test(ci): smoke-test the ESM bundle under Node's native loader

The existing validate-cjs smoke test loads the bundle with require(), whose CJS
resolver tolerates extensionless subpath imports -- so it never caught the
invalid ESM output that broke Node's native loader. Add an ESM counterpart that
imports dist/es/index.mjs under the native loader and wire it into CI right
after validate-cjs.

Verified: the check passes on a healthy build and fails with ERR_MODULE_NOT_FOUND
when a .js extension is stripped from a dayjs subpath import in the built output.

Author: oliverlaz

.github/workflows/ci.yml

@@ -36,6 +36,9 @@ jobs:
       - name: Validate CJS bundle with Node ${{ env.NODE_VERSION }}
         run: yarn validate-cjs
 
+      - name: Validate ESM bundle with Node ${{ env.NODE_VERSION }}
+        run: yarn validate-esm
+
       - name: Validate translations
         run: yarn validate-translations
 

package.json

@@ -212,6 +212,7 @@
     "types:tests": "tsc --project tsconfig.test.json --noEmit",
     "validate-translations": "node scripts/validate-translations.js",
     "validate-cjs": "concurrently 'node scripts/validate-cjs-node-bundle.cjs' 'node scripts/validate-cjs-browser-bundle.cjs'",
+    "validate-esm": "node scripts/validate-esm-node-bundle.mjs",
     "semantic-release": "semantic-release",
     "prepack": "yarn build",
     "examples:build": "yarn workspaces foreach -A --include '@stream-io/stream-chat-react-*' run build",

scripts/validate-esm-node-bundle.mjs

@@ -0,0 +1,11 @@
+// ESM counterpart to validate-cjs-node-bundle.cjs.
+//
+// Node's native ESM loader is stricter than any bundler: it requires file
+// extensions on subpath imports of dependencies that ship no "exports" map
+// (e.g. `dayjs/plugin/calendar` must be written as `dayjs/plugin/calendar.js`).
+// Such specifiers resolve fine through Turbopack/Webpack/Vite but throw
+// ERR_MODULE_NOT_FOUND under Node — the same path Next.js takes when it loads
+// this package as a server external. Importing the built ESM bundle here catches
+// that class of breakage before it ships.
+
+import '../dist/es/index.mjs';