Hooks

Lifecycle hooks fire at two levels: directly on the seeder class, and globally on runSeeders.

Class-level hooks

Define hooks as methods on a seeder class to run logic around that specific seeder's run() call:

@Seeder({ dependencies: [UserSeeder] })
class PostSeeder implements SeederInterface {
  async onBefore() {
    console.log('PostSeeder starting...')
  }

  async run(ctx: SeederRunContext) {
    await seed(Post).saveMany(50, ctx)
  }

  async onSuccess(durationMs: number) {
    console.log(`PostSeeder done in ${durationMs}ms`)
  }

  async onError(error: unknown) {
    console.error('PostSeeder failed', error)
  }

  async onFinally(durationMs: number) {
    // Always runs — mirrors try/catch/finally
  }
}

Method	When it fires
onBefore()	Before run() executes
onSuccess(durationMs)	After run() completes successfully
onError(error)	When run() throws — the error is re-thrown after this returns
onFinally(durationMs)	Always — whether run() succeeded or threw

Global hooks on runSeeders

Pass callbacks to runSeeders for cross-cutting concerns that span all seeders, such as notifications or metrics:

await runSeeders([UserSeeder, PostSeeder], {
  em,
  onBefore: () => console.log('Seeding started'),
  onSuccess: (seeders, durationMs) =>
    console.log(`All done in ${durationMs}ms — ran: ${seeders.map((s) => s.name).join(', ')}`),
  onError: (seeder, error) =>
    console.error(`${seeder.name} failed`, error),
  onFinally: (durationMs) => console.log(`Seeding finished in ${durationMs}ms`),
})

Callback	When it fires
onBefore()	Once, before any seeder runs
onSuccess(seeders, durationMs)	Once, after all seeders succeed — receives the list of seeders that ran (excluding skipped ones) and the total duration
onError(seeder, error)	Once, when a seeder throws — receives the failing seeder and the error. The error is re-thrown after this returns
onFinally(durationMs)	Once, always — whether all succeeded or one threw

Class-level hooks fire first, then runSeeders-level hooks.

Skipping seeders

Pass a skip callback to conditionally bypass individual seeders. Return true to skip, false (or nothing) to run:

const alreadyRun = new Set(['UserSeeder'])

await runSeeders([UserSeeder, PostSeeder], {
  em,
  skip: (seeder) => alreadyRun.has(seeder.name),
})
// UserSeeder is skipped, PostSeeder runs normally

Skipped seeders do not trigger class-level hooks. The global onSuccess receives only the seeders that actually ran.