Issue 3515 - Replace Prefs.onLoaded event by Prefs.isLoaded promise

lib/prefs.js

Index: lib/prefs.js
===================================================================
--- a/lib/prefs.js
+++ b/lib/prefs.js
@@ -169,12 +169,13 @@
   onChanged: new ext._EventTarget(),
 
   /**
-   * Fired when all preferences have been loaded. You must wait for
-   * this event before using preferences during extension initialization.
+   * A promise that is fullfilled when all preferences have been loaded.
+   * Wait for this promise to be fulfilled before using preferences during
+   * extension initialization.
    *
-   * @event
+   * @type {Promise}
    */
-  onLoaded: new ext._EventTarget()
+  isLoaded: null
 };
 
 function keyToPref(key)
@@ -224,14 +225,41 @@
   let prefs = Object.keys(defaults);
   prefs.forEach(addPreference);
 
-  let localLoaded = false;
-  let managedLoaded = false;
+  let localLoaded = new Promise(resolve => {
+    ext.storage.get(prefs.map(prefToKey), function(items)
+    {
+      for (let key in items)
+        overrides[keyToPref(key)] = items[key];
 
-  let checkLoaded = function()
+      resolve();
+    });
+  });
+
+  let managedLoaded = new Promise(resolve => {
+    if (require("info").platform == "chromium" && "managed" in chrome.storage)
+    {
+      chrome.storage.managed.get(null, function(items)
+      {
+        // Opera doesn't support chrome.storage.managed, but instead simply
+        // removing the API, Opera sets chrome.runtime.lastError when using it.
+        // So we have to retrieve that error, to prevent it from showing up
+        // in the console.
+        chrome.runtime.lastError;
+
+        for (let key in items)
+          defaults[key] = items[key];
+
+        resolve();
+      });
+    }
+    else
+    {
+      resolve();
+    }
+  });
+
+  function onLoaded()
   {
-    if (!localLoaded || !managedLoaded)
-      return;
-
     ext.storage.onChanged.addListener(function(changes)
     {
       for (let key in changes)
@@ -249,41 +277,9 @@
         }
       }
     });
+  }
 
-    Prefs.onLoaded._dispatch();
-  };
-
-  ext.storage.get(prefs.map(prefToKey), function(items)
-  {
-    for (let key in items)
-      overrides[keyToPref(key)] = items[key];
-
-    localLoaded = true;
-    checkLoaded();
-  });
-
-  if (require("info").platform == "chromium" && "managed" in chrome.storage)
-  {
-    chrome.storage.managed.get(null, function(items)
-    {
-      // Opera doesn't support chrome.storage.managed, but instead simply
-      // removing the API, Opera sets chrome.runtime.lastError when using it.
-      // So we have to retrieve that error, to prevent it from showing up
-      // in the console.
-      chrome.runtime.lastError;
-
-      for (let key in items)
-        defaults[key] = items[key];
-
-      managedLoaded = true;
-      checkLoaded();
-    });
-  }
-  else
-  {
-    managedLoaded = true;
-    checkLoaded();
-  }
+  Prefs.isLoaded = Promise.all([localLoaded, managedLoaded]).then(onLoaded);
 }
 
 init();