Use `tsgo` to run type checks on client for watch by mjbvz · Pull Request #296215 · microsoft/vscode

mjbvz · 2026-02-19T07:14:50Z

This reduces the the first run time to get src transpiled and fully type checked to around 15seconds on my machine. Rechecking then takes around 5 seconds

This reduces the time to get `src` transpiled and fully type checked to around 15seconds on my machine

mjbvz · 2026-02-19T07:15:12Z

src/tsconfig.json

 		"allowJs": true,
 		"resolveJsonModule": true,
 		"isolatedModules": false,
+		"skipLibCheck": true,


adding this temporarily to work around microsoft/tas-client#88

Copilot

Pull request overview

Updates the development watch pipeline to use tsgo for client type-checking (in esbuild-transpile mode) to reduce end-to-end watch latency.

Changes:

Enable skipLibCheck in src/tsconfig.json to reduce type-check overhead.
Add a new watchTypeCheckTask that runs tsgo --noEmit on changes.
Switch gulp watch-client (esbuild-transpile mode) to use the new tsgo-based watcher.

Reviewed changes

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

File	Description
src/tsconfig.json	Enables `skipLibCheck` to reduce type-check cost.
build/lib/tsgo.ts	Adjusts tsgo completion/error reporting output behavior.
build/lib/compilation.ts	Introduces `watchTypeCheckTask` that debounces tsgo no-emit checks on file changes.
build/gulpfile.ts	Wires `watch-client` (esbuild mode) to use `watchTypeCheckTask` instead of the old gulp-tsb watcher.

build/lib/tsgo.ts

Copilot · 2026-02-19T07:19:32Z

build/gulpfile.ts

 const watchClientTask = useEsbuildTranspile
-	? task.define('watch-client', task.parallel(compilation.watchTask('out', false, 'src', { noEmit: true }), compilation.watchApiProposalNamesTask, compilation.watchExtensionPointNamesTask, compilation.watchCodiconsTask))
+	? task.define('watch-client', task.parallel(compilation.watchTypeCheckTask('src'), compilation.watchApiProposalNamesTask, compilation.watchExtensionPointNamesTask, compilation.watchCodiconsTask))
 	: task.define('watch-client', task.series(util.rimraf('out'), task.parallel(compilation.watchTask('out', false), compilation.watchApiProposalNamesTask, compilation.watchExtensionPointNamesTask, compilation.watchCodiconsTask)));


In esbuild-transpile mode, watch-client is now only running the tsgo typecheck watcher plus the metadata/codegen watchers. If nothing else in this task graph is generating/updating src/vs/monaco.d.ts (and related generated files) on change, that’s a regression from the previous compilation.watchTask(..., { noEmit: true }) behavior.

Either ensure watchTypeCheckTask handles Monaco d.ts generation (preferred), or add a dedicated generator watch task here.

Copilot · 2026-02-19T07:19:33Z

build/lib/compilation.ts

+export function watchTypeCheckTask(src: string): task.StreamTask {
+	const theTask = () => {
+		const projectPath = path.join(import.meta.dirname, '../../', src, 'tsconfig.json');
+		const watchInput = watch(`${src}/**`, { base: src, readDelay: 200 });
+		const tsgoStream = watchInput.pipe(util.debounce(() => {
+			const stream = createTsgoStream(projectPath, { taskName: 'watch-client-noEmit', noEmit: true });
+			const result = es.through();
+			stream.on('end', () => result.emit('end'));
+			stream.on('error', () => result.emit('end'));
+			return result;
+		}));
+		return tsgoStream;
+	};


watchTypeCheckTask replaces the old watchTask(..., { noEmit: true }) path, but it no longer runs MonacoGenerator in watch mode. That means src/vs/monaco.d.ts / standaloneEnums.ts won’t be auto-regenerated on relevant changes during gulp watch-client (esbuild mode), which previously happened via watchTask.

Consider invoking new MonacoGenerator(true).execute() (and keeping its file watchers alive) inside watchTypeCheckTask, or otherwise ensuring an equivalent Monaco d.ts generation step is still part of watch-client.

