1 files changed, 77 insertions, 0 deletions
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Users/DisplayPreferencesManagerConcurrentCreateTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Users/DisplayPreferencesManagerConcurrentCreateTests.cs
new file mode 100644
index 0000000000..72ca680cf2
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Users/DisplayPreferencesManagerConcurrentCreateTests.cs
@@ -0,0 +1,77 @@
+using System;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Server.Implementations.Tests.Item;
+using Jellyfin.Server.Implementations.Users;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.Users;
+
+/// <summary>
+/// Two first-ever requests for the same preferences can both find nothing and both insert; the unique index lets one
+/// through. The other has to return the stored preferences instead of failing.
+/// </summary>
+public sealed class DisplayPreferencesManagerConcurrentCreateTests : SqliteDbTestFixture
+{
+    private const string Client = "client";
+
+    private static readonly Guid _userId = Guid.Parse("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa");
+    private static readonly Guid _itemId = Guid.Parse("bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb");
+
+    private readonly CompetingInsert _competingInsert;
+    private readonly DisplayPreferencesManager _manager;
+
+    public DisplayPreferencesManagerConcurrentCreateTests()
+        : this(new CompetingInsert())
+    {
+    }
+
+    private DisplayPreferencesManagerConcurrentCreateTests(CompetingInsert competingInsert)
+        : base(competingInsert)
+    {
+        _competingInsert = competingInsert;
+        _manager = new DisplayPreferencesManager(CreateDbContextFactory());
+
+        using var context = CreateDbContext();
+        context.Users.Add(new User("user", "auth-provider", "reset-provider") { Id = _userId });
+        context.SaveChanges();
+    }
+
+    [Fact]
+    public void GetDisplayPreferences_AnotherRequestStoresThemFirst_ReturnsTheStoredPreferences()
+    {
+        var storedId = 0;
+        _competingInsert.Before = () =>
+        {
+            using var context = CreateDbContext();
+            var stored = new DisplayPreferences(_userId, _itemId, Client);
+            context.DisplayPreferences.Add(stored);
+            context.SaveChanges();
+            storedId = stored.Id;
+        };
+
+        var preferences = _manager.GetDisplayPreferences(_userId, _itemId, Client);
+
+        Assert.NotEqual(0, storedId);
+        Assert.Equal(storedId, preferences.Id);
+        using var check = CreateDbContext();
+        Assert.Single(check.DisplayPreferences);
+    }
+
+    /// <summary>
+    /// Stores the other request's row just before the next save, after the manager has looked for the preferences.
+    /// </summary>
+    private sealed class CompetingInsert : SaveChangesInterceptor
+    {
+        public Action? Before { get; set; }
+
+        public override InterceptionResult<int> SavingChanges(DbContextEventData eventData, InterceptionResult<int> result)
+        {
+            // Disarmed first, because the competing save goes through this interceptor as well.
+            var before = Before;
+            Before = null;
+            before?.Invoke();
+            return result;
+        }
+    }
+}