Set ContentLength for TestHost (#24107)

src/Hosting/TestHost/src/ClientHandler.cs

@@ -100,7 +100,7 @@ namespace Microsoft.AspNetCore.TestHost
                 if (request.Version == HttpVersion.Version20)
                 {
                     // https://tools.ietf.org/html/rfc7540
-                    req.Protocol =  HttpProtocol.Http2;
+                    req.Protocol = HttpProtocol.Http2;
                 }
                 else
                 {
@@ -142,12 +142,13 @@ namespace Microsoft.AspNetCore.TestHost
                 }
                 req.QueryString = QueryString.FromUriComponent(request.RequestUri);
 
-                if (requestContent != null)
+                // Reading the ContentLength will add it to the Headers‼
+                // https://github.com/dotnet/runtime/blob/874399ab15e47c2b4b7c6533cc37d27d47cb5242/src/libraries/System.Net.Http/src/System/Net/Http/Headers/HttpContentHeaders.cs#L68-L87
+                _ = requestContent.Headers.ContentLength;
+
+                foreach (var header in requestContent.Headers)
                 {
-                    foreach (var header in requestContent.Headers)
-                    {
-                        req.Headers.Append(header.Key, header.Value.ToArray());
-                    }
+                    req.Headers.Append(header.Key, header.Value.ToArray());
                 }
 
                 req.Body = new AsyncStreamWrapper(reader.AsStream(), () => contextBuilder.AllowSynchronousIO);

src/Hosting/TestHost/test/ClientHandlerTests.cs

@@ -4,7 +4,9 @@
 using System;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Net.Http;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
@@ -103,6 +105,51 @@ namespace Microsoft.AspNetCore.TestHost
             return httpClient.GetAsync("http://example.com");
         }
 
+        [Fact]
+        public Task ContentLengthWithBodyWorks()
+        {
+            var contentBytes = Encoding.UTF8.GetBytes("This is a content!");
+            var handler = new ClientHandler(new PathString(""), new DummyApplication(context =>
+            {
+                Assert.Equal(contentBytes.LongLength, context.Request.ContentLength);
+
+                return Task.CompletedTask;
+            }));
+            var httpClient = new HttpClient(handler);
+            var content = new ByteArrayContent(contentBytes);
+
+            return httpClient.PostAsync("http://example.com", content);
+        }
+
+        [Fact]
+        public Task ContentLengthWithNoBodyWorks()
+        {
+            var handler = new ClientHandler(new PathString(""), new DummyApplication(context =>
+            {
+                Assert.Equal(0, context.Request.ContentLength);
+
+                return Task.CompletedTask;
+            }));
+            var httpClient = new HttpClient(handler);
+
+            return httpClient.GetAsync("http://example.com");
+        }
+
+        [Fact]
+        public Task ContentLengthWithChunkedTransferEncodingWorks()
+        {
+            var handler = new ClientHandler(new PathString(""), new DummyApplication(context =>
+            {
+                Assert.Null(context.Request.ContentLength);
+
+                return Task.CompletedTask;
+            }));
+
+            var httpClient = new HttpClient(handler);
+
+            return httpClient.PostAsync("http://example.com", new UnlimitedContent());
+        }
+
         [Fact]
         public async Task ServerTrailersSetOnResponseAfterContentRead()
         {
@@ -566,5 +613,19 @@ namespace Microsoft.AspNetCore.TestHost
                 }
             }
         }
+
+        private class UnlimitedContent : HttpContent
+        {
+            protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
+            {
+                return Task.CompletedTask;
+            }
+
+            protected override bool TryComputeLength(out long length)
+            {
+                length = -1;
+                return false;
+            }
+        }
     }
 }