Feature: Enhanced Lazy Evaluation

[Goldziher]

Feature: Enhanced Lazy Evaluation

Extend lazy evaluation capabilities beyond the current use method to support more complex scenarios.

Current State

The library already has a use() method that enables lazy evaluation for circular references and complex relationships. This feature would enhance and extend these capabilities.

Proposed Features

• Enhanced lazy method with field dependencies

  • Allow specifying which fields trigger re-evaluation
  • Support for conditional dependencies

• Async lazy evaluation support

  • Handle promises in lazy evaluation
  • Maintain type safety with async operations

• Conditional lazy evaluation

  • Evaluate only when certain conditions are met
  • Support for predicate functions

• Proper type inference

  • Preserve TypeScript type inference throughout
  • No degradation of type safety

Implementation Requirements

• Build upon existing use() method infrastructure
• Maintain backward compatibility
• Ensure TypeScript type inference is preserved
• Consider integration with circular reference handling
• Add comprehensive tests for all new lazy evaluation patterns

Example API

// Field dependencies
const factory = new Factory<User>((faker) => ({
  id: faker.string.uuid(),
  name: faker.person.fullName(),
  email: factory.lazy((user) => `${user.name.toLowerCase().replace(' ', '.')}@example.com`, ['name'])
}));

// Async lazy evaluation
const factory = new Factory<User>((faker) => ({
  id: faker.string.uuid(),
  apiKey: factory.lazyAsync(async (user) => await generateApiKey(user.id))
}));

// Conditional lazy evaluation
const factory = new Factory<Order>((faker) => ({
  status: faker.helpers.arrayElement(['pending', 'completed', 'cancelled']),
  completedAt: factory.lazyIf(
    (order) => order.status === 'completed',
    () => faker.date.recent()
  )
}));

Testing Requirements

• Unit tests for each lazy evaluation pattern
• Type-level tests to ensure inference works correctly
• Performance tests for complex lazy evaluation chains
• Integration tests with existing use() method