Functions Engine

TypeScript triggers on collection and auth events. Implemented in Milestone 5.

Location

src/core/functions/

  • types.ts — FunctionContext, FunctionsEngine, RegisteredTrigger
  • triggers.ts — onCreate, onUpdate, onDelete, onLogin, onRegister (exported as bakend/functions)
  • trigger-registry.ts — per-discovery trigger registration stack
  • discover.ts — scans functions/**/*.ts, resolves bakend/functions imports
  • create-functions-engine.ts — loads triggers, subscribes to Event Bus, emits lifecycle events
  • watch.ts — fs.watch debounced reload for hot reload

Trigger API

import { onCreate, onUpdate, onDelete } from "bakend/functions";

onCreate("posts", async ({ record, db, logger, event }) => {});
HelperEvent type
onCreate(collection, fn){collection}.created
onUpdate(collection, fn){collection}.updated
onDelete(collection, fn){collection}.deleted
onLogin(collection, fn)auth.login
onRegister(collection, fn)auth.register

Discovery

  • Path: {projectRoot}/functions/ (sibling to bakend.json)
  • Missing directory is skipped (no error)
  • bakend/functions imports are rewritten to the runtime triggers module before import
  • Transformed modules cached under functions/.bakend-cache/

Engine API

const functions = createFunctionsEngine({
  eventBus, db, logger,
  functionsDir: join(projectDir, "functions"),
  watch: false,
});
await functions.load();
functions.list();   // RegisteredTrigger[]
functions.reload(); // re-discover and re-subscribe
functions.shutdown();

Wired into start() via StartResult.functions.

Lifecycle Events

Emitted by the functions engine (source: functions):

  • function.started
  • function.completed
  • function.failed

Hot Reload

  • bak dev — starts with watch: true
  • bak start --watch — same behavior via flag
  • Uses fs.watch with 100ms debounce

Rules

  • Functions subscribe via Event Bus only (never called from record-store directly)
  • Handler errors never crash the process
  • Same-process execution in M5 (no worker sandbox)
  • onLogin / onRegister fire on auth.login / auth.register events (Milestone 7)
  • auth.user is populated in function context for auth events
  • storage.get(id) / storage.delete(id) available in function context (Milestone 8)

Deferred

  • HTTP functions, scheduled functions, secrets
  • Worker sandbox isolation
  • bak functions CLI management
  • Dashboard functions viewer