Faker Dataset

Generate a deterministic set of user records with correlated person and location fields, using all of the Faker provider's generator kinds.

Source

examples/faker-dataset/rank.toml

manifestVersion = 1

[package]
name = "faker-dataset"
version = "0.1.0"
source = "."

[providers]
faker = { registry = "npm", package = "@rank-lang/plugin-faker", version = "0.1.0" }

examples/faker-dataset/main.rank

/// Generates a deterministic seed dataset of users using the Faker provider.
/// Shows correlated Person and Location projections, all generator kinds
/// (UUID, Int, Boolean, DateTime, Person, Location), and multi-record
/// collection generation with Emit::manifest.

use faker::{ Boolean, DateTime, Generate, Int, Location, Person, UUID }
use faker::types::{ Spec }
use std::Time
use std::list::{ range }
use std::collections::{ map }
use std::Emit
use std::Path

/// --- Types ---

Address = Object {
  street: string,
  city: string,
  country: string,
}

User = Object {
  id: string,
  firstName: string,
  lastName: string,
  email: string,
  age: number,
  address: Address,
  role: string,
  active: bool,
  createdAt: Time::Instant,
  score: number,
}

/// --- Generator descriptors ---

seed = 1

refDate: Time::Instant = Time::parse(`2025-01-01T00:00:00Z`, { format: `RFC3339` })

person = Person { sex: `female` }
location = Location {}

userSpec: Spec<User> = {
  id: UUID {},
  firstName: person.firstName,
  lastName: person.lastName,
  email: person.email,
  age: Int { min: 18, max: 65 },
  address: {
    street: location.street,
    city: location.city,
    country: location.country,
  },
  role: `member`,
  active: Boolean { probability: 0.8 },
  createdAt: DateTime {
    past: { years: 3 },
  },
  score: Int { min: 0, max: 1000 },
}

/// --- Generate 20 users ---

count = 20

users: [User] = range(count)
  |> map(|_, ctx| Generate<User> {
       spec: userSpec,
       seed,
       itemKey: ctx.index,
       locale: `en_US`,
       refDate,
     })

/// --- Emit ---

pub main = || Emit::manifest({
  entries: [
    {
      path: Path::join([`users.json`]),
      format: `json`,
      value: users,
    },
  ]
})

Output

// users.json (first two records shown)
[
  {
    "id": "a3f1c2d4-...",
    "firstName": "Sophia",
    "lastName": "Martinez",
    "email": "Sophia.Martinez@example.com",
    "age": 34,
    "address": {
      "street": "742 Evergreen Terrace",
      "city": "Springfield",
      "country": "United States"
    },
    "role": "member",
    "active": true,
    "createdAt": { "epochMillis": 1672531200000, "offsetMinutes": 0 },
    "score": 812
  },
  {
    "id": "b7e8d9f0-...",
    "firstName": "Olivia",
    "lastName": "Chen",
    "email": "Olivia.Chen@example.com",
    "age": 27,
    "address": {
      "street": "18 Oak Lane",
      "city": "Portland",
      "country": "United States"
    },
    "role": "member",
    "active": false,
    "createdAt": { "epochMillis": 1698796800000, "offsetMinutes": 0 },
    "score": 441
  }
]

Key concepts

• Person projections — person.firstName, person.lastName, person.email, person.age, person.address are correlated: they all come from the same generated person, so the email matches the name on every record.
• Location projections — location.street, location.city, location.country are similarly correlated from a single generated location.
• Spec<T> — the spec mirrors the shape of User. Literal values (role: \member``) are passed through unchanged; generator descriptors are evaluated per record.
• seed + itemKey — seed fixes the base RNG; itemKey: ctx.index derives a distinct sub-stream per record, so record 0 and record 1 are always different but always the same across runs.
• refDate — anchors relative date generators like DateTime { past: { years: 3 } } to a fixed point in time, keeping the dataset stable even as the current date changes.
• Boolean { probability: 0.8 } — approximately 80% of users will have active: true.

Run it

rank examples/faker-dataset --file-root out/

Writes out/users.json. Requires the @rank-lang/plugin-faker package — see the Faker Provider docs for installation.