Added MapFallback overloads that take Delegate (#34531)

- These new APIs are enlightened with the new RequestDelegateFactory and get the binding and results features that were added in .NET 6.
- Added some basic tests

Author: davidfowl

src/Http/Routing/src/Builder/MinimalActionEndpointRouteBuilderExtensions.cs

@@ -205,5 +205,86 @@ public static MinimalActionEndpointConventionBuilder Map(
 
             return new MinimalActionEndpointConventionBuilder(dataSource.AddEndpointBuilder(builder));
         }
+
+        /// <summary>
+        /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
+        /// requests for non-file-names with the lowest possible priority.
+        /// </summary>
+        /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
+        /// <param name="action">The delegate executed when the endpoint is matched.</param>
+        /// <returns>A <see cref="IEndpointConventionBuilder"/> that can be used to further customize the endpoint.</returns>
+        /// <remarks>
+        /// <para>
+        /// <see cref="MapFallback(IEndpointRouteBuilder, Delegate)"/> is intended to handle cases where URL path of
+        /// the request does not contain a file name, and no other endpoint has matched. This is convenient for routing
+        /// requests for dynamic content to a SPA framework, while also allowing requests for non-existent files to
+        /// result in an HTTP 404.
+        /// </para>
+        /// <para>
+        /// <see cref="MapFallback(IEndpointRouteBuilder, Delegate)"/> registers an endpoint using the pattern
+        /// <c>{*path:nonfile}</c>. The order of the registered endpoint will be <c>int.MaxValue</c>.
+        /// </para>
+        /// </remarks>
+        public static MinimalActionEndpointConventionBuilder MapFallback(this IEndpointRouteBuilder endpoints, Delegate action)
+        {
+            if (endpoints == null)
+            {
+                throw new ArgumentNullException(nameof(endpoints));
+            }
+
+            if (action == null)
+            {
+                throw new ArgumentNullException(nameof(action));
+            }
+
+            return endpoints.MapFallback("{*path:nonfile}", action);
+        }
+
+        /// <summary>
+        /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
+        /// the provided pattern with the lowest possible priority.
+        /// </summary>
+        /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
+        /// <param name="pattern">The route pattern.</param>
+        /// <param name="action">The delegate executed when the endpoint is matched.</param>
+        /// <returns>A <see cref="IEndpointConventionBuilder"/> that can be used to further customize the endpoint.</returns>
+        /// <remarks>
+        /// <para>
+        /// <see cref="MapFallback(IEndpointRouteBuilder, string, Delegate)"/> is intended to handle cases where no
+        /// other endpoint has matched. This is convenient for routing requests to a SPA framework.
+        /// </para>
+        /// <para>
+        /// The order of the registered endpoint will be <c>int.MaxValue</c>.
+        /// </para>
+        /// <para>
+        /// This overload will use the provided <paramref name="pattern"/> verbatim. Use the <c>:nonfile</c> route constraint
+        /// to exclude requests for static files.
+        /// </para>
+        /// </remarks>
+        public static MinimalActionEndpointConventionBuilder MapFallback(
+            this IEndpointRouteBuilder endpoints,
+            string pattern,
+            Delegate action)
+        {
+            if (endpoints == null)
+            {
+                throw new ArgumentNullException(nameof(endpoints));
+            }
+
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            if (action == null)
+            {
+                throw new ArgumentNullException(nameof(action));
+            }
+
+            var conventionBuilder = endpoints.Map(pattern, action);
+            conventionBuilder.WithDisplayName("Fallback " + pattern);
+            conventionBuilder.Add(b => ((RouteEndpointBuilder)b).Order = int.MaxValue);
+            return conventionBuilder;
+        }
     }
 }

src/Http/Routing/src/PublicAPI.Unshipped.txt

@@ -17,6 +17,8 @@ Microsoft.AspNetCore.Routing.RouteNameMetadata.RouteNameMetadata(string? routeNa
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.Map(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, Microsoft.AspNetCore.Routing.Patterns.RoutePattern! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.Map(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapDelete(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
+static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapFallback(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
+static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapFallback(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapGet(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapMethods(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Collections.Generic.IEnumerable<string!>! httpMethods, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!
 static Microsoft.AspNetCore.Builder.MinimalActionEndpointRouteBuilderExtensions.MapPost(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder! endpoints, string! pattern, System.Delegate! action) -> Microsoft.AspNetCore.Builder.MinimalActionEndpointConventionBuilder!

src/Http/Routing/test/UnitTests/Builder/MinimalActionEndpointRouteBuilderExtensionsTest.cs

@@ -183,9 +183,43 @@ public void MapDelete_BuildsEndpointWithCorrectMethod()
             Assert.Equal("/", routeEndpointBuilder.RoutePattern.RawText);
         }
 
+        [Fact]
+        public void MapFallback_BuildsEndpointWithLowestRouteOrder()
+        {
+            var builder = new DefaultEndpointRouteBuilder(new ApplicationBuilder(new EmptyServiceProvdier()));
+            _ = builder.MapFallback("/", () => { });
+
+            var dataSource = GetBuilderEndpointDataSource(builder);
+            // Trigger Endpoint build by calling getter.
+            var endpoint = Assert.Single(dataSource.Endpoints);
+
+            var routeEndpointBuilder = GetRouteEndpointBuilder(builder);
+            Assert.Equal("Fallback /", routeEndpointBuilder.DisplayName);
+            Assert.Equal("/", routeEndpointBuilder.RoutePattern.RawText);
+            Assert.Equal(int.MaxValue, routeEndpointBuilder.Order);
+        }
+
+        [Fact]
+        public void MapFallbackWithoutPath_BuildsEndpointWithLowestRouteOrder()
+        {
+            var builder = new DefaultEndpointRouteBuilder(new ApplicationBuilder(new EmptyServiceProvdier()));
+            _ = builder.MapFallback(() => { });
+
+            var dataSource = GetBuilderEndpointDataSource(builder);
+            // Trigger Endpoint build by calling getter.
+            var endpoint = Assert.Single(dataSource.Endpoints);
+
+            var routeEndpointBuilder = GetRouteEndpointBuilder(builder);
+            Assert.Equal("Fallback {*path:nonfile}", routeEndpointBuilder.DisplayName);
+            Assert.Equal("{*path:nonfile}", routeEndpointBuilder.RoutePattern.RawText);
+            Assert.Single(routeEndpointBuilder.RoutePattern.Parameters);
+            Assert.True(routeEndpointBuilder.RoutePattern.Parameters[0].IsCatchAll);
+            Assert.Equal(int.MaxValue, routeEndpointBuilder.Order);
+        }
+
         class FromRoute : Attribute, IFromRouteMetadata
         {
-            public string? Name { get; set; } 
+            public string? Name { get; set; }
         }
 
         private class HttpMethodAttribute : Attribute, IHttpMethodMetadata