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-rw-r--r--toolkit/modules/PromiseMessage.jsm33
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diff --git a/toolkit/modules/PromiseMessage.jsm b/toolkit/modules/PromiseMessage.jsm
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+/* 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";
+
+this.EXPORTED_SYMBOLS = ["PromiseMessage"];
+
+var msgId = 0;
+
+var PromiseMessage = {
+ send(messageManager, name, data = {}) {
+ const id = `${name}_${msgId++}`;
+
+ // Make a copy of data so that the caller doesn't see us setting 'id':
+ // To a new object, assign data's props, and then override the id.
+ const dataCopy = Object.assign({}, data, {id});
+
+ // Send the message.
+ messageManager.sendAsyncMessage(name, dataCopy);
+
+ // Return a promise that resolves when we get a reply (a message of the same name).
+ return new Promise(resolve => {
+ messageManager.addMessageListener(name, function listener(reply) {
+ if (reply.data.id !== id) {
+ return;
+ }
+ messageManager.removeMessageListener(name, listener);
+ resolve(reply);
+ });
+ });
+ }
+};