Populate ActionDescriptor EndpointMetadata

Populate the EndpointMetadata property of the ActionDescriptor on
ActionDescriptor instances for minimal actions so that the attributes
associated with the request delegate can be inspected.
Relates to #34061.

Author: martincostello

src/Http/Http.Abstractions/src/Routing/EndpointMetadataCollection.cs

@@ -151,8 +151,10 @@ private T[] GetOrderedMetadataSlow<T>() where T : class
         /// </summary>
         public struct Enumerator : IEnumerator<object?>
         {
+#pragma warning disable IDE0044
             // Intentionally not readonly to prevent defensive struct copies
             private object[] _items;
+#pragma warning restore IDE0044
             private int _index;
 
             internal Enumerator(EndpointMetadataCollection collection)

src/Mvc/Mvc.ApiExplorer/src/EndpointMetadataApiDescriptionProvider.cs

@@ -121,6 +121,8 @@ private ApiDescription CreateApiDescription(RouteEndpoint routeEndpoint, string
             AddSupportedRequestFormats(apiDescription.SupportedRequestFormats, hasJsonBody, routeEndpoint.Metadata);
             AddSupportedResponseTypes(apiDescription.SupportedResponseTypes, methodInfo.ReturnType, routeEndpoint.Metadata);
 
+            AddActionDescriptorEndpointMetadata(apiDescription.ActionDescriptor, routeEndpoint.Metadata);
+
             return apiDescription;
         }
 
@@ -335,6 +337,31 @@ private static void AddResponseContentTypes(IList<ApiResponseFormat> apiResponse
             }
         }
 
+        private static void AddActionDescriptorEndpointMetadata(
+            ActionDescriptor actionDescriptor,
+            EndpointMetadataCollection endpointMetadata)
+        {
+            if (endpointMetadata.Count > 0)
+            {
+                // ActionDescriptor.EndpointMetadata is an empty array by
+                // default so need to add the metadata into a new list.
+                var metadata = new List<object>(endpointMetadata.Count);
+
+                foreach (var item in endpointMetadata)
+                {
+                    if (item is not null)
+                    {
+                        metadata.Add(item);
+                    }
+                }
+
+                if (metadata.Count > 0)
+                {
+                    actionDescriptor.EndpointMetadata = metadata;
+                }
+            }
+        }
+
         // The CompilerGeneratedAttribute doesn't always get added so we also check if the type name starts with "<"
         // For example,w "<>c" is a "declaring" type the C# compiler will generate without the attribute for a top-level lambda
         // REVIEW: Is there a better way to do this?

src/Mvc/Mvc.ApiExplorer/test/EndpointMetadataApiDescriptionProviderTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
@@ -310,6 +311,21 @@ public void AddsDisplayNameFromRouteEndpoint()
             Assert.Equal("FOO", apiDescription.ActionDescriptor.DisplayName);
         }
 
+        [Fact]
+        public void AddsMetadataFromRouteEndpoint()
+        {
+            var apiDescription = GetApiDescription([ApiExplorerSettings(IgnoreApi = true)]() => { });
+
+            Assert.NotEmpty(apiDescription.ActionDescriptor.EndpointMetadata);
+
+            var apiExplorerSettings = apiDescription.ActionDescriptor.EndpointMetadata
+                .OfType<ApiExplorerSettingsAttribute>()
+                .FirstOrDefault();
+
+            Assert.NotNull(apiExplorerSettings);
+            Assert.True(apiExplorerSettings.IgnoreApi);
+        }
+
         private IList<ApiDescription> GetApiDescriptions(
             Delegate action,
             string pattern = null,
@@ -367,7 +383,7 @@ private class ServiceProviderIsService : IServiceProviderIsService
         {
             public bool IsService(Type serviceType) => serviceType == typeof(IInferredServiceInterface);
         }
- 
+
         private class HostEnvironment : IHostEnvironment
         {
             public string EnvironmentName { get; set; }