ESM support stopped working in Cloud Functions (GCF)

ESM support stopped working today in Google Cloud Functions (GCF) environment with Node.js 16 runtime. Trying to deploy an ESM codebase fails with the error:

To load an ES module, set "type": "module" in the package.

package.json

{
  "name": "esm",
  "type": "module",
  "exports": "./index.js",
  "packageManager": "yarn@3.2.0-rc.12"
}

index.js

export function esm(req, res) {
  res.send("PASS");
}

$ cloud functions deploy esm \
    --project=example --region=us-central1 --allow-unauthenticated --trigger-http \
    --entry-point=esm --memory=256MB --runtime=nodejs16 --source=. \
    --set-env-vars="NODE_OPTIONS=--loader=./.pnp.loader.mjs --require=./.pnp.cjs --no-warnings"

Workaround (if you want to preserve ESM in your project)

1. Bundle the code. E.g. by using Rollup and Babel wtih @babel-preset/env, target: { node: "14" } preset
2. Deploy to Node.js v14 GCF runtime. See example: GraphQL API and Relay Starter Kit → api/rollup.config.js

Ref #233, #292, https://github.com/nodejs/node/issues/41189, https://github.com/nodejs/node/pull/41198

[matthewrobertson]

This appears to be a regression in v16 of the Node.js engine. I have filed https://github.com/nodejs/node/issues/41189. Unfortunately, the work around is to use nodejs14 on GCF for now.

[matthewrobertson]

The rollout completed a few hours ago. I just confirmed that I can deploy an ESM function in europe-west1 with the nodejs16 runtime. Please re-open the bug if you are still having issues.