1 files changed, 241 insertions, 0 deletions
diff --git a/toolkit/modules/tests/PromiseTestUtils.jsm b/toolkit/modules/tests/PromiseTestUtils.jsm
new file mode 100644
index 000000000..d60b785a5
--- /dev/null
+++ b/toolkit/modules/tests/PromiseTestUtils.jsm
@@ -0,0 +1,241 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Detects and reports unhandled rejections during test runs. Test harnesses
+ * will fail tests in this case, unless the test whitelists itself.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "PromiseTestUtils",
+];
+
+const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/Services.jsm", this);
+
+// Keep "JSMPromise" separate so "Promise" still refers to DOM Promises.
+let JSMPromise = Cu.import("resource://gre/modules/Promise.jsm", {}).Promise;
+
+// For now, we need test harnesses to provide a reference to Assert.jsm.
+let Assert = null;
+
+this.PromiseTestUtils = {
+  /**
+   * Array of objects containing the details of the Promise rejections that are
+   * currently left uncaught. This includes DOM Promise and Promise.jsm. When
+   * rejections in DOM Promises are consumed, they are removed from this list.
+   *
+   * The objects contain at least the following properties:
+   * {
+   *   message: The error message associated with the rejection, if any.
+   *   date: Date object indicating when the rejection was observed.
+   *   id: For DOM Promise only, the Promise ID from PromiseDebugging. This is
+   *       only used for tracking and should not be checked by the callers.
+   *   stack: nsIStackFrame, SavedFrame, or string indicating the stack at the
+   *          time the rejection was triggered. May also be null if the
+   *          rejection was triggered while a script was on the stack.
+   * }
+   */
+  _rejections: [],
+
+  /**
+   * When an uncaught rejection is detected, it is ignored if one of the
+   * functions in this array returns true when called with the rejection details
+   * as its only argument. When a function matches an expected rejection, it is
+   * then removed from the array.
+   */
+  _rejectionIgnoreFns: [],
+
+  /**
+   * Called only by the test infrastructure, registers the rejection observers.
+   *
+   * This should be called only once, and a matching "uninit" call must be made
+   * or the tests will crash on shutdown.
+   */
+  init() {
+    if (this._initialized) {
+      Cu.reportError("This object was already initialized.");
+      return;
+    }
+
+    PromiseDebugging.addUncaughtRejectionObserver(this);
+
+    // Promise.jsm rejections are only reported to this observer when requested,
+    // so we don't have to store a key to remove them when consumed.
+    JSMPromise.Debugging.addUncaughtErrorObserver(
+                            rejection => this._rejections.push(rejection));
+
+    this._initialized = true;
+  },
+  _initialized: false,
+
+  /**
+   * Called only by the test infrastructure, unregisters the observers.
+   */
+  uninit() {
+    if (!this._initialized) {
+      return;
+    }
+
+    PromiseDebugging.removeUncaughtRejectionObserver(this);
+    JSMPromise.Debugging.clearUncaughtErrorObservers();
+
+    this._initialized = false;
+  },
+
+  /**
+   * Called only by the test infrastructure, spins the event loop until the
+   * messages for pending DOM Promise rejections have been processed.
+   */
+  ensureDOMPromiseRejectionsProcessed() {
+    let observed = false;
+    let observer = {
+      onLeftUncaught: promise => {
+        if (PromiseDebugging.getState(promise).reason ===
+            this._ensureDOMPromiseRejectionsProcessedReason) {
+          observed = true;
+        }
+      },
+      onConsumed() {},
+    };
+
+    PromiseDebugging.addUncaughtRejectionObserver(observer);
+    Promise.reject(this._ensureDOMPromiseRejectionsProcessedReason);
+    while (!observed) {
+      Services.tm.mainThread.processNextEvent(true);
+    }
+    PromiseDebugging.removeUncaughtRejectionObserver(observer);
+  },
+  _ensureDOMPromiseRejectionsProcessedReason: {},
+
+  /**
+   * Called only by the tests for PromiseDebugging.addUncaughtRejectionObserver
+   * and for JSMPromise.Debugging, disables the observers in this module.
+   */
+  disableUncaughtRejectionObserverForSelfTest() {
+    this.uninit();
+  },
+
+  /**
+   * Called by tests that have been whitelisted, disables the observers in this
+   * module. For new tests where uncaught rejections are expected, you should
+   * use the more granular expectUncaughtRejection function instead.
