regexp matchers cannot always be overwritten

[ryuuji3]

Version: latest

Description: when you enable overwriteRoutes, and mock a route twice with a RegExp, it will not mock with the response of the second mock unless you share the same RegExp instance.

Reproduction:

import fetchMock from 'fetch-mock'

fetchMock.config.overwriteRoutes = true

it('foo', () => {
  fetchMock.mock(/example\.com/, 200)

  const successResponse = await fetch('example.com')
  expect(successResponse.status).toBe(200)

  fetchMock.mock(/example\.com/, 404)

  const failureResponse = await fetch('example.com')
  expect(failureResponse.status).toBe(404) // nope, its 200
})

If, however you amend the above to

import fetchMock from 'fetch-mock'

fetchMock.config.overwriteRoutes = true

const exampleMatcher = /example\.com/

it('foo', () => {
  fetchMock.mock(exampleMatcher, 200)

  const successResponse = await fetch('example.com')
  expect(successResponse.status).toBe(200)

  fetchMock.mock(exampleMatcher, 404)

  const failureResponse = await fetch('example.com')
  expect(failureResponse.status).toBe(404) // yep works!
})

it works as expected.

I narrowed this problem down to some code that did a triple equality check but I don't remember where I saw it. That would explain though why a shared reference works, but the earlier one doesn't.

[wheresrhys]

I think this is expected behaviour, though I agree it's not obvious and not documented very well.

To get more transparent behaviour it's best to name your routes

it('foo', () => {
  fetchMock.mock(/example\.com/, 200, {name: 'myroute'})

  const successResponse = await fetch('example.com')
  expect(successResponse.status).toBe(200)

  fetchMock.mock(/example\.com/, 404, , {name: 'myroute'})

  const failureResponse = await fetch('example.com')
  expect(failureResponse.status).toBe(404) // should be 404
})

[ryuuji3]

Thank you, naming mocked routes was exactly what we needed to do!