Issue 4579 - Promisify APIs

ext/common.js

Index: ext/common.js
===================================================================
--- a/ext/common.js
+++ b/ext/common.js
@@ -20,16 +20,85 @@
 (function()
 {
   // Both Edge and Mozilla Web Extensions use the namespace
   // 'browser' instead of 'chrome'. Edge has chrome namespace defined,
   // in some cases, but only with one property: 'app'.
   if (typeof chrome == "undefined" || typeof chrome.extension == "undefined")
     window.chrome = window.browser;
 
+  const asyncAPIs = [

[Manish Jethani, 2017/10/11 19:23:51]

This is the list of async APIs we actually use.

Ideally this would be a tree of objects rather than a list of strings, but there
are only so many of these, it's slightly inefficient but it doesn't matter. It's
definitely easier to maintain this way.

+    "contextMenus.removeAll",
+    "devtools.panels.create",
+    "notifications.clear",
+    "notifications.create",
+    "runtime.openOptionsPage",
+    "runtime.sendMessage",
+    "runtime.setUninstallURL",
+    "storage.local.get",
+    "storage.local.remove",
+    "storage.local.set",
+    "storage.managed.get",
+    "tabs.create",
+    "tabs.get",
+    "tabs.insertCSS",
+    "tabs.query",
+    "tabs.reload",
+    "tabs.sendMessage",
+    "tabs.update",
+    "webNavigation.getAllFrames",
+    "webRequest.handlerBehaviorChanged",
+    "windows.create",
+    "windows.update"
+  ];
+
+  function wrapAPI(api, object)
+  {
+    if (!object)
+      return;
+
+    let [root, ...subPath] = api.split(".");
+
+    if (subPath.length > 0)
+    {
+      wrapAPI(subPath.join("."), object[root]);
+      return;
+    }
+
+    let func = object[root];
+    object[root] = function(...args)
+    {
+      if (typeof args[args.length - 1] == "function")
+        return func.apply(object, args);
+
+      // If the last argument is undefined, we drop it from the list assuming
+      // it stands for the optional callback. We must do this, because we have
+      // to replace it with our own callback. If we simply append our own
+      // callback to the list, it won't match the signature of the function and
+      // will cause an exception.
+      if (typeof args[args.length - 1] == "undefined")

[Manish Jethani, 2017/10/11 19:23:51]

This should work, but if it doesn't we can always use the arity of the function.

+        args.pop();
+
+      return new Promise((resolve, reject) =>
+      {
+        func.call(object, ...args, result =>
+        {
+          let error = chrome.runtime.lastError;

[Manish Jethani, 2017/10/11 19:23:51]

It's OK to refer to chrome directly here. It will be replaced with browser.

+          if (error)
+            reject(error);
+          else
+            resolve(result);
+        });
+      });
+    };
+  }
+
+  for (let api of asyncAPIs)
+    wrapAPI(api, chrome);
+
   window.ext = {};
 
   let EventTarget = ext._EventTarget = function()
   {
     this._listeners = new Set();
   };
   EventTarget.prototype = {
     addListener(listener)