Bug 1968779 - Wait for builtin-newtab.js to signal that it has finished onStartup before allowing ActivityStream to be instantiated. r=pdahiya

Differential Revision: https://phabricator.services.mozilla.com/D251397

browser/components/newtab/AboutNewTabRedirector.sys.mjs

@@ -464,10 +464,16 @@ class BaseAboutNewTabRedirector {
 export class AboutNewTabRedirectorParent extends BaseAboutNewTabRedirector {
   #addonInitialized = false;
   #suspendedChannels = [];
+  #addonInitializedPromise = null;
+  #addonInitializedResolver = null;
 
   constructor() {
     super();
 
+    let { promise, resolve } = Promise.withResolvers();
+    this.#addonInitializedPromise = promise;
+    this.#addonInitializedResolver = resolve;
+
     ChromeUtils.registerWindowActor("AboutNewTab", {
       parent: {
         esModuleURI: "resource:///actors/AboutNewTabParent.sys.mjs",
@@ -499,18 +505,30 @@ export class AboutNewTabRedirectorParent extends BaseAboutNewTabRedirector {
    * Waits for the AddonManager to be fully initialized, and for the built-in
    * addon to be ready. Once that's done, it tterates any suspended channels and
    * resumes them, now that the built-in addon has been set up.
-   *
-   * @returns {Promise<undefined>}
-   *   Resolves when the built-in addon has initialized and all suspended
-   *   channels are resumed.
    */
-  builtInAddonInitialized() {
+  notifyBuiltInAddonInitialized() {
     this.#addonInitialized = true;
 
     for (let suspendedChannel of this.#suspendedChannels) {
       suspendedChannel.resume();
     }
     this.#suspendedChannels = [];
+    this.#addonInitializedResolver();
+  }
+
+  /**
+   * Returns a Promise that reoslves when the newtab built-in addon has notified
+   * that it has finished initializing. If this is somehow checked when
+   * BROWSER_NEWTAB_AS_ADDON is not true, then this always resolves.
+   *
+   * @type {Promise<undefined>}
+   */
+  get promiseBuiltInAddonInitialized() {
+    if (!AppConstants.BROWSER_NEWTAB_AS_ADDON) {
+      return Promise.resolve();
+    }
+
+    return this.#addonInitializedPromise;
   }
 
   newChannel(uri, loadInfo) {

browser/extensions/newtab/webext-glue/builtin-newtab.js

@@ -48,45 +48,51 @@ this.builtin_newtab = class extends ExtensionAPI {
       return;
     }
 
-    const { rootURI } = this.extension;
+    try {
+      const { rootURI } = this.extension;
 
-    resProto.setSubstitutionWithFlags(
-      ResourceSubstitution,
-      rootURI,
-      Ci.nsISubstitutingProtocolHandler.ALLOW_CONTENT_ACCESS
-    );
-
-    let aomStartup = Cc[
-      "@mozilla.org/addons/addon-manager-startup;1"
-    ].getService(Ci.amIAddonManagerStartup);
-    const manifestURI = Services.io.newURI(
-      "manifest.json",
-      null,
-      this.extension.rootURI
-    );
-    this.#chromeHandle = aomStartup.registerChrome(manifestURI, [
-      ["content", "newtab", "data/content", "contentaccessible=yes"],
-    ]);
-
-    let redirector = Cc[
-      "@mozilla.org/network/protocol/about;1?what=newtab"
-    ].getService(Ci.nsIAboutModule).wrappedJSObject;
-
-    if (this.extension.rootURI.spec.endsWith("newtab@mozilla.org.xpi!/")) {
-      // We must be a train-hopped XPI running in this app. This means we
-      // may have Fluent files or Glean pings/metrics to register dynamically.
-      const newtabFileSource = new L10nFileSource(
-        "newtab",
-        "app",
-        SUPPORTED_LOCALES,
-        `resource://newtab/locales/{locale}/`
+      resProto.setSubstitutionWithFlags(
+        ResourceSubstitution,
+        rootURI,
+        Ci.nsISubstitutingProtocolHandler.ALLOW_CONTENT_ACCESS
       );
-      L10nRegistry.getInstance().registerSources([newtabFileSource]);
 
