firestore-send-email kit tracking issue #3290

Tracks parity between the firestore-send-email extension (0.2.10) and the @firebase-function-kits/firestore-send-email kit.

How it was tested: both deployed side by side on a test project with matching configs, then compared on emails sent (through an SMTP sink), delivery state, events, logs, runtime settings, load, install and uninstall. Kit tested at kits @ 1c7b047, installed three ways: the README's manual setup, functions:kits:install, and ext:migrate.

Sub-issues are ordered by priority, highest first.

Issues labelled decision need a call: change the kit, or record the difference as accepted in the below "Decisions" section.

Decisions

• decision(firestore-send-email): kit/extension parity – CLI-installed kit runs Node 24, extension runs Node 22 #3325: the runtime follows the host codebase, so functions:kits:install writes Node 24 where the extension ran nodejs22. Accepted.
• decision(firestore-send-email): kit/extension parity – kit continues after an Eventarc publish failure, the extension aborts #3326: Eventarc publish failures are logged as warnings and delivery carries on, where a failed onStart publish stopped the extension sending the mail. Accepted. Documented in docs(firestore-send-email): note that a failed event publish doesn't stop delivery #3322.

Intentional Differences

• Function region: the function is placed next to the database, derived from DATABASE_REGION (multi-regions map to a Cloud Run region). The extension ran it in its own location setting, default us-central1. The Firestore trigger still fires in the database's region.
• kit- naming: functions, secrets and service accounts are named kit-<instance>-… / firebase-fn-… instead of ext-<instance>-….
• Declared roles and APIs: the kit declares datastore.user, eventarc.eventReceiver, run.invoker and eventarc.publisher, and enables firestore and eventarcpublishing, instead of relying on the Extensions platform's implicit grants.
• All four secrets required: SMTP_PASSWORD, CLIENT_ID, CLIENT_SECRET and REFRESH_TOKEN must exist at deploy, because defineSecret can't be optional.
• Eventarc channel: you create the channel and set EVENTARC_CHANNEL yourself. Publish failures are logged as warnings and no longer stop delivery (decision(firestore-send-email): kit/extension parity – kit continues after an Eventarc publish failure, the extension aborts #3326).
• Node runtime and image: the runtime follows the host codebase (functions:kits:install writes Node 24), and the base image gets automatic updates. The extension was fixed at nodejs22 with a frozen image (decision(firestore-send-email): kit/extension parity – CLI-installed kit runs Node 24, extension runs Node 22 #3325).
• Config handling: string values and secrets are trimmed (whitespace-only means unset).
• Instances and versions: all instances in a kit stanza share one package version. Extension instances were versioned separately.
• TESTING env path: can be set from .env (fix(firestore-send-email): restore the TESTING env path #3110).