Bugfix: hide Self link in included resources when there's no registered controller for it. Before, it would use the controller URL from the current request in the Self link, which is wrong.

Author: Bart Koelman

src/JsonApiDotNetCore/Serialization/Response/LinkBuilder.cs

@@ -255,6 +255,14 @@ private bool ShouldIncludeResourceLink(LinkTypes linkType, ResourceType resource
     private string? GetLinkForResourceSelf(ResourceType resourceType, IIdentifiable resource)
     {
         string? controllerName = _controllerResourceMapping.GetControllerNameForResourceType(resourceType);
+
+        if (controllerName == null)
+        {
+            // When passing null to RenderLinkForAction, it uses the controller for the current endpoint. This is incorrect for
+            // included resources of a different resource type: it should hide their Self links when there's no controller for them.
+            return null;
+        }
+
         IDictionary<string, object?> routeValues = GetRouteValues(resource.StringId!, null);
 
         return RenderLinkForAction(controllerName, GetPrimaryControllerActionName, routeValues);

test/JsonApiDotNetCoreTests/IntegrationTests/Links/LinkInclusionTests.cs

@@ -17,6 +17,7 @@ public LinkInclusionTests(IntegrationTestContext<TestableStartup<LinksDbContext>
 
         testContext.UseController<PhotosController>();
         testContext.UseController<PhotoLocationsController>();
+        testContext.UseController<PhotoAlbumsController>();
     }
 
     [Fact]

test/JsonApiDotNetCoreTests/UnitTests/Links/LinkInclusionTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using Humanizer;
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Middleware;
 using JsonApiDotNetCore.Queries;
@@ -386,7 +387,7 @@ public ResourceType GetResourceTypeForController(Type? controllerType)
 
         public string? GetControllerNameForResourceType(ResourceType? resourceType)
         {
-            return null;
+            return resourceType == null ? null : $"{resourceType.PublicName.Pascalize()}Controller";
         }
     }