Handle empty body in decompression layer

[ducaale]

• I have looked for existing issues (including closed) about this

Feature Request

Ignore decompression UnexpectedEOF errors for responses with empty body

Motivation

Servers sometimes return content-encoding/content-length with empty body for HEAD requests. I was looking into refactoring reqwest's decompression to use tower-http and would like to port this functionality to tower-http::decompression.

Proposal

Add boolean flag to StreamErrorIntoIoError to track whether any data has been read. Swallow any decompression errors in WrapBody if flag is not set.

Alternatives

I have thought about having two layers before and after decompression layer. One tracks if any data has been read while the other conditionally suppresses error (inspired by ducaale/xh#411).

But before pursuing this idea any further, I wanted to see if this can be handled by tower-http instead.

[seanmonstar]

I do think it should be fixed here in tower-http. While from a code perspective, keeping it in separate layers could be cleaner, my experience in reqwest is that users expect it to just work, and it's "weird" that some server responses causes errors. So, whichever way it's implemented is fine with me, but I think users of tower_http::decompression should Just Get It, without thinking about it.

[0x676e67]

Should we properly shutdown asynchronous compression? Regarding: Nullus157/async-compression#420, here is a solution: rust-lang/docs.rs#2988