1 files changed, 186 insertions, 0 deletions
diff --git a/toolkit/jetpack/sdk/core/disposable.js b/toolkit/jetpack/sdk/core/disposable.js
new file mode 100644
index 000000000..19f7eaa9f
--- /dev/null
+++ b/toolkit/jetpack/sdk/core/disposable.js
@@ -0,0 +1,186 @@
+/* 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";
+
+module.metadata = {
+  "stability": "experimental"
+};
+
+const { Class } = require("./heritage");
+const { Observer, subscribe, unsubscribe, observe } = require("./observer");
+const { isWeak } = require("./reference");
+const SDKWeakSet = require("../lang/weak-set");
+
+const method = require("../../method/core");
+
+const unloadSubject = require('@loader/unload');
+const addonUnloadTopic = "sdk:loader:destroy";
+
+const uninstall = method("disposable/uninstall");
+exports.uninstall = uninstall;
+
+const shutdown = method("disposable/shutdown");
+exports.shutdown = shutdown;
+
+const disable = method("disposable/disable");
+exports.disable = disable;
+
+const upgrade = method("disposable/upgrade");
+exports.upgrade = upgrade;
+
+const downgrade = method("disposable/downgrade");
+exports.downgrade = downgrade;
+
+const unload = method("disposable/unload");
+exports.unload = unload;
+
+const dispose = method("disposable/dispose");
+exports.dispose = dispose;
+dispose.define(Object, object => object.dispose());
+
+const setup = method("disposable/setup");
+exports.setup = setup;
+setup.define(Object, (object, ...args) => object.setup(...args));
+
+// DisposablesUnloadObserver is the class which subscribe the
+// Observer Service to be notified when the add-on loader is
+// unloading to be able to dispose all the existent disposables.
+const DisposablesUnloadObserver = Class({
+  implements: [Observer],
+  initialize: function(...args) {
+    // Set of the non-weak disposables registered to be disposed.
+    this.disposables = new Set();
+    // Target of the weak disposables registered to be disposed
+    // (and tracked on this target using the SDK weak-set module).
+    this.weakDisposables = {};
+  },
+  subscribe(disposable) {
+    if (isWeak(disposable)) {
+      SDKWeakSet.add(this.weakDisposables, disposable);
+    } else {
+      this.disposables.add(disposable);
+    }
+  },
+  unsubscribe(disposable) {
+    if (isWeak(disposable)) {
+      SDKWeakSet.remove(this.weakDisposables, disposable);
+    } else {
+      this.disposables.delete(disposable);
+    }
+  },
+  tryUnloadDisposable(disposable) {
+    try {
+      if (disposable) {
+        unload(disposable);
+      }
+    } catch(e) {
+      console.error("Error unloading a",
+                    isWeak(disposable) ? "weak disposable" : "disposable",
+                    disposable, e);
+    }
+  },
+  unloadAll() {
+    // Remove all the subscribed disposables.
+    for (let disposable of this.disposables) {
+      this.tryUnloadDisposable(disposable);
+    }
+
+    this.disposables.clear();
+
+    // Remove all the subscribed weak disposables.
+    for (let disposable of SDKWeakSet.iterator(this.weakDisposables)) {
+      this.tryUnloadDisposable(disposable);
+    }
+
+    SDKWeakSet.clear(this.weakDisposables);
+  }
+});
+const disposablesUnloadObserver = new DisposablesUnloadObserver();
+
+// The DisposablesUnloadObserver instance is the only object which subscribes
+// the Observer Service directly, it observes add-on unload notifications in
+// order to trigger `unload` on all its subscribed disposables.
+observe.define(DisposablesUnloadObserver, (obj, subject, topic, data) => {
+  const isUnloadTopic = topic === addonUnloadTopic;
+  const isUnloadSubject = subject.wrappedJSObject === unloadSubject;
+  if (isUnloadTopic && isUnloadSubject) {
+    unsubscribe(disposablesUnloadObserver, addonUnloadTopic);
+    disposablesUnloadObserver.unloadAll();
+  }
+});
+
+subscribe(disposablesUnloadObserver, addonUnloadTopic, false);
+
+// Set's up disposable instance.
+const setupDisposable = disposable => {
+  disposablesUnloadObserver.subscribe(disposable);
+};
+exports.setupDisposable = setupDisposable;
+
+// Tears down disposable instance.
+const disposeDisposable = disposable => {
+  disposablesUnloadObserver.unsubscribe(disposable);
+};
+exports.disposeDisposable = disposeDisposable;
+
+// Base type that takes care of disposing it's instances on add-on unload.
+// Also makes sure to remove unload listener if it's already being disposed.
+const Disposable = Class({
+  initialize: function(...args) {
+    // First setup instance before initializing it's disposal. If instance
+    // fails to initialize then there is no instance to be disposed at the
+    // unload.
+    setup(this, ...args);
+    setupDisposable(this);
+  },
+  destroy: function(reason) {
+    // Destroying disposable removes unload handler so that attempt to dispose
+    // won't be made at unload & delegates to dispose.
+    disposeDisposable(this);
+    unload(this, reason);
+  },
+  setup: function() {
+    // Implement your initialize logic here.
+  },
+  dispose: function() {
+    // Implement your cleanup logic here.
+  }
+});
+exports.Disposable = Disposable;
+
+const unloaders = {
+  destroy: dispose,
+  uninstall: uninstall,
+  shutdown: shutdown,
+  disable: disable,
+  upgrade: upgrade,
+  downgrade: downgrade
+};
+
+const unloaded = new WeakMap();
+unload.define(Disposable, (disposable, reason) => {
+  if (!unloaded.get(disposable)) {
+    unloaded.set(disposable, true);
+    // Pick an unload handler associated with an unload
+    // reason (falling back to destroy if not found) and
+    // delegate unloading to it.
+    const unload = unloaders[reason] || unloaders.destroy;
+    unload(disposable);
+  }
+});
+
+// If add-on is disabled manually, it's being upgraded, downgraded
+// or uninstalled `dispose` is invoked to undo any changes that
+// has being done by it in this session.
+disable.define(Disposable, dispose);
+downgrade.define(Disposable, dispose);
+upgrade.define(Disposable, dispose);
+uninstall.define(Disposable, dispose);
+
+// If application is shut down no dispose is invoked as undo-ing
+// changes made by instance is likely to just waste of resources &
+// increase shutdown time. Although specefic components may choose
+// to implement shutdown handler that does something better.
+shutdown.define(Disposable, disposable => {});