Allow multiple types to be registered for one name

Fixes: aspnet/AspNetCoredotnet/extensions#13346

In 3.0 we added validation to try and report exceptions for some common
HttClient factory usage mistakes in the registration code. Unfortunately
we blocked from legitimate usage cases.

In this case, users are blocked from associating multiple types with the
same logical 'name'.

Ex:

```C#
services.AddHttpClient("Foo").AddTypedClient<A>().AddTypedClient<B>();
```

This is useful and should be allowed because it's a good way to DRY up
configuration code.

----

This change relaxes the validation when `AddTypedClient` is called, but
not when `AddHttpClient` is called without supplying a name.

We still want to block cases like the following:

```C#
services.AddHttpClient<A.SomeClient>();
services.AddHttpClient<B.SomeClient>();
```

The type short name is used as the logical name for the client (named
options) so usage like this is always a bug.
\n\nCommit migrated from dotnet/extensions@f198c46

Author: rynowak

src/HttpClientFactory/Http/src/DependencyInjection/HttpClientBuilderExtensions.cs

@@ -323,7 +323,13 @@ public static IHttpClientBuilder AddTypedClient<TClient>(this IHttpClientBuilder
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            ReserveClient(builder, typeof(TClient), builder.Name);
+            return AddTypedClientCore<TClient>(builder, validateSingleType: false);
+        }
+
+        internal static IHttpClientBuilder AddTypedClientCore<TClient>(this IHttpClientBuilder builder, bool validateSingleType)
+            where TClient : class
+        {
+            ReserveClient(builder, typeof(TClient), builder.Name, validateSingleType);
 
             builder.Services.AddTransient<TClient>(s =>
             {
@@ -377,7 +383,14 @@ public static IHttpClientBuilder AddTypedClient<TClient, TImplementation>(this I
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            ReserveClient(builder, typeof(TClient), builder.Name);
+            return AddTypedClientCore<TClient, TImplementation>(builder, validateSingleType: false);
+        }
+
+        internal static IHttpClientBuilder AddTypedClientCore<TClient, TImplementation>(this IHttpClientBuilder builder, bool validateSingleType)
+            where TClient : class
+            where TImplementation : class, TClient
+        {
+            ReserveClient(builder, typeof(TClient), builder.Name, validateSingleType);
 
             builder.Services.AddTransient<TClient>(s =>
             {
@@ -425,7 +438,13 @@ public static IHttpClientBuilder AddTypedClient<TClient>(this IHttpClientBuilder
                 throw new ArgumentNullException(nameof(factory));
             }
 
-            ReserveClient(builder, typeof(TClient), builder.Name);
+            return AddTypedClientCore<TClient>(builder, factory, validateSingleType: false);
+        }
+
+        internal static IHttpClientBuilder AddTypedClientCore<TClient>(this IHttpClientBuilder builder, Func<HttpClient, TClient> factory, bool validateSingleType)
+            where TClient : class
+        {
+            ReserveClient(builder, typeof(TClient), builder.Name, validateSingleType);
 
             builder.Services.AddTransient<TClient>(s =>
             {
@@ -472,7 +491,23 @@ public static IHttpClientBuilder AddTypedClient<TClient>(this IHttpClientBuilder
                 throw new ArgumentNullException(nameof(factory));
             }
 
-            ReserveClient(builder, typeof(TClient), builder.Name);
+            return AddTypedClientCore<TClient>(builder, factory, validateSingleType: false);
+        }
+
+        internal static IHttpClientBuilder AddTypedClientCore<TClient>(this IHttpClientBuilder builder, Func<HttpClient, IServiceProvider, TClient> factory, bool validateSingleType)
+            where TClient : class
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (factory == null)
+            {
+                throw new ArgumentNullException(nameof(factory));
+            }
+
+            ReserveClient(builder, typeof(TClient), builder.Name, validateSingleType);
 
             builder.Services.AddTransient<TClient>(s =>
             {
@@ -526,7 +561,7 @@ public static IHttpClientBuilder SetHandlerLifetime(this IHttpClientBuilder buil
         }
 
         // See comments on HttpClientMappingRegistry.
-        private static void ReserveClient(IHttpClientBuilder builder, Type type, string name)
+        private static void ReserveClient(IHttpClientBuilder builder, Type type, string name, bool validateSingleType)
         {
             var registry = (HttpClientMappingRegistry)builder.Services.Single(sd => sd.ServiceType == typeof(HttpClientMappingRegistry)).ImplementationInstance;
             Debug.Assert(registry != null);
@@ -549,6 +584,9 @@ private static void ReserveClient(IHttpClientBuilder builder, Type type, string
             // Check for same name registered to two types. This won't work because we rely on named options for the configuration.
             if (registry.NamedClientRegistrations.TryGetValue(name, out var otherType) &&
 
+                // Allow using the same name with multiple types in some cases (see callers).
+                validateSingleType &&
+
                 // Allow registering the same name twice to the same type (see above).
                 type != otherType)
             {

src/HttpClientFactory/Http/src/DependencyInjection/HttpClientFactoryServiceCollectionExtensions.cs

