImpl(iterator) {
+  if (gMaintainStack) {
+    this._stack = (new Error()).stack;
+  }
+  this.deferred = defer();
+  this._iterator = iterator;
+  this._isStarGenerator = !("send" in iterator);
+  this._run(true);
+}
+
+TaskImpl.prototype = {
+  /**
+   * Includes the promise object where task completion callbacks are registered,
+   * and methods to resolve or reject the promise at task completion.
+   */
+  deferred: null,
+
+  /**
+   * The iterator returned by the generator function associated with this task.
+   */
+  _iterator: null,
+
+  /**
+   * Whether this Task is using a star generator.
+   */
+  _isStarGenerator: false,
+
+  /**
+   * Main execution routine, that calls into the generator function.
+   *
+   * @param sendResolved
+   *        If true, indicates that we should continue into the generator
+   *        function regularly (if we were waiting on a promise, it was
+   *        resolved). If true, indicates that we should cause an exception to
+   *        be thrown into the generator function (if we were waiting on a
+   *        promise, it was rejected).
+   * @param sendValue
+   *        Resolution result or rejection exception, if any.
+   */
+  _run: function (sendResolved, sendValue) {
+    try {
+      gCurrentTask = this;
+
+      if (this._isStarGenerator) {
+        try {
+          let result = sendResolved ? this._iterator.next(sendValue)
+                                    : this._iterator.throw(sendValue);
+
+          if (result.done) {
+            // The generator function returned.
+            this.deferred.resolve(result.value);
+          } else {
+            // The generator function yielded.
+            this._handleResultValue(result.value);
+          }
+        } catch (ex) {
+          // The generator function failed with an uncaught exception.
+          this._handleException(ex);
+        }
+      } else {
+        try {
+          let yielded = sendResolved ? this._iterator.send(sendValue)
+                                     : this._iterator.throw(sendValue);
+          this._handleResultValue(yielded);
+        } catch (ex) {
+          if (ex instanceof Task.Result) {
+            // The generator function threw the special exception that
+            // allows it to return a specific value on resolution.
+            this.deferred.resolve(ex.value);
+          } else if (ex instanceof StopIteration) {
+            // The generator function terminated with no specific result.
+            this.deferred.resolve(undefined);
+          } else {
+            // The generator function failed with an uncaught exception.
+            this._handleException(ex);
+          }
+        }
+      }
+    } finally {
+      //
+      // At this stage, the Task may have finished executing, or have
+      // walked through a `yield` or passed control to a sub-Task.
+      // Regardless, if we still own `gCurrentTask`, reset it. If we
+      // have not finished execution of this Task, re-entering `_run`
+      // will set `gCurrentTask` to `this` as needed.
+      //
+      // We just need to be careful here in case we hit the following
+      // pattern:
+      //
+      //   Task.spawn(foo);
+      //   Task.spawn(bar);
+      //
+      // Here, `foo` and `bar` may be interleaved, so when we finish
+      // executing `foo`, `gCurrentTask` may actually either `foo` or
+      // `bar`. If `gCurrentTask` has already been set to `bar`, leave
+      // it be and it will be reset to `null` once `bar` is complete.
+      //
+      if (gCurrentTask == this) {
+        gCurrentTask = null;
+      }
+    }
+  },
+
+  /**
+   * Handle a value yielded by a generator.
+   *
+   * @param value
+   *        The yielded value to handle.
+   */
+  _handleResultValue: function (value) {
+    // If our task yielded an iterator resulting from calling another
+    // generator function, automatically spawn a task from it, effectively
+    // turning it into a promise that is fulfilled on task completion.
+    if (isGenerator(value)) {
+      value = Task.spawn(value);
+    }
+
+    if (value && typeof (value.then) == "function") {
+      // We have a promise object now. When fulfilled, call again into this
+      // function to continue the task, with either a resolution or rejection
+      // condition.
+      value.then(this._run.bind(this, true),
+                  this._run.bind(this, false));
+    } else {
+      // If our task yielded a value that is not a promise, just continue and
+      // pass it directly as the result of the yield statement.
+      this._run(true, value);
+    }
+  },
+
+  /**
+   * Handle an uncaught exception thrown from a generator.
+   *
+   * @param exception
+   *        The uncaught exception to handle.
+   */
+  _handleException: function (exception) {
+    gCurrentTask = this;
+
+    if (exception && typeof exception == "object" && "stack" in exception) {
+      let stack = exception.stack;
+
+      if (gMaintainStack &&
+          exception._capturedTaskStack != this._stack &&
+          typeof stack == "string") {
+        // Rewrite the stack for more readability.
+
+        let bottomStack = this._stack;
+
+        stack = Task.Debugging.generateReadableStack(stack);
+
+        exception.stack = stack;
+
+        // If exception is reinjected in the same task and rethrown,
+        // we don't want to perform the rewrite again.
+        exception._capturedTaskStack = bottomStack;
+      } else if (!stack) {
+        stack = "Not available";
+      }
+
+      if ("name" in exception &&
+          ERRORS_TO_REPORT.indexOf(exception.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 and uncaught in a Task.\n\n");
+        dump("Full message: " + exception + "\n");
+        dump("Full stack: " + exception.stack + "\n");
+        dump("*************************\n");
+      }
+    }
+
+    this.deferred.reject(exception);
+  },
+
+  get callerStack() {
+    // Cut `this._stack` at the last line of the first block that
+    // contains task.js, keep the tail.
+    for (let [line, index] of linesOf(this._stack || "")) {
+      if (line.indexOf("/task.js:") == -1) {
+        return this._stack.substring(index);
+      }
+    }
+    return "";
+  }
+};
+
+Task.Debugging = {
+
+  /**
+   * Control stack rewriting.
+   *
+   * If `true`, any exception thrown from a Task will be rewritten to
+   * provide a human-readable stack trace. Otherwise, stack traces will
+   * be left unchanged.
+   *
+   * There is a (small but existing) runtime cost associated to stack
+   * rewriting, so you should probably not activate this in production
+   * code.
+   *
+   * @type {bool}
+   */
+  get maintainStack() {
+    return gMaintainStack;
+  },
+  set maintainStack(x) {
+    if (!x) {
+      gCurrentTask = null;
+    }
+    gMaintainStack = x;
+    return x;
+  },
+
+  /**
+   * Generate a human-readable stack for an error raised in
+   * a Task.
+   *
+   * @param {string} topStack The stack provided by the error.
+   * @param {string=} prefix Optionally, a prefix for each line.
+   */
+  generateReadableStack: function (topStack, prefix = "") {
+    if (!gCurrentTask) {
+      return topStack;
+    }
+
+    // Cut `topStack` at the first line that contains task.js, keep the head.
+    let lines = [];
+    for (let [line] of linesOf(topStack)) {
+      if (line.indexOf("/task.js:") != -1) {
+        break;
+      }
+      lines.push(prefix + line);
+    }
+    if (!prefix) {
+      lines.push(gCurrentTask.callerStack);
+    } else {
+      for (let [line] of linesOf(gCurrentTask.callerStack)) {
+        lines.push(prefix + line);
+      }
+    }
+
+    return lines.join("\n");
+  }
+};
+
+exports.Task = Task;