settings: Remove default_language_name from page_params.

default_language_name was a part of page_params which is actually
redundant considering that we already have language_list and
default_language available to frontend which can be used to
get the default_language_name and hence prevents the backend
from sending an additional parameter.

Fixes part of #18673.

frontend_tests/node_tests/dispatch.js

@@ -646,6 +646,7 @@ run_test("typing", ({override}) => {
 });
 
 run_test("update_display_settings", ({override}) => {
+    settings_display.set_default_language_name = () => {};
     let event = event_fixtures.update_display_settings__default_language;
     page_params.default_language = "en";
     override(settings_display, "update_page", noop);

static/js/server_events_dispatch.js

@@ -564,7 +564,7 @@ export function dispatch_normal_event(event) {
                 // a reload is fundamentally required because we
                 // cannot rerender with the new language the strings
                 // present in the backend/Jinja2 templates.
-                page_params.default_language_name = event.language_name;
+                settings_display.set_default_language_name(event.language_name);
             }
             if (event.setting_name === "twenty_four_hour_time") {
                 // Rerender the whole message list UI

static/js/settings.js

@@ -14,6 +14,7 @@ import * as people from "./people";
 import * as settings_bots from "./settings_bots";
 import * as settings_config from "./settings_config";
 import * as settings_data from "./settings_data";
+import * as settings_display from "./settings_display";
 import * as settings_panel_menu from "./settings_panel_menu";
 import * as settings_sections from "./settings_sections";
 import * as settings_toggle from "./settings_toggle";
@@ -111,6 +112,7 @@ export function build_page() {
         user_can_change_name: settings_data.user_can_change_name(),
         user_can_change_avatar: settings_data.user_can_change_avatar(),
         user_role_text: people.get_user_type(page_params.user_id),
+        default_language_name: settings_display.default_language_name,
     });
 
     $(".settings-box").html(rendered_settings_tab);

static/js/settings_display.js

@@ -14,6 +14,22 @@ const meta = {
     loaded: false,
 };
 
+function get_default_language_name(language_code) {
+    const language_list_map = {};
+
+    // One-to-one mapping from code to name for all languages
+    for (const language of page_params.language_list) {
+        language_list_map[language.code] = language.name;
+    }
+    return language_list_map[language_code];
+}
+
+export let default_language_name;
+
+export function set_default_language_name(name) {
+    default_language_name = name;
+}
+
 function change_display_setting(data, status_element, success_msg_html, sticky) {
     const $status_el = $(status_element);
     const status_is_sticky = $status_el.data("is_sticky");
@@ -196,7 +212,7 @@ export async function report_emojiset_change() {
 
 export function update_page() {
     $("#left_side_userlist").prop("checked", page_params.left_side_userlist);
-    $("#default_language_name").text(page_params.default_language_name);
+    $("#default_language_name").text(default_language_name);
     $("#translate_emoticons").prop("checked", page_params.translate_emoticons);
     $("#twenty_four_hour_time").val(JSON.stringify(page_params.twenty_four_hour_time));
     $("#color_scheme").val(JSON.stringify(page_params.color_scheme));
@@ -205,3 +221,8 @@ export function update_page() {
     // TODO: Set emojiset selector here.
     // Longer term, we'll want to automate this function
 }
+
+export function initialize() {
+    const language_name = get_default_language_name(page_params.default_language);
+    set_default_language_name(language_name);
+}

static/js/ui_init.js

@@ -58,6 +58,7 @@ import * as search from "./search";
 import * as search_pill_widget from "./search_pill_widget";
 import * as sent_messages from "./sent_messages";
 import * as server_events from "./server_events";
+import * as settings_display from "./settings_display";
 import * as settings_panel_menu from "./settings_panel_menu";
 import * as settings_sections from "./settings_sections";
 import * as settings_toggle from "./settings_toggle";
@@ -520,6 +521,7 @@ export function initialize_everything() {
     gear_menu.initialize();
     giphy.initialize();
     presence.initialize(presence_params);
+    settings_display.initialize();
     settings_panel_menu.initialize();
     settings_sections.initialize();
     settings_toggle.initialize();

static/templates/settings/display_settings.hbs

@@ -9,7 +9,7 @@
             <div class="input-group user-name-section">
                 <label class="inline-block title">{{t "Default language" }}</label>
                 <button id="default_language" type="button" class="button btn-link rounded small inline-block">
-                    <span id="default_language_name">{{page_params.default_language_name}}</span>
+                    <span id="default_language_name">{{default_language_name}}</span>
                     <i class="fa fa-pencil"></i>
                 </button>
             </div>

zerver/lib/home.py

@@ -15,7 +15,6 @@ from zerver.lib.i18n import (
     get_and_set_request_language,
     get_language_list,
     get_language_list_for_templates,
-    get_language_name,
     get_language_translation_data,
 )
 from zerver.lib.users import compute_show_invites_and_add_streams
@@ -197,7 +196,6 @@ def build_page_params_for_home_page_load(
         # Only show marketing email settings if on Zulip Cloud
         corporate_enabled=settings.CORPORATE_ENABLED,
         ## Misc. extra data.
-        default_language_name=get_language_name(register_ret["default_language"]),
         language_list_dbl_col=get_language_list_for_templates(register_ret["default_language"]),
         language_list=get_language_list(),
         needs_tutorial=needs_tutorial,

zerver/tests/test_home.py

@@ -65,7 +65,6 @@ class HomeTest(ZulipTestCase):
         "custom_profile_field_types",
         "custom_profile_fields",
         "default_language",
-        "default_language_name",
         "default_view",
         "delivery_email",
         "demote_inactive_streams",