Distinguished error for client disconnection

[itowlson]

I mucked up my content length header, leaving it too short.

curl disconnected after receiving the prescribed amount of content. (Or wasi-http disconnected after serving the prescribed amount of content. Something.)

Spin got mad and told me I had a "Component error after response started."

The amount of time I spent trying to track that error down in my code.

Anyway I dunno if this is feasible but I would love it if we could provide an error saying "the client disconnected while we were still sending data." I mean, yes, there was a component error, but the message implies something like "it panicked while streaming" rather than "you mucked up your content-length you bearded twit."

[itowlson]

Although, on reflection, given that there was a Wasm backtrace associated with the error, perhaps this is a StarlingMonkey issue (as I was using the JS SDK). Anyway I'll investigate further at some point unless someone thinks "ooh I know what's going on."

[lann]

Or wasi-http disconnected after serving the prescribed amount of content.

I believe wasmtime-wasi-http will blow up if you send too much content:

https://github.com/bytecodealliance/wasmtime/blob/8801023b6896fda140f08e9a9abbfb6d1154cb48/crates/wasi-http/src/body.rs#L614-L619

[lann]

Notably that error is returned to the guest, so this is likely an SDK issue.

[vdice]

In Spin triage we thought this may be better placed in the spin-js-sdk backlog as recent comments point to it being an SDK issue.