+   */
+  thisTestLeaksUncaughtRejectionsAndShouldBeFixed() {
+    this.uninit();
+  },
+
+  /**
+   * Sets or updates the Assert object instance to be used for error reporting.
+   */
+  set Assert(assert) {
+    Assert = assert;
+  },
+
+  // UncaughtRejectionObserver
+  onLeftUncaught(promise) {
+    let message = "(Unable to convert rejection reason to string.)";
+    try {
+      let reason = PromiseDebugging.getState(promise).reason;
+      if (reason === this._ensureDOMPromiseRejectionsProcessedReason) {
+        // Ignore the special promise for ensureDOMPromiseRejectionsProcessed.
+        return;
+      }
+      message = reason.message || ("" + reason);
+    } catch (ex) {}
+
+    // It's important that we don't store any reference to the provided Promise
+    // object or its value after this function returns in order to avoid leaks.
+    this._rejections.push({
+      id: PromiseDebugging.getPromiseID(promise),
+      message,
+      date: new Date(),
+      stack: PromiseDebugging.getRejectionStack(promise),
+    });
+  },
+
+  // UncaughtRejectionObserver
+  onConsumed(promise) {
+    // We don't expect that many unhandled rejections will appear at the same
+    // time, so the algorithm doesn't need to be optimized for that case.
+    let id = PromiseDebugging.getPromiseID(promise);
+    let index = this._rejections.findIndex(rejection => rejection.id == id);
+    // If we get a consumption notification for a rejection that was left
+    // uncaught before this module was initialized, we can safely ignore it.
+    if (index != -1) {
+      this._rejections.splice(index, 1);
+    }
+  },
+
+  /**
+   * Informs the test suite that the test code will generate a Promise rejection
+   * that will still be unhandled when the test file terminates.
+   *
+   * This method must be called once for each instance of Promise that is
+   * expected to be uncaught, even if the rejection reason is the same for each
+   * instance.
+   *
+   * If the expected rejection does not occur, the test will fail.
+   *
+   * @param regExpOrCheckFn
+   *        This can either be a regular expression that should match the error
+   *        message of the rejection, or a check function that is invoked with
+   *        the rejection details object as its first argument.
+   */
+  expectUncaughtRejection(regExpOrCheckFn) {
+    let checkFn = !("test" in regExpOrCheckFn) ? regExpOrCheckFn :
+                  rejection => regExpOrCheckFn.test(rejection.message);
+    this._rejectionIgnoreFns.push(checkFn);
+  },
+
+  /**
+   * Fails the test if there are any uncaught rejections at this time that have
+   * not been whitelisted using expectUncaughtRejection.
+   *
+   * Depending on the configuration of the test suite, this function might only
+   * report the details of the first uncaught rejection that was generated.
+   *
+   * This is called by the test suite at the end of each test function.
+   */
+  assertNoUncaughtRejections() {
+    // Ask Promise.jsm to report all uncaught rejections to the observer now.
+    JSMPromise.Debugging.flushUncaughtErrors();
+
+    // If there is any uncaught rejection left at this point, the test fails.
+    while (this._rejections.length > 0) {
+      let rejection = this._rejections.shift();
+
+      // If one of the ignore functions matches, ignore the rejection, then
+      // remove the function so that each function only matches one rejection.
+      let index = this._rejectionIgnoreFns.findIndex(f => f(rejection));
+      if (index != -1) {
+        this._rejectionIgnoreFns.splice(index, 1);
+        continue;
+      }
+
+      // Report the error. This operation can throw an exception, depending on
+      // the configuration of the test suite that handles the assertion.
+      Assert.ok(false,
+                `A promise chain failed to handle a rejection:` +
+                ` ${rejection.message} - rejection date: ${rejection.date}`+
+                ` - stack: ${rejection.stack}`);
+    }
+  },
+
+  /**
+   * Fails the test if any rejection indicated by expectUncaughtRejection has
+   * not yet been reported at this time.
+   *
+   * This is called by the test suite at the end of each test file.
+   */
+  assertNoMoreExpectedRejections() {
+    // Only log this condition is there is a failure.
+    if (this._rejectionIgnoreFns.length > 0) {
+      Assert.equal(this._rejectionIgnoreFns.length, 0,
+             "Unable to find a rejection expected by expectUncaughtRejection.");
+    }
+  },
+};