Port experimentation service and reporting to extension by DanielRosenwasser · Pull Request #3675 · microsoft/typescript-go

DanielRosenwasser · 2026-05-01T16:54:52Z

No description provided.

DanielRosenwasser · 2026-05-01T16:55:26Z

        "@vscode/extension-telemetry": "^1.5.1",
-        "vscode-languageclient": "^10.0.0-next.21"
+        "vscode-languageclient": "^10.0.0-next.21",
+        "vscode-tas-client": "0.1.84"


Locked on 0.1.84 because of microsoft/tas-client#95

Copilot

Pull request overview

Ports VS Code TAS (experimentation) plumbing into the native-preview VS Code extension so telemetry can include shared experimentation context (flights/treatments) and the extension can query treatment variables.

Changes:

Add vscode-tas-client dependency and wire experimentation telemetry into the existing telemetry reporter.
Introduce an ExperimentationService wrapper plus a helper to read extension package name/version for TAS initialization.
Update extension activation to construct the experimentation service during startup; add a new _extension/pnpm-lock.yaml.

Show a summary per file

File	Description
package-lock.json	Adds `vscode-tas-client` (and transitive `tas-client`) to the workspace lockfile.
_extension/package.json	Declares `vscode-tas-client` dependency for the extension workspace.
_extension/pnpm-lock.yaml	Adds a pnpm lockfile for the extension workspace.
_extension/tsconfig.json	Changes TS `module` setting to `preserve` for the extension project.
_extension/src/util.ts	Adds `getPackageInfo` helper for extension id/version discovery.
_extension/src/telemetryReporting.ts	Extends the telemetry reporter to implement `IExperimentationTelemetry` and inject shared properties.
_extension/src/extension.ts	Instantiates `ExperimentationService` during activation.
_extension/src/experimentationService.ts	New TAS experimentation service wrapper and initialization logic.
_extension/src/commands.ts	Removes an unused import.

Copilot's findings

Files not reviewed (1)

_extension/pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (1)

_extension/src/experimentationService.ts:62

createTasExperimentationService awaits experimentationService.initialFetch and will reject if the fetch fails. Since ExperimentationService constructs this promise without attaching a rejection handler (and activate doesn't await it), this can trigger an unhandled promise rejection during activation. Consider catching/logging fetch errors inside createTasExperimentationService (or in the constructor) and returning a usable service that falls back gracefully.

    const experimentationService = tas.getExperimentationService(id, version, targetPopulation, reporter, globalState);
    await experimentationService.initialFetch;
    return experimentationService;

Files reviewed: 7/9 changed files
Comments generated: 4

+    public async getTreatmentVariable<K extends keyof ExperimentTypes>(name: K, defaultValue: ExperimentTypes[K]): Promise<ExperimentTypes[K]> {
+        const experimentationService = await this._experimentationServicePromise;
+        try {
+            const treatmentVariable = await experimentationService.getTreatmentVariableAsync("vscode", name, /*checkCache*/ true) as ExperimentTypes[K];
+            return treatmentVariable ?? defaultValue;
+        }
+        catch {
+            return defaultValue;
+        }


DanielRosenwasser · 2026-05-01T17:22:23Z

+    const packageInfo = getPackageInfo(context);
+    if (packageInfo) {
+        const { name: id, version } = packageInfo;
+        // Constructing the experimentation service actually sets shared properties
+        // so that events include context on treatments/flights.
+        const _expService = new ExperimentationService(telemetryReporter, id, version, context.globalState);
+    }


For now this is fine, we are just using this to stamp common properties like the assignment context. I could just void it.

This blocks actually constructing the service which basically delays extension loads. Our `getTreatmentVariable` calls `getTreatmentVariableAsync`, which calls their `getFeaturesAsync` and actually resolves the initial fetch.

jakebailey · 2026-05-01T18:05:41Z

    "compilerOptions": {
        "target": "es2023",
-        "module": "NodeNext",
+        "module": "preserve",


we bundle, so maybe this should be bundler mode?

I actually don't think I needed to make this change. I might undo it.

Though I think that preserve implies bundler, right?

we only bundle now

jakebailey · 2026-05-01T18:51:27Z


+    const packageInfo = getPackageInfo(context);
+    if (packageInfo) {
+        const { name: id, version } = packageInfo;


Not just context.extension.id?

No, name is native-preview, context.extension.id would be TypeScriptTeam.native-preview

well right, but surely the exp platform wants more of a name than native-preview?

You are right and I think that the built-in extension was doing this wrong.

Oh, yeah, because builtin extensions don't have a publisher name and that's how they are determined to be builtins

DanielRosenwasser added 2 commits April 30, 2026 23:16

Port over experimentation service & reporting.

89d6bd4

Remove unused import.

9badbce

DanielRosenwasser requested review from Copilot, jakebailey and mjbvz May 1, 2026 16:54

DanielRosenwasser commented May 1, 2026

View reviewed changes

Copilot started reviewing on behalf of DanielRosenwasser May 1, 2026 16:55 View session

Copilot AI reviewed May 1, 2026

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DanielRosenwasser added 4 commits May 1, 2026 17:20

Remove pnpm lock

3707a4c

Format.

6af08c5

Don't await initialFetch.

98b0f11

This blocks actually constructing the service which basically delays extension loads. Our `getTreatmentVariable` calls `getTreatmentVariableAsync`, which calls their `getFeaturesAsync` and actually resolves the initial fetch.

Remove unnecessary async/Promises.

3867c73

jakebailey reviewed May 1, 2026

View reviewed changes

Comment thread _extension/src/commands.ts

DanielRosenwasser added 2 commits May 1, 2026 18:39

Remove more unused code.

0a153b7

Update extension configuration.

0a1f767

jakebailey reviewed May 1, 2026

View reviewed changes

Comment thread _extension/src/experimentationService.ts Outdated

Remove mistaken copy/paste.

7f3c91d

jakebailey reviewed May 1, 2026

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DanielRosenwasser added 3 commits May 1, 2026 18:52

Format.

a6eacc9

void

fd61147

Use context.extension.id, assert on version.

2c845d5

jakebailey approved these changes May 1, 2026

View reviewed changes

DanielRosenwasser added this pull request to the merge queue May 1, 2026

Merged via the queue into main with commit 6dff52f May 1, 2026
21 checks passed

DanielRosenwasser deleted the experimentation branch May 1, 2026 23:16

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DanielRosenwasser May 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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DanielRosenwasser May 1, 2026 •

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