@@ -204,7 +204,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
 
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: true);
             return builder;
         }
 
@@ -247,7 +247,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
 
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: true);
             return builder;
         }
 
@@ -292,7 +292,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
             AddHttpClient(services);
 
             var builder = new DefaultHttpClientBuilder(services, name);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: false); // Name was explicitly provided.
             return builder;
         }
 
@@ -343,7 +343,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
             AddHttpClient(services);
 
             var builder = new DefaultHttpClientBuilder(services, name);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: false); // name was explicitly provided
             return builder;
         }
 
@@ -388,7 +388,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: true);
             return builder;
         }
 
@@ -433,7 +433,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: true);
             return builder;
         }
 
@@ -483,7 +483,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: true);
             return builder;
         }
 
@@ -533,7 +533,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
             var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: true);
             return builder;
         }
 
@@ -585,7 +585,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
 
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: false); // name was explicitly provided
             return builder;
         }
 
@@ -637,7 +637,7 @@ public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection
 
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient>();
+            builder.AddTypedClientCore<TClient>(validateSingleType: false); // name was explictly provided
             return builder;
         }
 
@@ -694,7 +694,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
 
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: false); // name was explicitly provided
             return builder;
         }
 
@@ -751,7 +751,7 @@ public static IHttpClientBuilder AddHttpClient<TClient, TImplementation>(this IS
 
             var builder = new DefaultHttpClientBuilder(services, name);
             builder.ConfigureHttpClient(configureClient);
-            builder.AddTypedClient<TClient, TImplementation>();
+            builder.AddTypedClientCore<TClient, TImplementation>(validateSingleType: false); // name was explicitly provided
             return builder;
         }
     }

src/HttpClientFactory/Http/test/DependencyInjection/HttpClientFactoryServiceCollectionExtensionsTest.cs

@@ -28,7 +28,7 @@ public void AddHttpClient_IsSelfContained_CanCreateClient()
             var serviceCollection = new ServiceCollection();
 
             // Act1
-            serviceCollection.AddHttpClient(); 
+            serviceCollection.AddHttpClient();
 
             var services = serviceCollection.BuildServiceProvider();
             var options = services.GetRequiredService<IOptionsMonitor<HttpClientFactoryOptions>>();
@@ -446,21 +446,88 @@ public void AddHttpClient_AddSameNameWithTypedClientTwice_ThrowsError()
         }
 
         [Fact]
-        public void AddHttpClient_AddSameNameWithTypedClientTwice_WithAddTypedClient_ThrowsError()
+        public void AddHttpClient_AddSameNameWithTypedClientTwice_WithAddTypedClient_IsAllowed()
         {
             // Arrange
             var serviceCollection = new ServiceCollection();
-            serviceCollection.AddHttpClient<TestTypedClient>();
+            serviceCollection.AddHttpClient<TestTypedClient>(c =>
+            {
+                c.BaseAddress = new Uri("http://example.com");
+            });
 
             // Act
-            var ex = Assert.Throws<InvalidOperationException>(() => serviceCollection.AddHttpClient("TestTypedClient").AddTypedClient<AnotherNamespace.TestTypedClient>());
+            serviceCollection.AddHttpClient("TestTypedClient").AddTypedClient<AnotherNamespace.TestTypedClient>();
+
+            var services = serviceCollection.BuildServiceProvider();
+
+            // Act
+            var client = services.GetRequiredService<TestTypedClient>();
 
             // Assert
-            Assert.Equal(
-                "The HttpClient factory already has a registered client with the name 'TestTypedClient', bound to the type 'Microsoft.Extensions.Http.TestTypedClient'. " +
-                "Client names are computed based on the type name without considering the namespace ('TestTypedClient'). " +
-                "Use an overload of AddHttpClient that accepts a string and provide a unique name to resolve the conflict.",
-                ex.Message);
+            Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
+
+            // Act
+            var client2 = services.GetRequiredService<AnotherNamespace.TestTypedClient>();
+
+            // Assert
+            Assert.Equal("http://example.com/", client2.HttpClient.BaseAddress.AbsoluteUri);
+        }
+
+        [Fact]
+        public void AddHttpClient_AddSameNameWithTypedClientTwice_WithExplicitName_IsAllowed()
+        {
+            // Arrange
+            var serviceCollection = new ServiceCollection();
+            serviceCollection.AddHttpClient<TestTypedClient>(c =>
+            {
+                c.BaseAddress = new Uri("http://example.com");
+            });
+
+            // Act
+            serviceCollection.AddHttpClient<AnotherNamespace.TestTypedClient>("TestTypedClient");
+
+            var services = serviceCollection.BuildServiceProvider();
+
+            // Act
+            var client = services.GetRequiredService<TestTypedClient>();
+
+            // Assert
+            Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
+
+            // Act
+            var client2 = services.GetRequiredService<AnotherNamespace.TestTypedClient>();
+
+            // Assert
+            Assert.Equal("http://example.com/", client2.HttpClient.BaseAddress.AbsoluteUri);
+        }
+
+        [Fact]
+        public void AddHttpClient_RegisteringMultipleTypes_WithAddTypedClient_IsAllowed()
+        {
+            // Arrange
+            var serviceCollection = new ServiceCollection();
+
+            // Act
+            serviceCollection.AddHttpClient("Test", c =>
+            {
+                c.BaseAddress = new Uri("http://example.com");
+            })
+            .AddTypedClient<TestTypedClient>()
+            .AddTypedClient<AnotherNamespace.TestTypedClient>();
+
+            var services = serviceCollection.BuildServiceProvider();
+
+            // Act
+            var client = services.GetRequiredService<TestTypedClient>();
+
+            // Assert
+            Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
+
+            // Act
+            var client2 = services.GetRequiredService<AnotherNamespace.TestTypedClient>();
+
+            // Assert
+            Assert.Equal("http://example.com/", client2.HttpClient.BaseAddress.AbsoluteUri);
         }
 
