Bug 1944147 - Option to turn off newtab for automated tests and other automation. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D269682

Author: ScottDowne

browser/modules/AboutNewTab.sys.mjs

@@ -21,6 +21,7 @@ const PREF_ACTIVITY_STREAM_DEBUG = "browser.newtabpage.activity-stream.debug";
 // AboutHomeStartupCache needs us in "quit-application", so stay alive longer.
 // TODO: We could better have a shared async shutdown blocker?
 const TOPIC_APP_QUIT = "profile-before-change";
+const PREF_SHOULD_INITIALIZE = "browser.newtabpage.shouldInitialize";
 
 export const AboutNewTab = {
   QueryInterface: ChromeUtils.generateQI([
@@ -50,6 +51,16 @@ export const AboutNewTab = {
       return;
     }
 
+    // For tests/automation: when false, newtab won't initialize in this session.
+    // Flipping after initialization has no effect on the current session.
+    const shouldInitialize = Services.prefs.getBoolPref(
+      PREF_SHOULD_INITIALIZE,
+      true
+    );
+    if (!shouldInitialize) {
+      return;
+    }
+
     Services.obs.addObserver(this, TOPIC_APP_QUIT);
     if (!AppConstants.RELEASE_OR_BETA) {
       XPCOMUtils.defineLazyPreferenceGetter(
@@ -238,11 +249,16 @@ export const AboutNewTab = {
       this.activityStream.uninit();
       this.activityStream = null;
     }
-    Services.obs.removeObserver(this, TOPIC_APP_QUIT);
-    Services.obs.removeObserver(
-      this,
-      lazy.TelemetryReportingPolicy.TELEMETRY_TOU_ACCEPTED_OR_INELIGIBLE
-    );
+    try {
+      Services.obs.removeObserver(this, TOPIC_APP_QUIT);
+      Services.obs.removeObserver(
+        this,
+        lazy.TelemetryReportingPolicy.TELEMETRY_TOU_ACCEPTED_OR_INELIGIBLE
+      );
+    } catch (e) {
+      // If init failed before registering these observers, removeObserver may throw.
+      // Safe to ignore during shutdown.
+    }
 
     this.initialized = false;
   },

browser/modules/test/browser/browser.toml

@@ -77,6 +77,8 @@ https_first_disabled = true
 ["browser_UsageTelemetry_uniqueOriginsVisitedInPast24Hours.js"]
 https_first_disabled = true
 
+["browser_aboutnewtab_init_gate.js"]
+
 ["browser_preloading_tab_moving.js"]
 
 ["browser_taskbar_preview.js"]

browser/modules/test/browser/browser_aboutnewtab_init_gate.js

@@ -0,0 +1,28 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const PREF = "browser.newtabpage.shouldInitialize";
+
+add_task(async function test_aboutnewtab_init_gate() {
+  ok(AboutNewTab.initialized, "AboutNewTab should initialize by default");
+
+  await SpecialPowers.pushPrefEnv({ set: [[PREF, false]] });
+
+  // Reset for a clean start.
+  AboutNewTab.uninit();
+
+  // Call init(); with pref=false, we should bail out early.
+  AboutNewTab.init();
+
+  ok(
+    !AboutNewTab.initialized,
+    "AboutNewTab should not be initialized when pref is false"
+  );
+
+  // Cleanup and reset.
+  await SpecialPowers.popPrefEnv();
+  AboutNewTab.init();
+  await AboutNewTab.onBrowserReady();
+});