// firebase.json
{
  "functions": {
    "predeploy": "npm run build --workspace=packages/foobar",  // NG
    // "predeploy": "npm run build --workspace packages/foobar", // OK
    // "predeploy": "npm run build --workspace\\=packages/foobar", // OK
    // "predeploy": "npm run build -w packages/foobar", // OK
    // "predeploy": "npm --prefix \"$RESOURCE_DIR\" run build", // OK
    "source": "packages/foobar"
  }
}