TypeError: Network Request Failed

Describe the bug

I received this error whenever there’s code error on the handler code.

Environment

This unit testing running on Node environment

• msw: 0.35.0
• nodejs: 16.6.0
• npm: 7.24.1

To Reproduce

Take a look at the example of the handler code below:

import { rest } from 'msw'

export const handlers = [
  rest.post('/login', (req, res, ctx) => {
    const { username } = req.body
    i = 1 / 0
    return res(
      ctx.json({
        id: 'f79e82e8-c34a-4dc7-a49e-9fadc0979fda',
        username,
        firstName: 'John',
        lastName: 'Maverick',
      })
    )
  }),
]

Expected behavior

The error should appear like this when testing

    ReferenceError: i is not defined
        at resolver ([project path]\src\mocks\handlers.js:6:6)
        at [rest of stack traces]

Current behavior

But instead, TypeError appears

    TypeError: Network request failed

      at node_modules/whatwg-fetch/dist/fetch.umd.js:535:18
      at Timeout.task [as _onTimeout] (node_modules/jsdom/lib/jsdom/browser/Window.js:516:19)

It seems like when the handler code failed, there’s no response being sent back, resulting what it looks like timeout.

More info

I’m able to make the error shows up in the console by editing this line

https://github.com/mswjs/msw/blob/11bb2441e102666184188f9f576ac65e59b1be9d/src/handlers/RequestHandler.ts#L235

into this

      try {
        result = this.resolverGenerator || (await resolver(req, res, ctx))
      } catch (error) {
        console.error(error)
        return null
      }

but it’s kinda ugly? What’s best approach for this?

[Smankusors]

yeah it should return 500 response, but it doesn’t. The timeout returned instead.

I have tried console.log everywhere in the createRequestListener.ts, but not a single log is even appear on the console

Take a look of my modified createRequestListener

https://github.com/Smankusors/msw/blob/52ffe4117d89820c7c29152e860c4fa8ff15e2ee/src/utils/worker/createRequestListener.ts

[angeld287]

In my case adding the full Url, it didn’t show the error.

const login = rest.post('http://localhost:3001/api/auth/login', (req, res, ctx) => {