From c5f8a93513c48501c24b192a987c7467d8a98608 Mon Sep 17 00:00:00 2001
From: Shadowghost <Ghost_of_Stone@web.de>
Date: Tue, 1 Sep 2026 20:47:35 +0200
Subject: Close a change batch on its own window so a library scan cannot grow
 it without bound

---
 .../EntryPoints/UserDataChangeNotifierTests.cs     | 78 ++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 tests/Jellyfin.Server.Implementations.Tests/EntryPoints/UserDataChangeNotifierTests.cs

(limited to 'tests/Jellyfin.Server.Implementations.Tests/EntryPoints/UserDataChangeNotifierTests.cs')

diff --git a/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/UserDataChangeNotifierTests.cs b/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/UserDataChangeNotifierTests.cs
new file mode 100644
index 0000000000..0274398f89
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/UserDataChangeNotifierTests.cs
@@ -0,0 +1,78 @@
+using System;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Emby.Server.Implementations.EntryPoints;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Session;
+using MediaBrowser.Model.Entities;
+using MediaBrowser.Model.Session;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.EntryPoints;
+
+public class UserDataChangeNotifierTests
+{
+    // How long a test waits for the notifier's timer callback to run. Generous: the assertions are
+    // about a batch being sent at all, not about how promptly.
+    private static readonly TimeSpan _flushTimeout = TimeSpan.FromSeconds(15);
+
+    private readonly Mock<IUserDataManager> _userDataManager = new();
+    private readonly Mock<ISessionManager> _sessionManager = new();
+    private readonly Mock<IUserManager> _userManager = new();
+
+    private int _flushCount;
+
+    public UserDataChangeNotifierTests()
+    {
+        _sessionManager
+            .Setup(e => e.SendMessageToUserSessions(
+                It.IsAny<System.Collections.Generic.List<Guid>>(),
+                SessionMessageType.UserDataChanged,
+                It.IsAny<Func<UserDataChangeInfo>>(),
+                It.IsAny<CancellationToken>()))
+            .Callback(() => Interlocked.Increment(ref _flushCount))
+            .Returns(Task.CompletedTask);
+    }
+
+    [Fact]
+    public async Task OnUserDataSaved_ChangesNeverPause_StillSendsOnTheWindow()
+    {
+        // A scan changes user data continuously. The window must run from the first change of a batch,
+        // or the batch never closes and holds every item it named alive for the length of the scan.
+        var notifier = CreateNotifier();
+        await notifier.StartAsync(TestContext.Current.CancellationToken);
+
+        var userId = Guid.NewGuid();
+        var stopwatch = Stopwatch.StartNew();
+        while (stopwatch.Elapsed < _flushTimeout && Volatile.Read(ref _flushCount) == 0)
+        {
+            // Well below the window, and well below the size cap over the whole loop.
+            RaiseUserDataSaved(userId);
+            await Task.Delay(25, TestContext.Current.CancellationToken);
+        }
+
+        Assert.True(Volatile.Read(ref _flushCount) > 0, "The batch was never sent while changes kept arriving.");
+
+        await notifier.StopAsync(TestContext.Current.CancellationToken);
+        notifier.Dispose();
+    }
+
+    private UserDataChangeNotifier CreateNotifier()
+        => new(_userDataManager.Object, _sessionManager.Object, _userManager.Object);
+
+    // A folder needs none of BaseItem's static services, and PlaybackProgress is the one reason the
+    // notifier ignores outright.
+    private void RaiseUserDataSaved(Guid userId)
+        => _userDataManager.Raise(
+            e => e.UserDataSaved += null,
+            _userDataManager.Object,
+            new UserDataSaveEventArgs
+            {
+                UserId = userId,
+                SaveReason = UserDataSaveReason.UpdateUserRating,
+                Item = new Folder { Id = Guid.NewGuid() }
+            });
+}
-- 
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