notifications: Add support for None option in Notification sound.

This commit adds support for a `None` option in the dropdown menu
of `Notification sound`. When this option is selected, no audible
notification is sent to the user.

`None` will appear as the first option in the dropdown menu, since
this is not categorized as a playable audio.

This new option is added so that folks can disable audio notifications
without losing their other notification configuration (like for PMs, mentions).

Necessary test case is added for this new option.

Fixes #16090.

frontend_tests/node_tests/notifications.js

@@ -59,6 +59,7 @@ function test(label, f) {
         page_params.enable_desktop_notifications = true;
         page_params.enable_sounds = true;
         page_params.wildcard_mentions_notify = true;
+        page_params.notification_sound = "ding";
         f(override);
     });
 }
@@ -239,13 +240,35 @@ test("message_is_notifiable", () => {
     assert.equal(notifications.should_send_audible_notification(message), true);
     assert.equal(notifications.message_is_notifiable(message), false);
 
+    // Case 9: If `None` is selected as the notification sound, send no
+    // audible notification, no matter what other user configurations are.
+    message = {
+        id: 50,
+        content: "message number 7",
+        sent_by_me: false,
+        notification_sent: false,
+        mentioned: true,
+        mentioned_me_directly: true,
+        type: "stream",
+        stream: "general",
+        stream_id: general.stream_id,
+        topic: "whatever",
+    };
+    page_params.notification_sound = "none";
+    assert.equal(notifications.should_send_desktop_notification(message), true);
+    assert.equal(notifications.should_send_audible_notification(message), false);
+    assert.equal(notifications.message_is_notifiable(message), true);
+
+    // Reset state
+    page_params.notification_sound = "ding";
+
     // If none of the above cases apply
     // (ie: topic is not muted, message does not mention user,
     //  no notification sent before, message not sent by user),
     // return true to pass it to notifications settings, which will return false.
     message = {
         id: 60,
-        content: "message number 7",
+        content: "message number 8",
         sent_by_me: false,
         notification_sent: false,
         mentioned: false,

static/js/notifications.js

@@ -91,14 +91,16 @@ export function initialize() {
 }
 
 function update_notification_sound_source() {
-    const audio_file_without_extension =
-        "/static/audio/notification_sounds/" + page_params.notification_sound;
+    const notification_sound = page_params.notification_sound;
+    const audio_file_without_extension = "/static/audio/notification_sounds/" + notification_sound;
     $("#notification-sound-source-ogg").attr("src", `${audio_file_without_extension}.ogg`);
     $("#notification-sound-source-mp3").attr("src", `${audio_file_without_extension}.mp3`);
 
-    // Load it so that it is ready to be played; without this the old sound
-    // is played.
-    $("#notification-sound-audio")[0].load();
+    if (notification_sound !== "none") {
+        // Load it so that it is ready to be played; without this the old sound
+        // is played.
+        $("#notification-sound-audio")[0].load();
+    }
 }
 
 export function permission_state() {
@@ -415,6 +417,12 @@ export function should_send_desktop_notification(message) {
 }
 
 export function should_send_audible_notification(message) {
+    // If `None` is selected as the notification sound, never send
+    // audible notifications regardless of other configuration.
+    if (page_params.notification_sound === "none") {
+        return false;
+    }
+
     // For streams, ding if sounds are enabled for all messages on
     // this stream.
     if (

static/js/settings_notifications.js

@@ -92,7 +92,9 @@ export function set_up() {
     });
 
     $("#play_notification_sound").on("click", () => {
-        $("#notification-sound-audio")[0].play();
+        if (page_params.notification_sound !== "none") {
+            $("#notification-sound-audio")[0].play();
+        }
     });
 
     const notification_sound_dropdown = $("#notification_sound");

static/templates/settings/notification_settings.hbs

@@ -69,6 +69,7 @@
                   {{#unless enable_sound_select}}
                   disabled
                   {{/unless}}>
+                    <option value="none">{{t "None" }}</option>
                     {{#each page_params.available_notification_sounds}}
                     <option value="{{ this }}">{{ this }}</option>
                     {{/each}}

zerver/views/user_settings.py

@@ -272,6 +272,7 @@ def json_change_notify_settings(
     if (
         notification_sound is not None
         and notification_sound not in get_available_notification_sounds()
+        and notification_sound != "none"
     ):
         raise JsonableError(_("Invalid notification sound '{}'").format(notification_sound))