Add factory method(s) to avoid code duplication / custom wrappers about esmock

[koshic]

Thx, I'll continue with standalone package!

[koshic]

Another possible option - to add preprocessing magic, due to esmock loader has access to all files, including test files themself. It's much more tricky and not so clear, but theoretically can be used to injecting parent module url inside the calls, making something similar to Jest's 'mock' method, etc. Personally I don't like that way, because previously I have a lot of questions about Jest internals - 'my tests doesn't work as expected, plz help me, Master'.

[iambumblehead]

an un-tested vanilla js function-sketch

import test, { mock } from 'node:test'
import assert from 'node:assert'
import esmock from 'esmock'

const esmockFactory = ((url = import.meta.url) => (moduleId, factdefs, factgdefs) => (
  (defs, gdefs) => esmock(moduleId, url, {
    ...factdefs,
    ...Object.keys(defs).reduce((p, k) => ({
      ...k,
      ...(Object.isExtensible(factdefs[k]) && Object.isExtensible(defs[k]))
        ? ({ ...factdefs[k], ...defs[k] })
        : defs[k]
    }), factdefs || {})
  }, {
    ...factgdefs,
    ...Object.keys(defs).reduce((p, k) => ({
      ...k,
      ...(Object.isExtensible(factgdefs[k]) && Object.isExtensible(defs[k]))
        ? ({ ...factgdefs[k], ...gdefs[k] })
        : gdefs[k]
    }), factgdefs || {})
  })
))()

const esmockGetCountryJWT = esmockFactory('#src/get-country-from-jwt', {
  'my-package-A': {
    createJwt: () => ({
      countryCode: 'US'
    }),
  },
  'my-package-B': {
    isCountry: () => true
  }
})

await test("variant 1", async () => {
  const isCountry = mock.fn(() => true)
  const { getCountryFromJwt } = await esmockGetCountryJWT({
    'my-package-B': {
      isCountry: mock.fn(() => true)
    }
  })

  isCountry.mock.mockImplementationOnce(() => true)

  assert.deepEqual(getCountryFromJwt('token'), 'us')
})

await test("variant 2", async () => {
  const { getCountryFromJwt } = await esmockGetCountryJWT({
    'my-package-B': {
      isCountry: () => false
    }
  })

  assert.throws(() => getCountryFromJwt('token'), {
    message: 'Invalid country us'
  })
})

reusable factories could be returned from external package like eg "esmockfactory" below,

import test, { mock } from 'node:test'
import assert from 'node:assert'
import esmock from 'esmock'
import esmockfactory from 'esmockfactory'

const esmockfact = esmockfactory(esmock, import.meta.url)
const esmockGetCountryJWT = esmockfact('#src/get-country-from-jwt', {
  'my-package-A': {
    createJwt: () => ({
      countryCode: 'US'
    }),
  },
  'my-package-B': {
    isCountry: () => true
  }
})

await test("variant 1", async () => {
  const isCountry = mock.fn(() => true)
  const { getCountryFromJwt } = await esmockGetCountryJWT({
    'my-package-B': {
      isCountry
    }
  })

  isCountry.mock.mockImplementationOnce(() => true)

  assert.deepEqual(getCountryFromJwt('token'), 'us')
})

Imo factory-functionality should be created through an external package esmock wrapper. The reason is, factory-functionality does not require integration with esmock's loader behaviour and esmock is better (imo) if it provides only essential parts needed for mocking.

Also, the simplified area around these lines in the demo "esmockFactory" example would need to be more complicated ({ ...factdefs[k], ...defs[k] }) as this formula doesn't work in various scenarios mostly related to class instances and class properties

If an esmock-factory-creating package existed, that package could be mentioned in the README and wiki.

[koshic]

Decided to don't include such functionality into esmock package