@mjbvz I think this is good feedback

build/lib/compilation.ts

jrieken · 2026-02-19T14:53:12Z

build/lib/compilation.ts

+export function watchTypeCheckTask(src: string): task.StreamTask {
+	const theTask = () => {
+		const projectPath = path.join(import.meta.dirname, '../../', src, 'tsconfig.json');
+		const watchInput = watch(`${src}/**`, { base: src, readDelay: 200 });
+		const tsgoStream = watchInput.pipe(util.debounce(() => {
+			const stream = createTsgoStream(projectPath, { taskName: 'watch-client-noEmit', noEmit: true });
+			const result = es.through();
+			stream.on('end', () => result.emit('end'));
+			stream.on('error', () => result.emit('end'));
+			return result;
+		}));
+		return tsgoStream;
+	};


@mjbvz I think this is good feedback

jrieken · 2026-02-19T14:54:47Z

build/lib/compilation.ts

+		const projectPath = path.join(import.meta.dirname, '../../', src, 'tsconfig.json');
+		const watchInput = watch(`${src}/**`, { base: src, readDelay: 200 });
+		const tsgoStream = watchInput.pipe(util.debounce(() => {
+			const stream = createTsgoStream(projectPath, { taskName: 'watch-client-noEmit', noEmit: true });


Is incremental or not? Like, will every file change cost 15 second (for type checking)?

It's closer to 5 seconds for updates. The initial 15 seconds is for the first build and is slower because all of the compile tasks are running at the same time

I've now also enabled the --incremental option to speed up recompiles. In my testing, this reduces the recheck time to 2seconds. Hopefully longer term the TS team will improve their watcher so that we can use that and speed this up even further

jrieken · 2026-02-19T14:56:00Z

build/lib/tsgo.ts

 const ansiRegex = /[\u001b\u009b][[()#;?]*(?:[0-9]{1,4}(?:;[0-9]{0,4})*)?[0-9A-ORZcf-nqry=><]/g;
 const timestampRegex = /^\[\d{2}:\d{2}:\d{2}\]\s*/;

 export function spawnTsgo(projectPath: string, config: { taskName: string; noEmit?: boolean }, onComplete?: () => Promise<void> | void): Promise<void> {


This should probably replace what I have added for CI/CD here

vscode/build/gulpfile.vscode.ts

Line 219 in 7ffca95

function runTsGoTypeCheck(): Promise<void> {

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Use tsgo to run type checks on client in watch mode

86da917

This reduces the time to get `src` transpiled and fully type checked to around 15seconds on my machine

mjbvz requested a review from jrieken February 19, 2026 07:14

mjbvz self-assigned this Feb 19, 2026

Copilot AI review requested due to automatic review settings February 19, 2026 07:14

mjbvz commented Feb 19, 2026

View reviewed changes

Copilot started reviewing on behalf of mjbvz February 19, 2026 07:15 View session

vs-code-engineering bot added this to the February 2026 milestone Feb 19, 2026

Copilot AI reviewed Feb 19, 2026

View reviewed changes

jrieken reviewed Feb 19, 2026

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mjbvz and others added 2 commits February 19, 2026 09:22

Update build/lib/compilation.ts

dbbe583

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Enable incremental builds to speed up updates after first build

cc10bc7

austindyoung mentioned this pull request Feb 26, 2026

[mirror] microsoft/vscode#296215 Use tsgo to run type checks on client for watch austindyoung/vscode-driftfence-mirror-fork#186

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mjbvz modified the milestones: February 2026, March 2026, 1.111.0, 1.112.0 Feb 26, 2026

mjbvz modified the milestones: 1.112.0, 1.113.0, 1.114.0 Mar 16, 2026

mjbvz modified the milestones: 1.114.0, 1.115.0 Mar 29, 2026

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Use `tsgo` to run type checks on client for watch#296215

Use `tsgo` to run type checks on client for watch#296215
mjbvz wants to merge 3 commits intomicrosoft:mainfrom
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mjbvz commented Feb 19, 2026 •

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Pull request overview

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mjbvz commented Feb 19, 2026 •

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