Panic on future cancellation

[s-panferov]

Consider this scenario: we are invoking a request,

client.send_request::<MyRequest>(params).await?;

but the future that awaits it is getting cancelled and therefore the receiving end of the channel is getting dropped. Currently this would cause a panic with the "receiver already dropped" message. I believe it's coming from here:

tx.send(r).expect("receiver already dropped");

This is quite common situation and it feels like this code should not panic. Can the send error be safely ignored instead?

[ebkalderon]

I think that's reasonable enough. The code could simply be changed to swallow the Result with a simple let _ = assignment and not expecting on it.

[peterhuene]

I'm currently hitting this issue with a textDocument/diagnostics event.

For a typical file, my server responds to this request in a few hundred microseconds. However, if I type as fast as my keyboard allows me in the document, eventually one of these requests will not complete in time for the client to cancel a previous one.

It panics with the above on trying to send the result on a closed channel.

I can submit a fix if this isn't on anyone's radar.