From 31a62fe6fd4b4dbf666a5a1859c991c795c5bd54 Mon Sep 17 00:00:00 2001
From: martincostello <martin@martincostello.com>
Date: Thu, 2 Apr 2020 11:15:54 +0100
Subject: [PATCH] Specify Content-Length when serializing JSON

Specify the Content-Length, as it is known, when serializing JSON using System.Text.Json for compatibility with systems that do not support chunked encoding.
---
 Refit.Tests/SerializedContentTests.cs    | 20 ++++++++++++++++++++
 Refit/SystemTextJsonContentSerializer.cs |  5 ++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Refit.Tests/SerializedContentTests.cs b/Refit.Tests/SerializedContentTests.cs
index 2477720ab..674a82dcb 100644
--- a/Refit.Tests/SerializedContentTests.cs
+++ b/Refit.Tests/SerializedContentTests.cs
@@ -146,5 +146,25 @@ public async Task StreamDeserialization_UsingSystemTextJsonContentSerializer()
             Assert.Equal(model.ShortNameForAlias, result.ShortNameForAlias);
             Assert.Equal(model.ShortNameForJsonProperty, result.ShortNameForJsonProperty);
         }
+
+        [Fact]
+        public async Task StreamDeserialization_UsingSystemTextJsonContentSerializer_SetsCorrectHeaders()
+        {
+            var model = new TestAliasObject
+            {
+                ShortNameForAlias = nameof(StreamDeserialization_UsingSystemTextJsonContentSerializer),
+                ShortNameForJsonProperty = nameof(TestAliasObject)
+            };
+
+            var serializer = new SystemTextJsonContentSerializer();
+
+            var json = await serializer.SerializeAsync(model);
+
+            Assert.NotNull(json.Headers.ContentLength);
+            Assert.True(json.Headers.ContentLength.Value > 0);
+            Assert.NotNull(json.Headers.ContentType);
+            Assert.Equal("utf-8", json.Headers.ContentType.CharSet);
+            Assert.Equal("application/json", json.Headers.ContentType.MediaType);
+        }
     }
 }
diff --git a/Refit/SystemTextJsonContentSerializer.cs b/Refit/SystemTextJsonContentSerializer.cs
index e40cf9f50..93f5efe48 100644
--- a/Refit/SystemTextJsonContentSerializer.cs
+++ b/Refit/SystemTextJsonContentSerializer.cs
@@ -44,10 +44,13 @@ public Task<HttpContent> SerializeAsync<T>(T item)
 
             JsonSerializer.Serialize(utf8JsonWriter, item, jsonSerializerOptions);
 
-            var content = new StreamContent(utf8BufferWriter.DetachStream())
+            var stream = utf8BufferWriter.DetachStream();
+
+            var content = new StreamContent(stream)
             {
                 Headers =
                 {
+                    ContentLength = stream.Length,
                     ContentType = new MediaTypeHeaderValue("application/json") { CharSet = Encoding.UTF8.WebName }
                 }
             };