Document diagnostics report not used when text document closed

Using language client 8.0.2-next.5. The server supports pull document diagnostics, but not workspace diagnostics.

The client (correctly) sends textDocument/diagnostic to pull a new report when a file is closed (i.e., is no longer managed). However, the returned report by the server is not then used by the client - the old diagnostics still remain.

In my case, I want to clear the diagnostics of some files when they are closed / no longer managed, but this does not happen.

Minimal example: https://github.com/JohnnyMorganz/pull-diagnostics-bug

[aeschli]

@JohnnyMorganz You should looking into using workspace diagnostics

• Workspace diagnostics are shown for all resources, unless the ones open in an editor
• Document diagnostics are shown for the resources in open editors. Your workspace diagnostics would not contain diagnostics for ignored resources, but the your document diagnostics would.

[JohnnyMorganz]

Understandable that the client should be controlling when it shows diagnostics. I guess my main ask would be is there any way of controlling this as a user, not necessarily as a server?

I feel like its quite important, as a user, that some diagnostics should be made available even when the file is closed (https://github.com/microsoft/vscode/issues/13953 shows the importance of this for js/ts), whilst other files can be ignored. It seems that this is something wanted by other servers too (https://github.com/microsoft/vscode-languageserver-node/issues/848#issuecomment-652858418), where there are cases for errors to only be shown whilst a file is open for some (not necessarily all) files

Maybe this is out of scope for this repository/issue though. Its probably also possible to control this once we implement workspace diagnostics, unless that is also not really recommended there.

EDIT: maybe this could be something configurable by a predicate in DiagnosticPullOptions on the client? e.g. as an extension to filter(document, mode), further including some sort of info about the state (open/closed)