1 files changed, 251 insertions, 0 deletions
diff --git a/toolkit/components/asyncshutdown/nsAsyncShutdown.sys.mjs b/toolkit/components/asyncshutdown/nsAsyncShutdown.sys.mjs
new file mode 100644
index 0000000000..23336a40bf
--- /dev/null
+++ b/toolkit/components/asyncshutdown/nsAsyncShutdown.sys.mjs
@@ -0,0 +1,251 @@
+/* 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/. */
+
+/**
+ * An implementation of nsIAsyncShutdown* based on AsyncShutdown.sys.mjs
+ */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+});
+
+/**
+ * Conversion between nsIPropertyBags and JS values.
+ * This uses a conservative approach to avoid losing data and doesn't throw.
+ * Don't use this if you need perfect serialization and deserialization.
+ */
+class PropertyBagConverter {
+  /**
+   * When the js value to convert is a primitive, it is stored in the property
+   * bag under a key with this name.
+   */
+  get primitiveProperty() {
+    return "PropertyBagConverter_primitive";
+  }
+
+  /**
+   * Converts from a PropertyBag to a JS value.
+   * @param {nsIPropertyBag} bag The PropertyBag to convert.
+   * @returns {jsval} A JS value.
+   */
+  propertyBagToJsValue(bag) {
+    if (!(bag instanceof Ci.nsIPropertyBag)) {
+      return null;
+    }
+    let result = {};
+    for (let { name, value: property } of bag.enumerator) {
+      let value = this.#toValue(property);
+      if (name == this.primitiveProperty) {
+        return value;
+      }
+      result[name] = value;
+    }
+    return result;
+  }
+
+  #toValue(property) {
+    if (property instanceof Ci.nsIPropertyBag) {
+      return this.propertyBagToJsValue(property);
+    }
+    if (["number", "boolean"].includes(typeof property)) {
+      return property;
+    }
+    try {
+      return JSON.parse(property);
+    } catch (ex) {
+      // Not JSON.
+    }
+    return property;
+  }
+
+  /**
+   * Converts from a JS value to a PropertyBag.
+   * @param {jsval} val JS value to convert.
+   * @returns {nsIPropertyBag} A PropertyBag.
+   * @note function is converted to "(function)" and undefined to null.
+   */
+  jsValueToPropertyBag(val) {
+    let bag = Cc["@mozilla.org/hash-property-bag;1"].createInstance(
+      Ci.nsIWritablePropertyBag
+    );
+    if (val && typeof val == "object") {
+      for (let k of Object.keys(val)) {
+        bag.setProperty(k, this.#fromValue(val[k]));
+      }
+    } else {
+      bag.setProperty(this.primitiveProperty, this.#fromValue(val));
+    }
+    return bag;
+  }
+
+  #fromValue(value) {
+    if (typeof value == "function") {
+      return "(function)";
+    }
+    if (value === undefined) {
+      value = null;
+    }
+    if (["number", "boolean", "string"].includes(typeof value)) {
+      return value;
+    }
+    return JSON.stringify(value);
+  }
+}
+
+/**
+ * Construct an instance of nsIAsyncShutdownClient from a
+ * AsyncShutdown.Barrier client.
+ *
+ * @param {object} moduleClient A client, as returned from the `client`
+ * property of an instance of `AsyncShutdown.Barrier`. This client will
+ * serve as back-end for methods `addBlocker` and `removeBlocker`.
+ * @constructor
+ */
+function nsAsyncShutdownClient(moduleClient) {
+  if (!moduleClient) {
+    throw new TypeError("nsAsyncShutdownClient expects one argument");
+  }
+  this._moduleClient = moduleClient;
+  this._byXpcomBlocker = new Map();
+}
+nsAsyncShutdownClient.prototype = {
+  get jsclient() {
+    return this._moduleClient;
+  },
+  get name() {
+    return this._moduleClient.name;
+  },
+  get isClosed() {
+    return this._moduleClient.isClosed;
+  },
+  addBlocker(
+    /* nsIAsyncShutdownBlocker*/ xpcomBlocker,
+    fileName,
+    lineNumber,
+    stack
+  ) {
+    // We need a Promise-based function with the same behavior as
+    // `xpcomBlocker`. Furthermore, to support `removeBlocker`, we
+    // need to ensure that we always get the same Promise-based
+    // function if we call several `addBlocker`/`removeBlocker` several
+    // times with the same `xpcomBlocker`.
