@electric-sql/d2mini/tests/operators/keying-types.test.ts

D2Mini is a minimal implementation of Differential Dataflow for performing in-memory incremental view maintenance.

import { describe, it, expectTypeOf } from 'vitest'
import { D2 } from '../../src/d2.js'
import { keyBy, unkey, rekey, Keyed } from '../../src/operators/keying.js'
import { IStreamBuilder } from '../../src/types.js'

interface TestItem {
  id: number
  name: string
  value: number
}

describe('keying operator types', () => {
  it('should correctly type keyBy', () => {
    const d2 = new D2()
    const input = d2.newInput<TestItem>()

    const keyed = input.pipe(keyBy((item) => item.id))
    expectTypeOf(keyed).toEqualTypeOf<IStreamBuilder<Keyed<number, TestItem>>>()
  })

  it('should correctly type unkey', () => {
    const d2 = new D2()
    const input = d2.newInput<Keyed<number, TestItem>>()

    const unkeyed = input.pipe(unkey())
    expectTypeOf(unkeyed).toEqualTypeOf<IStreamBuilder<TestItem>>()
  })

  it('should correctly type rekey', () => {
    const d2 = new D2()
    const input = d2.newInput<Keyed<number, TestItem>>()

    const rekeyed = input.pipe(rekey((item) => item.name))
    expectTypeOf(rekeyed).toEqualTypeOf<
      IStreamBuilder<Keyed<string, TestItem>>
    >()
  })

  it('should maintain type safety through chaining', () => {
    const d2 = new D2()
    const input = d2.newInput<TestItem>()

    const result = input
      .pipe(keyBy((item) => item.id))
      .pipe(rekey((item) => item.name))
      .pipe(unkey())

    expectTypeOf(result).toEqualTypeOf<IStreamBuilder<TestItem>>()
  })
})