lsp: Support partial result for workspace/diagnostic

[4teapo]

Zed currently does not support partial result for workspace/diagnostic, which can lead to language servers responding with all the workspace diagnostics on every such request. This may takes a lot of time to process. With partial results, the language server would first send a large chunk of diagnostics for the entire workspace, but would only send what actually changed on subsequent updates, which can take the delay from seconds to a small fraction of a second.

[SomeoneToIgnore]

Are you aware of any language server that actually implements this?
Would be amazing to work on this using a real example.

So far, seems that Zed has to

• generate a partial result token and pass it into

  zed/crates/project/src/lsp_store.rs

  Line 11415 in 01295aa

  partial_result_params: Default::default(),

  each time a diagnostics refresh is needed
• extend the code around

  zed/crates/project/src/lsp_store.rs

  Lines 11437 to 11438 in 01295aa

  	let workspace_diagnostics =
  	GetDocumentDiagnostics::deserialize_workspace_diagnostics_report(pulled_diagnostics, server.server_id());

  to understand whether we have received a partial response or not
• adjust the loop logic to continue pulling with the new partial result token until a new diagnostics refresh is called or non-partial response is returned by the server.
• adjust the diagnostics merging logic: we seem to collect the result IDs properly already, so only the old diagnostics cleanup is affected

Does not seem hard unless I miss something.

[4teapo]

luau-lsp is an example. See #33980. Also partial results go through $/progress

[4teapo]

Closed by #34022