Issue 4580 - Stop using ext.onMessage in background page

lib/messaging.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /** @module messaging */
 
 "use strict";
 
 const {EventEmitter} = require("events");
 
 /**
- * Communication port wrapping ext.onMessage to receive messages.
+ * Communication port wrapping runtime.onMessage to receive messages.
  *
  * @constructor
  */
 function Port()
 {
   this._eventEmitter = new EventEmitter();
   this._onMessage = this._onMessage.bind(this);
-  ext.onMessage.addListener(this._onMessage);
+  browser.runtime.onMessage.addListener(this._onMessage);
 }
 
 Port.prototype = {
-  _onMessage(message, sender, sendResponse)
+  _onMessage(message, sender)
   {
-    let async = false;
-    let callbacks = this._eventEmitter.listeners(message.type);
-
-    for (let callback of callbacks)
+    // Add "page" and "frame" if the message was sent by a content script.

[Manish Jethani, 2018/03/22 19:56:55]

This used to be in ext/background.js

+    // If sent by popup or the background page itself, there is no "tab".
+    if ("tab" in sender)
     {
-      let response = callback(message, sender);
-
-      if (response && typeof response.then == "function")
-      {
-        response.then(
-          sendResponse,
-          reason =>
-          {
-            console.error(reason);
-            sendResponse(undefined);
-          }
-        );
-        async = true;
-      }
-      else if (typeof response != "undefined")
-      {
-        sendResponse(response);
-      }
+      sender = {
+        page: new ext.Page(sender.tab),
+        frame: new ext.Frame(sender.tab.id, sender.frameId, sender.url)
+      };
     }
 
-    return async;
+    // The message sender receives only the first response.

[Manish Jethani, 2018/03/22 19:56:55]

Note: using Promise.race here to resolve with first resolved value, which is
equivalent to what was happening earlier, but we could also just use Promise.all
and return all resolved values (but this will require more changes elsewhere and
also the response might take longer).

+    // https://developer.chrome.com/apps/messaging
+    // https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/runtime/onMessage
+    return Promise.race(
+      this._eventEmitter.listeners(message.type)
+      .map(callback => callback(message, sender))
+      .filter(response => typeof response != "undefined")
+    );
   },
 
   /**
    * Function to be called when a particular message is received.
    *
    * @callback Port~messageCallback
    * @param {object} message
    * @param {object} sender
    * @return The callback can return undefined (no response),
    *         a value (response to be sent to sender immediately)
@@ skipping 21 matching lines @@
   off(name, callback)
   {
     this._eventEmitter.off(name, callback);
   },
 
   /**
    * Disables the port and makes it stop listening to incoming messages.
    */
   disconnect()
   {
-    ext.onMessage.removeListener(this._onMessage);
+    brower.runtime.onMessage.removeListener(this._onMessage);
   }
 };
 
 /**
  * The default port to receive messages.
  *
  * @type {Port}
  */
 exports.port = new Port();
 
 /**
  * Creates a new port that is disconnected when the given window is unloaded.
  *
  * @param {Window} window
  * @return {Port}
  */
 exports.getPort = function(window)
 {
   let port = new Port();
   window.addEventListener("unload", () =>
   {
     port.disconnect();
   });
   return port;
 };