Delay squiggles

[Andrew Casey (amcasey)]

300ms when idle, 1500ms during active typing.
Squiggles for documents other than the one being edited refresh immediately. When the squiggle count drops to zero, refresh immediately.

Note: Does not affect computation of squiggles - only display.
Note: Doesn't affect the playground, which is deliberately bare-bones.

Caveat: Basically doesn't work without #3534 because the setTimeouts get starved.

[Copilot]

Pull request overview

This PR adds a debounced “diagnostics publisher” so the VS Code extension can delay displaying squiggles for the actively edited document (while still computing diagnostics as before), reducing churn during typing.

Changes:

• Introduces a DiagnosticsPublisher utility in the qsharp-lang npm package to debounce publishing for a single “hot” document with an idle delay and a maximum cap.
• Integrates DiagnosticsPublisher into the VS Code language-service diagnostics pipeline and tracks the “hot” document based on text-change events.
• Adds node-based unit tests for DiagnosticsPublisher and exports the new utility/types from the npm package entrypoint.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
source/vscode/src/language-service/diagnostics.ts	Wraps diagnostic publishing with DiagnosticsPublisher and tracks the hot document from VS Code edit events.
source/npm/qsharp/test/diagnosticsPublisher.test.mjs	Adds focused unit tests verifying debounce/cap/flush/dispose behavior.
source/npm/qsharp/src/main.ts	Exports DiagnosticsPublisher and DiagnosticsPublisherOptions from the public npm API.
source/npm/qsharp/src/language-service/diagnosticsPublisher.ts	Implements the debounced publisher logic (idle delay + max cap + immediate publish when cleared).

[Andrew Casey (amcasey)]

Offline copilot review found that the delays are based on diagnostic events, rather than edit events. Re-evaluating (though it seems to work well in practice).

[Andrew Casey (amcasey)]

We're reporting the same diagnostics as before, just later. The main consequence I can think of is that VS Code has some handling for stale squiggles - if you type within a squiggled span, the squiggle will expand to accommodate the new characters. We're losing that (for edits within a brief window) but the whole point of the change is to not have squiggles around the cursor while typing, so I think that's acceptable.