fix(327): validate playlist name on rename (reject empty/whitespace/too-long)

fixes #327

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ErsatzTV.Application/MediaCollections/Commands/ReplacePlaylistItemsHandler.cs

@@ -74,7 +74,12 @@ public class ReplacePlaylistItemsHandler(IDbContextFactory<TvContext> dbContextF
         CancellationToken cancellationToken) =>
         PlaylistMustExist(dbContext, request.PlaylistId, cancellationToken)
             .BindT(playlist => CollectionTypesMustBeValid(request, playlist))
-            .BindT(playlist => PlaybackOrdersMustBeSupported(request, playlist));
+            .BindT(playlist => PlaybackOrdersMustBeSupported(request, playlist))
+            .BindT(playlist => ValidateName(request).Map(_ => playlist));
+
+    private static Validation<BaseError, string> ValidateName(ReplacePlaylistItems request) =>
+        request.NotEmpty(x => x.Name)
+            .Bind(_ => request.NotLongerThan(50)(x => x.Name));
 
     private static Validation<BaseError, Playlist> PlaybackOrdersMustBeSupported(
         ReplacePlaylistItems request,

ErsatzTV.Tests/Application/MediaCollections/ReplacePlaylistItemsHandlerNameValidationTests.cs

@@ -0,0 +1,120 @@
+using ErsatzTV.Application;
+using ErsatzTV.Application.MediaCollections;
+using ErsatzTV.Core;
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Infrastructure.Data;
+using ErsatzTV.Tests.Support;
+using LanguageExt;
+using Microsoft.EntityFrameworkCore;
+using NUnit.Framework;
+using Shouldly;
+using static LanguageExt.Prelude;
+
+namespace ErsatzTV.Tests.Application.MediaCollections;
+
+/// <summary>
+///     Issue #327: ReplacePlaylistItemsHandler (playlist rename) did no name validation, so a playlist
+///     could be renamed to an empty/whitespace or over-long name even though CreatePlaylistHandler
+///     already refuses those on create. Mirrors RenamePlaylistGroupHandler's ValidateName combinator
+///     (NotEmpty + NotLongerThan(50)) so create and rename enforce the same rule.
+/// </summary>
+[TestFixture]
+public class ReplacePlaylistItemsHandlerNameValidationTests
+{
+    private InMemoryTvContext _db = null!;
+
+    [SetUp]
+    public async Task SetUp() => _db = await InMemoryTvContext.CreateAsync();
+
+    [TearDown]
+    public async Task TearDown() => await _db.DisposeAsync();
+
+    private async Task SeedPlaylistAsync()
+    {
+        await using TvContext ctx = _db.CreateContext();
+        ctx.Playlists.Add(
+            new Playlist
+            {
+                Id = 1,
+                PlaylistGroupId = 1,
+                Name = "Kids",
+                IsSystem = false,
+                Version = 1,
+                Items = new List<PlaylistItem>()
+            });
+        await ctx.SaveChangesAsync();
+    }
+
+    private static ReplacePlaylistItems Command(string name) =>
+        new(
+            1,
+            name,
+            new List<ReplacePlaylistItem>
+            {
+                new(0, CollectionType.Movie, null, null, null, 55, PlaybackOrder.Shuffle, null, false, true)
+            },
+            None);
+
+    private async Task<string> ReadNameAsync()
+    {
+        await using TvContext ctx = _db.CreateContext();
+        return await ctx.Playlists.Where(p => p.Id == 1).Select(p => p.Name).SingleAsync();
+    }
+
+    private static BaseError? LeftOrNull<T>(Either<BaseError, T> result) =>
+        result.Match<BaseError?>(Right: _ => null, Left: e => e);
+
+    [Test]
+    public async Task Empty_Name_Should_Be_Rejected_And_Not_Mutate()
+    {
+        await SeedPlaylistAsync();
+        var handler = new ReplacePlaylistItemsHandler(_db.Factory);
+
+        Either<BaseError, List<PlaylistItemViewModel>> result =
+            await handler.Handle(Command(string.Empty), CancellationToken.None);
+
+        LeftOrNull(result).ShouldNotBeNull();
+        (await ReadNameAsync()).ShouldBe("Kids");
+    }
+
+    [Test]
+    public async Task Whitespace_Name_Should_Be_Rejected_And_Not_Mutate()
+    {
+        await SeedPlaylistAsync();
+        var handler = new ReplacePlaylistItemsHandler(_db.Factory);
+
+        Either<BaseError, List<PlaylistItemViewModel>> result =
+            await handler.Handle(Command("   "), CancellationToken.None);
+
+        LeftOrNull(result).ShouldNotBeNull();
+        (await ReadNameAsync()).ShouldBe("Kids");
+    }
+
+    [Test]
+    public async Task Over_Long_Name_Should_Be_Rejected_And_Not_Mutate()
+    {
+        await SeedPlaylistAsync();
+        var handler = new ReplacePlaylistItemsHandler(_db.Factory);
+
+        string tooLong = new string('a', 51);
+        Either<BaseError, List<PlaylistItemViewModel>> result =
+            await handler.Handle(Command(tooLong), CancellationToken.None);
+
+        LeftOrNull(result).ShouldNotBeNull();
+        (await ReadNameAsync()).ShouldBe("Kids");
+    }
+
+    [Test]
+    public async Task Valid_Rename_Should_Succeed()
+    {
+        await SeedPlaylistAsync();
+        var handler = new ReplacePlaylistItemsHandler(_db.Factory);
+
+        string maxLength = new string('a', 50);
+        Either<BaseError, List<PlaylistItemViewModel>> result =
+            await handler.Handle(Command(maxLength), CancellationToken.None);
+
+        result.IsRight.ShouldBeTrue();
+        (await ReadNameAsync()).ShouldBe(maxLength);
+    }
+}