Multipart test failing in .NET Core

[tmenier]

RealHttpTests.can_post_multipart recently started failing in .NET Core. Since no code had changed related to this, I figured something must be broken with httpbin. But why only with .NET Core? I opened up Fiddler and had a look at the requests. The difference is immediately clear from the request headers:

Full framework:

Content-Type: multipart/form-data; boundary="3f77156c-5238-4535-a738-f1811a21ba3a"
Host: httpbin.org
Content-Length: 735
Expect: 100-continue
Connection: Keep-Alive

.NET Core:

Content-Type: multipart/form-data; boundary="4a27011b-63be-4176-a8d6-97f94166adf6"
Host: httpbin.org
Connection: Keep-Alive
Transfer-Encoding: chunked
Accept-Encoding: gzip, deflate

Aha! The .NET Core version is doing chunked encoding, the handling of which is indeed a recent regression bug with httpbin. I'm not sure why the 2 versions of HttpClient behave differently in this regard, but I figured turning off chunked encoding just for this test should at least work around the httpbin bug. But I haven't been able to figure out how to do that. Even if I set HttpRequestMessage.Headers.TransferEncodingChunked to false immediately before SendAsync of the inner handler is called, it doesn't stick. Something deep down in HttpClientHandler is apparently deciding to chunk the request. You can see this by setting a breakpoint anywhere after the request is sent and observing that TransferEncodingChunked has been set to true.

@kroniak I know you're working on changes for the next major version where we'll be targeting 1.1 and above only. Wondering if you can verify whether this chunking behavior still exists in 1.1, or if you have any other suggestions on what to do here?

[kroniak]

Work on #176 stops because nuget does not add PCL parget to final package. I am waiting. And I will see to this issue.

[kroniak]

I will continue working on issue.

[tmenier]

I think I found where TransferEncodingChunked is turned on:

https://github.com/dotnet/corefx/blob/1f77137ecb1958fe961f1d3b324ec8e2bbcd73c5/src/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpHandler.cs#L588-L594

From there I was able to disable chunking and fix the test by setting the content-length header explicitly.

@kroniak Don't worry about this one - I don't think .NET Core is doing anything wrong here, and in fact the behavior is probably a good enhancement, so I doubt they'll revert it in a newer version. The real problem is a bug in library that httpbin depends on. Once that's fixed, I'll undo the above commit. It's probably good for a chunked upload to get tested anyway. I think they're just waiting on this PR to get merged.

[tmenier]

Appears to be working on httpbin now without my hack.