How to use sequence, or custom vars on Prisma?

[darr1s]

Hi there! Thanks for the great repo.

I am currently using this in my project and have noticed a few issues:

1. Prisma generated factories cannot create custom variables.
2. No sequence number accessor.
3. UUIDs are generated as strings, and createdAt fields with @default(now()) are also generated (as mentioned in the original README).

Given the current options of after + traits, I'm unsure if I should create all the factories. So, I wrote a script to generate base factories with ((id) => uuid()) based on the generated ones. I then use these base factories for my real e2e factories, making the seeders simpler and easier to manage than maintaining 100+ factories for schema models.

[ktmouk]

Hi, @darr1s. 👋

1. Prisma generated factories cannot create custom variables.

It is impossible to add new variables to the defined factory because of TypeScript limitation, but you can create a new factory with the defined factory by using .def, like below:

const baseUserFactory = defineUserFactory(db)
const { props, vars } = baseUserFactory.def

export const userFactory = await factory
  .define({
    props: {
      ...props,
      foo: () => "foo",　// add 'foo' prop
    },
    vars: {
      ...vars,
      bar: () => "bar",　// add 'bar' var
    },
  })

3. UUIDs are generated as strings, and createdAt fields with @default(now()) are also generated (as mentioned in the original README).

Yes, prisma-factory currently does not support generating default values based on native database type attributes because DMMF, used in prisma-factory, does not support passing native types (ref: prisma/prisma#10252). Therefore, one simple way is to override the id property yourself, as you already described.

2. No sequence number accessor.

Could you please tell me more about the sequence number accessor? Is it similar to sequences in factory_bot?

[darr1s]

Hi @ktmouk ,

Thanks for the prompt reply!

For sequence, yes it is a sequence number like factory_bot, useful when we are using .buildList() or .createList()

[ktmouk]

You can implement sequence generator by writing simple closure.

const seq = <O>(iteratee: (count: number) => Promise<O> | O) => {
  let count = 0;
  return () => iteratee(count++);
};

export const userFactory = await factory
  .define({
    props: {
      name: seq(0, (n) => `name-${n}`)
    },
    vars: {}
  })

Actually, factory-js had the seq feature, which is the same as factory_bot, but we removed it at #17. This feature was intended to generate unique values and avoid UNIQUE constraint errors. However, since Jest/Vitest runs tests in multiple threads by default, it could not generate unique values across threads. But if you just want to generate sequence numbers, I think the above function would be helpful for you.

---

FYI: If the table colums has the @default attribute, you can set undefined to props to use the default value that Prisma generates.

// schema.schema
model User {
  id String @id @default(dbgenerated("gen_random_uuid()")) @db.Uuid
  createdAt DateTime @default(now()) @db.Timestamptz(3)
}

// factory.ts
export const userFactory = defineUserFactory(db).props({
  id: () => undefined,  
  createdAt: () => undefined
})