Setting of Upload-Length with empty PATCH request?

[nh2]

Hi, I noticed this:

tus.py/tus.py

Lines 245 to 246 in 73437c8

	headers['Upload-Length'] = str(offset)
	_upload_chunk('', offset, file_endpoint, headers=headers)

Here, an empty sequence of bytes is uploaded, and the Upload-Length header is added to a PATCH request.

This usage of setting Upload-Length for PATCH isn't mentioned in the TUS spec (https://tus.io/protocols/resumable-upload.html); the only use of Upload-Length mentioned in the core protocol is in the server's response to the HEAD request, and in protocol extensions (which aren't about PATCH).

So I wanted to ask if that was intentional, and if yes, what effect it has. Are you using it to signal to some server (which one) that no more PATCHes will follow?

It seems the change was added here: 522bda4#diff-c3f5c01a348e29bf07085b011c57af115f1d1da912541d97d57db0783dad43b0R224

[nh2]

Looking more into it, I suspect this code is intended to implement the Upload-Defer-Length part of the spec in the Creation extension:

Once it is known the Client MUST set the Upload-Length header in the next PATCH request.

So that makes sense.