+
+    if (this._byXpcomBlocker.has(xpcomBlocker)) {
+      throw new Error(
+        `We have already registered the blocker (${xpcomBlocker.name})`
+      );
+    }
+
+    // Ideally, this should be done with a WeakMap() with xpcomBlocker
+    // as a key, but XPCWrappedNative objects cannot serve as WeakMap keys, see
+    // bug 1834365.
+    const moduleBlocker = () =>
+      new Promise(
+        // This promise is never resolved. By opposition to AsyncShutdown
+        // blockers, `nsIAsyncShutdownBlocker`s are always lifted by calling
+        // `removeBlocker`.
+        () => xpcomBlocker.blockShutdown(this)
+      );
+
+    this._byXpcomBlocker.set(xpcomBlocker, moduleBlocker);
+    this._moduleClient.addBlocker(xpcomBlocker.name, moduleBlocker, {
+      fetchState: () =>
+        new PropertyBagConverter().propertyBagToJsValue(xpcomBlocker.state),
+      filename: fileName,
+      lineNumber,
+      stack,
+    });
+  },
+
+  removeBlocker(xpcomBlocker) {
+    let moduleBlocker = this._byXpcomBlocker.get(xpcomBlocker);
+    if (!moduleBlocker) {
+      return false;
+    }
+    this._byXpcomBlocker.delete(xpcomBlocker);
+    return this._moduleClient.removeBlocker(moduleBlocker);
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIAsyncShutdownClient"]),
+};
+
+/**
+ * Construct an instance of nsIAsyncShutdownBarrier from an instance
+ * of AsyncShutdown.Barrier.
+ *
+ * @param {object} moduleBarrier an instance if
+ * `AsyncShutdown.Barrier`. This instance will serve as back-end for
+ * all methods.
+ * @constructor
+ */
+function nsAsyncShutdownBarrier(moduleBarrier) {
+  this._client = new nsAsyncShutdownClient(moduleBarrier.client);
+  this._moduleBarrier = moduleBarrier;
+}
+nsAsyncShutdownBarrier.prototype = {
+  get state() {
+    return new PropertyBagConverter().jsValueToPropertyBag(
+      this._moduleBarrier.state
+    );
+  },
+  get client() {
+    return this._client;
+  },
+  wait(onReady) {
+    this._moduleBarrier.wait().then(() => {
+      onReady.done();
+    });
+    // By specification, _moduleBarrier.wait() cannot reject.
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIAsyncShutdownBarrier"]),
+};
+
+export function nsAsyncShutdownService() {
+  // Cache for the getters
+
+  for (let _k of [
+    // Parent process
+    "profileBeforeChange",
+    "profileChangeTeardown",
+    "quitApplicationGranted",
+    "sendTelemetry",
+
+    // Child processes
+    "contentChildShutdown",
+
+    // All processes
+    "webWorkersShutdown",
+    "xpcomWillShutdown",
+  ]) {
+    let k = _k;
+    Object.defineProperty(this, k, {
+      configurable: true,
+      get() {
+        delete this[k];
+        let wrapped = lazy.AsyncShutdown[k]; // May be undefined, if we're on the wrong process.
+        let result = wrapped ? new nsAsyncShutdownClient(wrapped) : undefined;
+        Object.defineProperty(this, k, {
+          value: result,
+        });
+        return result;
+      },
+    });
+  }
+
+  // Hooks for testing purpose
+  this.wrappedJSObject = {
+    _propertyBagConverter: PropertyBagConverter,
+  };
+}
+
+nsAsyncShutdownService.prototype = {
+  makeBarrier(name) {
+    return new nsAsyncShutdownBarrier(new lazy.AsyncShutdown.Barrier(name));
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIAsyncShutdownService"]),
+};