FIX: Maintain notification order by priority (#13186)

When the client received a new notification, it prioritized only PM
notifications instead of maintaining the priority order. Later, the
check for missing notification deleted all notifications that were
in the wrong order because it could not match the IDs.

The correct order puts high_priority AND unread notifications first.
Low priority or read notifications (including high priority, but read
notifications) come after.

app/assets/javascripts/discourse/app/initializers/subscribe-user-notifications.js

@@ -73,17 +73,19 @@ export default {
             );
 
             if (staleIndex === -1) {
-              // this gets a bit tricky, unread pms are bumped to front
+              // high priority and unread notifications are first
               let insertPosition = 0;
-              if (lastNotification.notification_type !== 6) {
-                insertPosition = oldNotifications.findIndex(
-                  (n) => n.notification_type !== 6 || n.read
+
+              if (!lastNotification.high_priority || lastNotification.read) {
+                const nextPosition = oldNotifications.findIndex(
+                  (n) => !n.high_priority || n.read
                 );
-                insertPosition =
-                  insertPosition === -1
-                    ? oldNotifications.length - 1
-                    : insertPosition;
+
+                if (nextPosition !== -1) {
+                  insertPosition = nextPosition;
+                }
               }
+
               oldNotifications.insertAt(
                 insertPosition,
                 EmberObject.create(lastNotification)

app/assets/javascripts/discourse/tests/acceptance/notifications-test.js

@@ -0,0 +1,136 @@
+import { visit } from "@ember/test-helpers";
+import {
+  acceptance,
+  publishToMessageBus,
+} from "discourse/tests/helpers/qunit-helpers";
+import { test } from "qunit";
+
+acceptance("User Notifications", function (needs) {
+  needs.user();
+
+  test("Update works correctly", async function (assert) {
+    await visit("/");
+    await click("li.current-user");
+
+    // set older notifications to read
+
+    publishToMessageBus("/notification/19", {
+      unread_notifications: 5,
+      unread_private_messages: 0,
+      unread_high_priority_notifications: 0,
+      read_first_notification: false,
+      last_notification: {},
+      recent: [
+        [123, false],
+        [456, false],
+        [789, true],
+        [1234, true],
+        [5678, true],
+      ],
+      seen_notification_id: null,
+    });
+
+    await visit("/"); // wait for re-render
+
+    assert.equal(find("#quick-access-notifications li").length, 5);
+
+    // high priority, unread notification - should be first
+
+    publishToMessageBus("/notification/19", {
+      unread_notifications: 6,
+      unread_private_messages: 0,
+      unread_high_priority_notifications: 1,
+      read_first_notification: false,
+      last_notification: {
+        notification: {
+          id: 42,
+          user_id: 1,
+          notification_type: 5,
+          high_priority: true,
+          read: false,
+          high_priority: true,
+          created_at: "2021-01-01 12:00:00 UTC",
+          post_number: 1,
+          topic_id: 42,
+          fancy_title: "First notification",
+          slug: "topic",
+          data: {
+            topic_title: "First notification",
+            original_post_id: 42,
+            original_post_type: 1,
+            original_username: "foo",
+            revision_number: null,
+            display_username: "foo",
+          },
+        },
+      },
+      recent: [
+        [42, false],
+        [123, false],
+        [456, false],
+        [789, true],
+        [1234, true],
+        [5678, true],
+      ],
+      seen_notification_id: null,
+    });
+
+    await visit("/"); // wait for re-render
+
+    assert.equal(find("#quick-access-notifications li").length, 6);
+    assert.equal(
+      find("#quick-access-notifications li span[data-topic-id]")[0].innerText,
+      "First notification"
+    );
+
+    // high priority, read notification - should be second
+
+    publishToMessageBus("/notification/19", {
+      unread_notifications: 7,
+      unread_private_messages: 0,
+      unread_high_priority_notifications: 1,
+      read_first_notification: false,
+      last_notification: {
+        notification: {
+          id: 43,
+          user_id: 1,
+          notification_type: 5,
+          high_priority: true,
+          read: true,
+          high_priority: false,
+          created_at: "2021-01-01 12:00:00 UTC",
+          post_number: 1,
+          topic_id: 42,
+          fancy_title: "Second notification",
+          slug: "topic",
+          data: {
+            topic_title: "Second notification",
+            original_post_id: 42,
+            original_post_type: 1,
+            original_username: "foo",
+            revision_number: null,
+            display_username: "foo",
+          },
+        },
+      },
+      recent: [
+        [42, false],
+        [43, true],
+        [123, false],
+        [456, false],
+        [789, true],
+        [1234, true],
+        [5678, true],
+      ],
+      seen_notification_id: null,
+    });
+
+    await visit("/"); // wait for re-render
+
+    assert.equal(find("#quick-access-notifications li").length, 7);
+    assert.equal(
+      find("#quick-access-notifications li span[data-topic-id]")[1].innerText,
+      "Second notification"
+    );
+  });
+});

app/serializers/notification_serializer.rb

@@ -7,6 +7,7 @@ class NotificationSerializer < ApplicationSerializer
              :external_id,
              :notification_type,
              :read,
+             :high_priority,
              :created_at,
              :post_number,
              :topic_id,