Improves performance and reduce allocations in DefaultEndpointDataSource (#882)

src/Microsoft.AspNetCore.Routing/DefaultEndpointDataSource.cs

@@ -14,15 +14,20 @@ namespace Microsoft.AspNetCore.Routing
     /// </summary>
     public sealed class DefaultEndpointDataSource : EndpointDataSource
     {
-        private readonly List<Endpoint> _endpoints;
+        private readonly IReadOnlyList<Endpoint> _endpoints;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="DefaultEndpointDataSource" /> class.
         /// </summary>
         /// <param name="endpoints">The <see cref="Endpoint"/> instances that the data source will return.</param>
         public DefaultEndpointDataSource(params Endpoint[] endpoints)
-            : this((IEnumerable<Endpoint>) endpoints)
         {
+            if (endpoints == null)
+            {
+                throw new ArgumentNullException(nameof(endpoints));
+            }
+
+            _endpoints = (Endpoint[])endpoints.Clone();
         }
 
         /// <summary>
@@ -36,8 +41,7 @@ namespace Microsoft.AspNetCore.Routing
                 throw new ArgumentNullException(nameof(endpoints));
             }
 
-            _endpoints = new List<Endpoint>();
+            _endpoints = new List<Endpoint>(endpoints);
-            _endpoints.AddRange(endpoints);
         }
 
         /// <summary>

test/Microsoft.AspNetCore.Routing.Tests/DefaultEndpointDataSourceTests.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Text;
 using Microsoft.AspNetCore.Http;
 using Xunit;
 
@@ -26,6 +25,34 @@ namespace Microsoft.AspNetCore.Routing
                 endpoint => Assert.Equal("2", endpoint.DisplayName));
         }
 
+        [Fact]
+        public void Constructor_Params_ShouldMakeCopyOfEndpoints()
+        {
+            // Arrange
+            var endpoint1 = new Endpoint(TestConstants.EmptyRequestDelegate, EndpointMetadataCollection.Empty, "1");
+            var endpoint2 = new Endpoint(TestConstants.EmptyRequestDelegate, EndpointMetadataCollection.Empty, "2");
+            var endpoints = new[] { endpoint1, endpoint2 };
+
+            // Act
+            var dataSource = new DefaultEndpointDataSource(endpoints);
+            Array.Resize(ref endpoints, 1);
+            endpoints[0] = null;
+
+            // Assert
+            Assert.Equal(2, dataSource.Endpoints.Count);
+            Assert.Contains(endpoint1, dataSource.Endpoints);
+            Assert.Contains(endpoint2, dataSource.Endpoints);
+        }
+
+        [Fact]
+        public void Constructor_Params_ShouldThrowArgumentNullExceptionWhenEndpointsIsNull()
+        {
+            Endpoint[] endpoints = null;
+
+            var actual = Assert.Throws<ArgumentNullException>(() => new DefaultEndpointDataSource(endpoints));
+            Assert.Equal("endpoints", actual.ParamName);
+        }
+
         [Fact]
         public void Constructor_Enumerable_EndpointsInitialized()
         {
@@ -41,5 +68,33 @@ namespace Microsoft.AspNetCore.Routing
                 endpoint => Assert.Equal("1", endpoint.DisplayName),
                 endpoint => Assert.Equal("2", endpoint.DisplayName));
         }
+
+        [Fact]
+        public void Constructor_Enumerable_ShouldMakeCopyOfEndpoints()
+        {
+            // Arrange
+            var endpoint1 = new Endpoint(TestConstants.EmptyRequestDelegate, EndpointMetadataCollection.Empty, "1");
+            var endpoint2 = new Endpoint(TestConstants.EmptyRequestDelegate, EndpointMetadataCollection.Empty, "2");
+            var endpoints = new List<Endpoint> { endpoint1, endpoint2 };
+
+            // Act
+            var dataSource = new DefaultEndpointDataSource((IEnumerable<Endpoint>)endpoints);
+            endpoints.RemoveAt(0);
+            endpoints[0] = null;
+
+            // Assert
+            Assert.Equal(2, dataSource.Endpoints.Count);
+            Assert.Contains(endpoint1, dataSource.Endpoints);
+            Assert.Contains(endpoint2, dataSource.Endpoints);
+        }
+
+        [Fact]
+        public void Constructor_Enumerable_ShouldThrowArgumentNullExceptionWhenEndpointsIsNull()
+        {
+            IEnumerable<Endpoint> endpoints = null;
+
+            var actual = Assert.Throws<ArgumentNullException>(() => new DefaultEndpointDataSource(endpoints));
+            Assert.Equal("endpoints", actual.ParamName);
+        }
     }
 }