Set 'Transfer-Encoding: chunked' if data is a file with length 0

[BraulioVM]

Fixes #2215

This is the first time I contribute to the project so I am not sure at all I put that code where it belongs. I know I have to add tests for this, but wanted to show you this beforehand.

Did I do this right?

Thank you

[Lukasa]

@BraulioVM This is a good first pass! I have a draft of this fix sitting around on my laptop, so when I get home I'll show you how I approached it and let you take the ideas you like best.

[BraulioVM]

@Lukasa Thanks!

I have just seen #2866, which won't allow me to implement the tests I want, so I might as well think of a solution for that issue.

[Lukasa]

So I think this change is not quite right. What we want is a simple change around line 437. Right now we test length for whether it is None: we should just broaden that to say if length. That way, we'll fall through to chunked encoding for zero-length files.

[BraulioVM]

I see. What I did didn't make any sense because file objects are streams. However, this change won't just affect files, it will affect any stream with length 0. Things will keep working, but I thought we just wanted to set 'Transfer-Encoding: chunked' if data was a file object with super_len(data) == 0.

[Lukasa]

@BraulioVM That's actually intentional: sending a chunked zero-length stream is fine, there won't be a problem there. That way, the code is clearer. =)

So, this change looks good to me, but I'll let @sigmavirus24 review it.

[BraulioVM]

Is there anything else I should do regarding this PR?

[Lukasa]

@BraulioVM Nope, just waiting for @sigmavirus24 to get enough time to swing by and take a look at it. =)

[sigmavirus24]

Woops! Sorry. I lost track of this with recent goings on IRL. This looks great to me! Thanks @BraulioVM