Don't create non existent persons in LibraryManager.GetPerson

return null instead.

GetStudio, GetGenre, GetMusicGenre, GetYear, GetArtist still create a new one
when the requested one doesn't exist

Fixes #3901

Emby.Server.Implementations/Library/LibraryManager.cs

@@ -46,7 +46,6 @@ using MediaBrowser.Model.IO;
 using MediaBrowser.Model.Library;
 using MediaBrowser.Model.Querying;
 using MediaBrowser.Model.Tasks;
-using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
 using Episode = MediaBrowser.Controller.Entities.TV.Episode;
 using EpisodeInfo = Emby.Naming.TV.EpisodeInfo;
@@ -839,19 +838,12 @@ namespace Emby.Server.Implementations.Library
         {
             var path = Person.GetPath(name);
             var id = GetItemByNameId<Person>(path);
-            if (GetItemById(id) is not Person item)
+            if (GetItemById(id) is Person item)
             {
-                item = new Person
-                {
-                    Name = name,
-                    Id = id,
-                    DateCreated = DateTime.UtcNow,
-                    DateModified = DateTime.UtcNow,
-                    Path = path
-                };
+                return item;
             }
 
-            return item;
+            return null;
         }
 
         /// <summary>
@@ -2900,9 +2892,18 @@ namespace Emby.Server.Implementations.Library
                 var saveEntity = false;
                 var personEntity = GetPerson(person.Name);
 
-                // if PresentationUniqueKey is empty it's likely a new item.
-                if (string.IsNullOrEmpty(personEntity.PresentationUniqueKey))
+                if (personEntity is null)
                 {
+                    var path = Person.GetPath(person.Name);
+                    personEntity = new Person()
+                    {
+                        Name = person.Name,
+                        Id = GetItemByNameId<Person>(path),
+                        DateCreated = DateTime.UtcNow,
+                        DateModified = DateTime.UtcNow,
+                        Path = path
+                    };
+
                     personEntity.PresentationUniqueKey = personEntity.CreatePresentationUniqueKey();
                     saveEntity = true;
                 }

tests/Jellyfin.Server.Integration.Tests/Controllers/PersonsControllerTests.cs

@@ -0,0 +1,26 @@
+using System.Net;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Jellyfin.Server.Integration.Tests.Controllers;
+
+public class PersonsControllerTests : IClassFixture<JellyfinApplicationFactory>
+{
+    private readonly JellyfinApplicationFactory _factory;
+    private static string? _accessToken;
+
+    public PersonsControllerTests(JellyfinApplicationFactory factory)
+    {
+        _factory = factory;
+    }
+
+    [Fact]
+    public async Task GetPerson_DoesntExist_NotFound()
+    {
+        var client = _factory.CreateClient();
+        client.DefaultRequestHeaders.AddAuthHeader(_accessToken ??= await AuthHelper.CompleteStartupAsync(client));
+
+        using var response = await client.GetAsync($"Persons/DoesntExist");
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+}