chore: only restart esm on Node 16+ (#12955)

packages/playwright-test/src/cli.ts

@@ -243,6 +243,10 @@ async function launchDockerContainer(): Promise<() => Promise<void>> {
 }
 
 function restartWithExperimentalTsEsm(configFile: string | null): boolean {
+  const nodeVersion = +process.versions.node.split('.')[0];
+  // New experimental loader is only supported on Node 16+.
+  if (nodeVersion < 16)
+    return false;
   if (!configFile)
     return false;
   if (process.env.PW_DISABLE_TS_ESM)

packages/playwright-test/src/loader.ts

@@ -252,8 +252,13 @@ export class Loader {
         if (didYouMean?.endsWith('.ts'))
           throw errorWithFile(file, 'Cannot import a typescript file from an esmodule.');
       }
-      if (error.code === 'ERR_UNKNOWN_FILE_EXTENSION' && error.message.includes('.ts'))
-        throw errorWithFile(file, 'Cannot import a typescript file from an esmodule.');
+      if (error.code === 'ERR_UNKNOWN_FILE_EXTENSION' && error.message.includes('.ts')) {
+        throw errorWithFile(file, `Cannot import a typescript file from an esmodule.\n${'='.repeat(80)}\nMake sure that:
+  - you are using Node.js 16+,
+  - your package.json contains "type": "module",
+  - you are using TypeScript for playwright.config.ts.
+${'='.repeat(80)}\n`);
+      }
 
       if (error instanceof SyntaxError && error.message.includes('Cannot use import statement outside a module'))
         throw errorWithFile(file, 'JavaScript files must end with .mjs to use import.');