Bug 1792816 - Always update the search engine placeholder name. r=Standard8

Differential Revision: https://phabricator.services.mozilla.com/D165795

browser/base/content/browser.js

@@ -42,6 +42,7 @@ ChromeUtils.defineESModuleGetters(this, {
   PromptUtils: "resource://gre/modules/PromptUtils.sys.mjs",
   Sanitizer: "resource:///modules/Sanitizer.sys.mjs",
   ScreenshotsUtils: "resource:///modules/ScreenshotsUtils.sys.mjs",
+  SearchUIUtils: "resource:///modules/SearchUIUtils.sys.mjs",
   SessionStartup: "resource:///modules/sessionstore/SessionStartup.sys.mjs",
   SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
   ShortcutUtils: "resource://gre/modules/ShortcutUtils.sys.mjs",
@@ -1970,6 +1971,7 @@ var gBrowserInit = {
 
     BookmarkingUI.init();
     BrowserSearch.delayedStartupInit();
+    SearchUIUtils.init();
     gProtectionsHandler.init();
     HomePage.delayedStartup().catch(console.error);
 
@@ -3971,7 +3973,11 @@ const BrowserSearch = {
       ? Services.search.getDefaultPrivate
       : Services.search.getDefault;
     let defaultEngine = await getDefault();
-
+    if (!this._searchInitComplete) {
+      // If we haven't finished initialising, ensure the placeholder
+      // preference is set for the next startup.
+      SearchUIUtils.updatePlaceholderNamePreference(defaultEngine, isPrivate);
+    }
     this._updateURLBarPlaceholder(defaultEngine.name, isPrivate, delayUpdate);
   },
 
@@ -3994,12 +4000,7 @@ const BrowserSearch = {
     }
 
     const engine = Services.search.getEngineByName(engineName);
-    const prefName =
-      "browser.urlbar.placeholderName" + (isPrivate ? ".private" : "");
-    if (engine.isAppProvided) {
-      Services.prefs.setStringPref(prefName, engineName);
-    } else {
-      Services.prefs.clearUserPref(prefName);
+    if (!engine.isAppProvided) {
       // Set the engine name to an empty string for non-default engines, which'll
       // make sure we display the default placeholder string.
       engineName = "";

browser/components/search/SearchUIUtils.sys.mjs

@@ -15,6 +15,27 @@ XPCOMUtils.defineLazyGetter(lazy, "SearchUIUtilsL10n", () => {
 });
 
 export var SearchUIUtils = {
+  initialized: false,
+
+  init() {
+    if (!this.initialized) {
+      Services.obs.addObserver(this, "browser-search-engine-modified");
+
+      this.initialized = true;
+    }
+  },
+
+  observe(engine, topic, data) {
+    switch (data) {
+      case "engine-default":
+        this.updatePlaceholderNamePreference(engine, false);
+        break;
+      case "engine-default-private":
+        this.updatePlaceholderNamePreference(engine, true);
+        break;
+    }
+  },
+
   /**
    * Adds an open search engine and handles error UI.
    *
@@ -82,4 +103,20 @@ export var SearchUIUtils = {
       "browser.search.searchEnginesURL"
     );
   },
+
+  /**
+   * Update the placeholderName preference for the default search engine.
+   *
+   * @param {SearchEngine} engine The new default search engine.
+   * @param {boolean} isPrivate Whether this change applies to private windows.
+   */
+  updatePlaceholderNamePreference(engine, isPrivate) {
+    const prefName =
+      "browser.urlbar.placeholderName" + (isPrivate ? ".private" : "");
+    if (engine.isAppProvided) {
+      Services.prefs.setStringPref(prefName, engine.name);
+    } else {
+      Services.prefs.clearUserPref(prefName);
+    }
+  },
 };

browser/components/urlbar/tests/browser/browser_placeholder.js

@@ -253,6 +253,24 @@ add_task(async function test_private_window_separate_engine() {
   Assert.equal(win.gURLBar.placeholder, expectedString);
 
   await BrowserTestUtils.closeWindow(win);
+
+  // Verify that the placeholder for private windows is updated even when no
+  // private window is visible (https://bugzilla.mozilla.org/1792816).
+  await Services.search.setDefault(
+    originalEngine,
+    Ci.nsISearchService.CHANGE_REASON_UNKNOWN
+  );
+  await Services.search.setDefaultPrivate(
+    extraPrivateEngine,
+    Ci.nsISearchService.CHANGE_REASON_UNKNOWN
+  );
+  const win2 = await BrowserTestUtils.openNewBrowserWindow({ private: true });
+  Assert.equal(win2.gURLBar.placeholder, noEngineString);
+  await BrowserTestUtils.closeWindow(win2);
+
+  // And ensure this doesn't affect the placeholder for non private windows.
+  tabs.push(await BrowserTestUtils.openNewForegroundTab(gBrowser));
+  Assert.equal(win.gURLBar.placeholder, expectedString);
 });
 
 add_task(async function test_search_mode_engine_web() {