-      // Dynamically register any Glean pings/metrics here.
-      this.registerMetricsFromJson();
+      let aomStartup = Cc[
+        "@mozilla.org/addons/addon-manager-startup;1"
+      ].getService(Ci.amIAddonManagerStartup);
+      const manifestURI = Services.io.newURI(
+        "manifest.json",
+        null,
+        this.extension.rootURI
+      );
+      this.#chromeHandle = aomStartup.registerChrome(manifestURI, [
+        ["content", "newtab", "data/content", "contentaccessible=yes"],
+      ]);
+
+      let redirector = Cc[
+        "@mozilla.org/network/protocol/about;1?what=newtab"
+      ].getService(Ci.nsIAboutModule).wrappedJSObject;
+
+      if (this.extension.rootURI.spec.endsWith("newtab@mozilla.org.xpi!/")) {
+        // We must be a train-hopped XPI running in this app. This means we
+        // may have Fluent files or Glean pings/metrics to register dynamically.
+        const newtabFileSource = new L10nFileSource(
+          "newtab",
+          "app",
+          SUPPORTED_LOCALES,
+          `resource://newtab/locales/{locale}/`
+        );
+        L10nRegistry.getInstance().registerSources([newtabFileSource]);
+
+        // Dynamically register any Glean pings/metrics here.
+        this.registerMetricsFromJson();
+      }
+      redirector.notifyBuiltInAddonInitialized();
+      Glean.newtab.addonReadySuccess.set(true);
+    } catch(e) {
+      Glean.newtab.addonReadySuccess.set(false);
+      throw e;
     }
-    redirector.builtInAddonInitialized();
   }
 
   onShutdown() {

browser/modules/AboutNewTab.sys.mjs

@@ -10,7 +10,6 @@ const lazy = {};
 ChromeUtils.defineESModuleGetters(lazy, {
   ActivityStream: "resource://newtab/lib/ActivityStream.sys.mjs",
   AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
-  AddonManagerPrivate: "resource://gre/modules/AddonManager.sys.mjs",
   ObjectUtils: "resource://gre/modules/ObjectUtils.sys.mjs",
 });
 
@@ -160,28 +159,13 @@ export const AboutNewTab = {
     }
 
     if (AppConstants.BROWSER_NEWTAB_AS_ADDON) {
-      let addonPolicy = WebExtensionPolicy.getByID(BUILTIN_ADDON_ID);
-      if (!addonPolicy) {
-        // If this is the first time that the build flag was set to true, we
-        // might not yet have refreshed the addon database cache yet, in which
-        // case the addonPolicy will be null. In that case, we'll wait for the
-        // database to be ready before proceeding.
-        //
-        // We don't always just wait for the databaseReady Promise to resolve
-        // in order to avoid regressing newtab render times by needlessly
-        // going back to the event loop.
-        await lazy.AddonManagerPrivate.databaseReady;
-        addonPolicy = WebExtensionPolicy.getByID(BUILTIN_ADDON_ID);
-      }
+      // Wait until the built-in addon has reported that it has finished
+      // initializing.
+      let redirector = Cc[
+        "@mozilla.org/network/protocol/about;1?what=newtab"
+      ].getService(Ci.nsIAboutModule).wrappedJSObject;
 
-      if (!addonPolicy) {
-        // Something's gone very wrong here, and we should collect telemetry
-        // about it.
-        Glean.newtab.addonReadySuccess.set(false);
-      } else {
-        await addonPolicy.readyPromise;
-        Glean.newtab.addonReadySuccess.set(true);
-      }
+      await redirector.promiseBuiltInAddonInitialized;
     } else {
       // We may have had the built-in addon installed in the past. Since the
       // flag is false, let's go ahead and remove it. We don't need to await on