Loopback-next: Add support for seeders

[amrsalama]

Suggestion

This feature is inspired by Laravel seeding system.
We can have CLI command to generate seeders for repositories, for example in src/seeders directory.

Examples

Example for seeder file

import {UserRepository} from '../repositories';

interface Seeder {
  run(): Promise<void>;
}

export class UserSeeder implements Seeder {
  constructor(private userRepo: UserRepository) {}

  async run() {
    await this.userRepo.create({
      username: 'admin',
      password: 'password',
      email: '[email protected]',
      name: 'John Doe',
    });
  }
}

In application.ts, following what was stated in migrations docs

async migrateSchema(options?: SchemaMigrationOptions) {
  await super.migrateSchema(options);
  new UserSeeder(await this.getRepository(UserRepository)).run();
}

Of course we can enhance this feature by adding more flags to npm run migrate to allow seeding --seed.

And to achieve the maximum benefit of the seeding system, We can define factory feature in the Entity model to allow auto generated instances from models.

Acceptance criteria

TBD - will be filled by the team.

[dougal83]

There is also the option of seeding via docker that is worth considering.

[dhmlau]

@amrsalama, I've also created a blog post on how to seed a database using the life cycle observers in LoopBack 4. https://medium.com/loopback/loopback-quick-tip-seeding-database-using-life-cycle-observer-8ddca55fea5c.

[dougal83]

@amrsalama, I've also created a blog post on how to seed a database using the life cycle observers in LoopBack 4. https://medium.com/loopback/loopback-quick-tip-seeding-database-using-life-cycle-observer-8ddca55fea5c.

@dhmlau Good article. You could expand this example by using faker for other data types.

[dhmlau]

Thanks @dougal83! Good to know about this package. :)

[dhmlau]

I think this seeder capability would make a good LoopBack extension (instead of putting as part of the core). @strongloop/loopback-maintainers , what's your thoughts on that?

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