lensPath.spec.js

import { compose } from './compose.js'
import { identity } from './identity.js'
import { inc } from './inc.js'
import { lensPath } from './lensPath.js'
import { lensProp } from './lensProp.js'
import { over } from './over.js'
import { set } from './set.js'
import { view } from './view.js'

const testObj = {
  a : [ { b : 1 }, { b : 2 } ],
  d : 3,
}

test('view', () => {
  expect(view(lensPath('d'), testObj)).toBe(3)
  expect(view(lensPath('a.0.b'), testObj)).toBe(1)
  // this is different to ramda, as ramda will return a clone of the input object
  expect(view(lensPath(''), testObj)).toBeUndefined()
})

test('set', () => {
  expect(set(
    lensProp('d'), 0, testObj
  )).toEqual({
    a : [ { b : 1 }, { b : 2 } ],
    d : 0,
  })
  expect(set(
    lensPath('a.0.b'), 0, testObj
  )).toEqual({
    a : [ { b : 0 }, { b : 2 } ],
    d : 3,
  })
  expect(set(
    lensPath('a.0.X'), 0, testObj
  )).toEqual({
    a : [
      {
        b : 1,
        X : 0,
      },
      { b : 2 },
    ],
    d : 3,
  })
  expect(set(
    lensPath([]), 0, testObj
  )).toBe(0)
})

test('over', () => {
  expect(over(
    lensPath('d'), inc, testObj
  )).toEqual({
    a : [ { b : 1 }, { b : 2 } ],
    d : 4,
  })
  expect(over(
    lensPath('a.1.b'), inc, testObj
  )).toEqual({
    a : [ { b : 1 }, { b : 3 } ],
    d : 3,
  })
  expect(over(
    lensProp('X'), identity, testObj
  )).toEqual({
    a : [ { b : 1 }, { b : 2 } ],
    d : 3,
    X : undefined,
  })
  expect(over(
    lensPath('a.0.X'), identity, testObj
  )).toEqual({
    a : [
      {
        b : 1,
        X : undefined,
      },
      { b : 2 },
    ],
    d : 3,
  })
})

test('compose', () => {
  const composedLens = compose(lensPath('a'), lensPath('1.b'))
  expect(view(composedLens, testObj)).toBe(2)
})

test('set s (get s) === s', () => {
  expect(set(
    lensPath([ 'd' ]), view(lensPath([ 'd' ]), testObj), testObj
  )).toEqual(testObj)
  expect(set(
    lensPath([ 'a', 0, 'b' ]),
    view(lensPath([ 'a', 0, 'b' ]), testObj),
    testObj
  )).toEqual(testObj)
})

test('get (set s v) === v', () => {
  expect(view(lensPath([ 'd' ]), set(
    lensPath([ 'd' ]), 0, testObj
  ))).toBe(0)
  expect(view(lensPath([ 'a', 0, 'b' ]), set(
    lensPath([ 'a', 0, 'b' ]), 0, testObj
  ))).toBe(0)
})

test('get (set(set s v1) v2) === v2', () => {
  const p = [ 'd' ]
  const q = [ 'a', 0, 'b' ]
  expect(view(lensPath(p), set(
    lensPath(p), 11, set(
      lensPath(p), 10, testObj
    )
  ))).toBe(11)
  expect(view(lensPath(q), set(
    lensPath(q), 11, set(
      lensPath(q), 10, testObj
    )
  ))).toBe(11)
})