[BUG] Regression in 1.27 for ESM file extensions

Context:

• Playwright Version: 1.27.1
• Operating System: macOS
• Node.js version: 18.10
• Browser: N/A
• Extra: N/A

Code Snippet

Trying to import test-utils.ts in a Playwright test:

// App.test.ts
import { setupTest } from './test-utils.js';

// Error: Cannot find module './test-utils.js'

Describe the bug

When trying to import .ts files, ESM requires an extension. This was working in version 1.26. However, when upgrading to 1.27, the “Cannot find module” error occurs. Downgrading back to 1.26 again fixes the problem and the file is imported just fine.

Worth highlighting that test-utils.ts (TypeScript) is the extension, not .js, but following convention .js is preferred.

Also worth noting that my repo is not "type": "module" which may be causing an issue (but we are using ESM throughout and are using "module": "ESNext" in TSConfig).

[pavelfeldman]

Awesome, thanks, I can repro it. I just could not add 2 + 2 in your original description - now that I read it, it explains the use case very well.

// example.test.ts
import { gimmeAOne } from "./playwright-utils.js";

// playwright-utils.ts
export function gimmeAOne() {
  return 1;
}

does not work in Playwright v1.27 in non-ESM mode.

[drwpow]

Sure! I was able to create a fairly-simple repro: https://github.com/drwpow/playwright-import-repro/.

Curious if this is just something weird on my machine or if you see the error too here.