fix(language_server): don't resend diagnostic on save, when typeAware is disabled and run is onType

[yongsk0066]

Fixes an edge case introduced in #13332 where diagnostics disappear when saving a file with oxc.lint.run: "onType" and oxc.typeAware: false.

Problem

The logic from #13332 assumes tsgolint always exists when Run::OnType:

(ServerLinterRun::OnSave, Run::OnType) => (false, true)  // always run tsgolint

But when type_aware: false, there is no tsgo_linter, causing the server to return empty diagnostics instead of None, which clears all error highlights in VSCode.

Solution

Check if tsgo_linter actually exists:

(ServerLinterRun::OnSave, Run::OnType) => {
    let should_run_tsgo = self.tsgo_linter.as_ref().is_some();
    (false, should_run_tsgo)
}

Now returns None when no linters should run, preserving existing diagnostics.

Test: Added test_lint_on_run_on_type_on_save_without_type_aware with fixture

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[Copilot]

Pull Request Overview

Fixes an edge case where diagnostics would be cleared when saving a file with oxc.lint.run: "onType" and oxc.typeAware: false. The issue occurred because the logic assumed TypeScript linting was always available in onType mode, but when type awareness is disabled, no linter exists to provide diagnostics.

• Updates logic to check if TypeScript linter exists before attempting to run it on save
• Adds test coverage for the edge case scenario
• Preserves existing diagnostics when no linters should run

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
server_linter.rs	Updates the linter run logic to conditionally run TypeScript linting based on availability
on-save-no-type-aware.ts	Adds test fixture for the edge case scenario
on-save-no-type-aware.ts.snap	Snapshot test output for the new test case

---

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[Sysix]

Thank you for looking after the bug.

But when type_aware: false, there is no tsgo_linter, causing the server to return empty diagnostics instead of None, which clears all error highlights in VSCode.

My guess is, that you are still on the latest release, and not using the main language server.
This should been already fixed in #13490 with an integration test in the editor.

The lines:

oxc/crates/oxc_language_server/src/linter/server_linter.rs

Lines 356 to 361 in 78a1146

	if tsgolint && let Some(tsgo_linter) = self.tsgo_linter.as_ref() {
	self.diagnostics
	.tsgo_linter
	.pin()
	.insert(uri.to_string(), tsgo_linter.lint_file(uri, content.clone()));
	}

It will only insert it to ServerLinterDiagnostics. It will still return the oxlint diagnostics on save.

If you want to try it yourself, you can follow the instructions here:
https://oxc.rs/docs/contribute/vscode.html#building-extension-and-installing-it-locally

[yongsk0066]

Thank you for looking after the bug.

But when type_aware: false, there is no tsgo_linter, causing the server to return empty diagnostics instead of None, which clears all error highlights in VSCode.

My guess is, that you are still on the latest release, and not using the main language server. This should been already fixed in #13490 with an integration test in the editor.

The lines:

oxc/crates/oxc_language_server/src/linter/server_linter.rs

Lines 356 to 361 in 78a1146

	if tsgolint && let Some(tsgo_linter) = self.tsgo_linter.as_ref() {
	self.diagnostics
	.tsgo_linter
	.pin()
	.insert(uri.to_string(), tsgo_linter.lint_file(uri, content.clone()));
	}

It will only insert it to ServerLinterDiagnostics. It will still return the oxlint diagnostics on save.

If you want to try it yourself, you can follow the instructions here: oxc.rs/docs/contribute/vscode.html#building-extension-and-installing-it-locally

Ah, I see it was already fixed. Thanks! I'll check more carefully next time. Thanks for the review. I'll go ahead and close this PR.

[yongsk0066]

Hey @Sysix, could you review this once more? I tested and my fix also seems valid.
it takes a different approach by returning None when no linting is needed, which reduces memory usage and network calls. Would this be a viable alternative?

[Sysix]

Yes, this is optimization for onSave configuration.
If typeAware is not enabled, your MR will not send the latest (redundant) diagnostics to the client.

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13604 will not alter performance

_{Comparing yongsk0066:fix/preserve-diagnostics-ontype-save (7f6cfe2) with main (d3be692)¹}

Summary

✅ 37 untouched benchmarks

Footnotes

1. No successful run was found on main (283e127) during the generation of this report, so d3be692 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[graphite-app]

Merge activity

• Sep 11, 5:15 AM UTC: @yongsk0066 we removed the merge queue label because we could not find a Graphite account associated with your GitHub profile.

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