         [Fact]
@@ -475,7 +542,7 @@ public void AddHttpClient_AddTypedClient_WithServiceDelegate_ConfiguresNamedClie
             });
 
             // Act
-            serviceCollection.AddHttpClient("test").AddTypedClient<TestTypedClient>((c,s) =>
+            serviceCollection.AddHttpClient("test").AddTypedClient<TestTypedClient>((c, s) =>
             {
                 Assert.Equal("http://example.com/", c.BaseAddress.AbsoluteUri);
                 c.BaseAddress = new Uri("http://example2.com");
@@ -564,7 +631,7 @@ public void AddHttpClient_WithTypedClient_AndServiceDelegate_ConfiguresClient()
             });
 
             // Act1
-            serviceCollection.AddHttpClient<TestTypedClient>((s,c) =>
+            serviceCollection.AddHttpClient<TestTypedClient>((s, c) =>
             {
                 var options = s.GetRequiredService<IOptions<OtherTestOptions>>();
                 c.BaseAddress = new Uri(options.Value.BaseAddress);
@@ -574,7 +641,7 @@ public void AddHttpClient_WithTypedClient_AndServiceDelegate_ConfiguresClient()
 
             // Act2
             var client = services.GetRequiredService<TestTypedClient>();
-        
+
             // Assert
             Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
         }
@@ -591,7 +658,7 @@ public void AddHttpClient_WithTypedClientAndImplementation_AndServiceDelegate_Co
             });
 
             // Act1
-            serviceCollection.AddHttpClient<ITestTypedClient, TestTypedClient>((s,c) =>
+            serviceCollection.AddHttpClient<ITestTypedClient, TestTypedClient>((s, c) =>
             {
                 var options = s.GetRequiredService<IOptions<OtherTestOptions>>();
                 c.BaseAddress = new Uri(options.Value.BaseAddress);
@@ -601,7 +668,7 @@ public void AddHttpClient_WithTypedClientAndImplementation_AndServiceDelegate_Co
 
             // Act2
             var client = services.GetRequiredService<ITestTypedClient>();
-        
+
             // Assert
             Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
         }
@@ -618,7 +685,7 @@ public void AddHttpClient_WithTypedClient_AndServiceDelegate_ConfiguresNamedClie
             });
 
             // Act1
-            serviceCollection.AddHttpClient<TestTypedClient>("test", (s,c) =>
+            serviceCollection.AddHttpClient<TestTypedClient>("test", (s, c) =>
             {
                 var options = s.GetRequiredService<IOptions<OtherTestOptions>>();
                 c.BaseAddress = new Uri(options.Value.BaseAddress);
@@ -628,7 +695,7 @@ public void AddHttpClient_WithTypedClient_AndServiceDelegate_ConfiguresNamedClie
 
             // Act2
             var client = services.GetRequiredService<TestTypedClient>();
-        
+
             // Assert
             Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
         }
@@ -645,7 +712,7 @@ public void AddHttpClient_WithTypedClientAndImplementation_AndServiceDelegate_Co
             });
 
             // Act1
-            serviceCollection.AddHttpClient<ITestTypedClient, TestTypedClient>("test", (s,c) =>
+            serviceCollection.AddHttpClient<ITestTypedClient, TestTypedClient>("test", (s, c) =>
             {
                 var options = s.GetRequiredService<IOptions<OtherTestOptions>>();
                 c.BaseAddress = new Uri(options.Value.BaseAddress);
@@ -655,7 +722,7 @@ public void AddHttpClient_WithTypedClientAndImplementation_AndServiceDelegate_Co
 
             // Act2
             var client = services.GetRequiredService<ITestTypedClient>();
-        
+
             // Assert
             Assert.Equal("http://example.com/", client.HttpClient.BaseAddress.AbsoluteUri);
         }
@@ -1171,6 +1238,9 @@ public class TestTypedClient
     {
         public TestTypedClient(HttpClient httpClient)
         {
+            HttpClient = httpClient;
         }
+
+        public HttpClient HttpClient { get; }
     }
 }