Add a way to tell a rls build was successful

[alexheretic]

If a client could tell the latest Rls build had been successful they could do things like clear any build error notifications "Try running cargo check..." for that project.

Currently failing bulids & successful builds both send the same rustDocument/diagnosticsEnd. Is there a way to tell the build worked, or could we add one?

[nrc]

Yeah, it would be easy to add a field to diagnosticsEnd. Just got to be a bit careful about success means - there are builds which crash, builds which fail because of a dep (which is a 'success' for Cargo but an error condition for the RLS), builds which fail to compile but are otherwise fine, and builds which build with no errors (and of course there are warnings too).

[Xanewok]

Just a drive-by comment:
While we’re at the topic of augmenting diagnosticsEnd message, could you take a look at #653? It should introduce more general (as in less RLS-specific extensions) mechanism, replacing old messages and it has waited in the PR queue for quite a bit.

Maybe it could also report additional data on finished progress (think error code/status)?

[alexheretic]

Yep makes sense to add the functionality to/after #653, it would be cool to see that merged. What's blocking this pr at the moment, the comments seem pretty positive?

We could add a enum (string in message) readable status code for the possible outcome categories of a finished build. For the purposes of the client functionality I'm after I only need failed/working distinction. So we can just add the outcome categories that make sense now and make it more fine grained later if need be.

[alexheretic]

After implementing the window/progress messages in ide-rust I don't see a nice way of using them for this according to the proposed spec. We'd have to shove in a custom field.

It seems better to send a custom message rather than a non-standard field. Something like a rustDocument/buildFinished with { result: "success" } / { result: "build-error" } / ...

What do you guys think?

[nrc]

ISTM that the progress messages should include this info - they indicate when a build finished, so it makes sense to indicate how the build finished too (more practically, I don't think you'd ever want one message without the other, which signals to me that it should be one message). I think we should be able to influence the proposed spec still to fix this.

@Xanewok thoughts?

[Xanewok]

I agree that having a custom separate message only to indicate result of a build would be an overkill - if we're sending a message reporting progress, it makes sense to also include more details/result to the final message (containing "done": true).

I think we could leverage ResponseError and include error?: ResponseError<any>; in the window/progress message. It'd be still compliant with the original extension proposal (we only extend it with an optional field) but clients could ignore what's inside the error.

[alexheretic]

I think we could leverage ResponseError and include error?: ResponseError; in the window/progress message

Ok that sounds like it should work well, seems a reasonable thing to include in the standard too.