Bug 1579418 - Don't reset homepage unless we need to. r=jaws

Differential Revision: https://phabricator.services.mozilla.com/D45081

--HG--
extra : moz-landing-system : lando

browser/components/preferences/in-content/home.js

@@ -323,7 +323,9 @@ var gHomePane = {
         if (startupPref.value === gMainPane.STARTUP_PREF_BLANK) {
           Services.prefs.clearUserPref(startupPref.id);
         }
+        if (HomePage.getDefault() != HomePage.getOriginalDefault()) {
           HomePage.clear();
+        }
         this._renderCustomSettings({ shouldShow: true });
         break;
     }

browser/components/preferences/in-content/tests/browser.ini

@@ -15,6 +15,7 @@ skip-if = !updater
 [browser_basic_rebuild_fonts_test.js]
 [browser_bug410900.js]
 [browser_bug731866.js]
+[browser_bug1579418.js]
 [browser_search_no_results_change_category.js]
 [browser_search_within_preferences_1.js]
 skip-if = (os == 'win' && (processor == "x86_64" || processor == "aarch64")) # Bug 1480314, aarch64 due to 1536560

browser/components/preferences/in-content/tests/browser_bug1579418.js

@@ -0,0 +1,48 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function default_homepage_test() {
+  let oldHomepagePref = Services.prefs.getCharPref("browser.startup.homepage");
+  let oldStartpagePref = Services.prefs.getIntPref("browser.startup.page");
+
+  await openPreferencesViaOpenPreferencesAPI("paneHome", { leaveOpen: true });
+
+  let doc = gBrowser.contentDocument;
+  let homeMode = doc.getElementById("homeMode");
+  let customSettings = doc.getElementById("customSettings");
+
+  // HOME_MODE_FIREFOX_HOME
+  homeMode.value = 0;
+
+  homeMode.dispatchEvent(new Event("command"));
+
+  // HOME_MODE_BLANK
+  homeMode.value = 1;
+
+  homeMode.dispatchEvent(new Event("command"));
+
+  await TestUtils.waitForCondition(
+    () => customSettings.hidden === true,
+    "Wait for customSettings to be hidden."
+  );
+
+  // HOME_MODE_CUSTOM
+  homeMode.value = 2;
+
+  homeMode.dispatchEvent(new Event("command"));
+
+  await TestUtils.waitForCondition(
+    () => customSettings.hidden === false,
+    "Wait for customSettings to be shown."
+  );
+
+  is(customSettings.hidden, false, "homePageURL should be visible");
+
+  registerCleanupFunction(async () => {
+    Services.prefs.setCharPref("browser.startup.homepage", oldHomepagePref);
+    Services.prefs.setIntPref("browser.startup.page", oldStartpagePref);
+    BrowserTestUtils.removeTab(gBrowser.selectedTab);
+  });
+});

browser/modules/HomePage.jsm

@@ -138,6 +138,14 @@ let HomePage = {
     return getHomepagePref(true);
   },
 
+  /**
+   * @returns {string}
+   *   Returns the original application homepage URL (not from prefs).
+   */
+  getOriginalDefault() {
+    return kDefaultHomePage;
+  },
+
   /**
    * @returns {boolean}
    *   Returns true if the homepage has been changed.