Stop setting content length 0 on 204s in MVC. (#43360)

Author: adityamandaleeka

src/Mvc/Mvc.Core/src/Formatters/HttpNoContentOutputFormatter.cs

@@ -34,7 +34,6 @@ public bool CanWriteResult(OutputFormatterCanWriteContext context)
     public Task WriteAsync(OutputFormatterWriteContext context)
     {
         var response = context.HttpContext.Response;
-        response.ContentLength = 0;
 
         if (response.StatusCode == StatusCodes.Status200OK)
         {

src/Mvc/Mvc.Core/test/Formatters/NoContentFormatterTests.cs

@@ -130,6 +130,26 @@ public async Task WriteAsync_WritesTheStatusCode204()
         Assert.Equal(StatusCodes.Status204NoContent, context.HttpContext.Response.StatusCode);
     }
 
+    [Fact]
+    public async Task WriteAsync_DoesNotHaveContentLengthSet()
+    {
+        // Arrange
+        var context = new OutputFormatterWriteContext(
+            new DefaultHttpContext(),
+            new TestHttpResponseStreamWriterFactory().CreateWriter,
+            typeof(string),
+            @object: null);
+
+        var formatter = new HttpNoContentOutputFormatter();
+
+        // Act
+        await formatter.WriteAsync(context);
+
+        // Assert
+        // No Content responses shouldn't have a Content-Length.
+        Assert.Null(context.HttpContext.Response.ContentLength);
+    }
+
     [Fact]
     public async Task WriteAsync_ContextStatusCodeSet_WritesSameStatusCode()
     {