Cannot mock 204 response

Describe the bug

It seems to be impossible to construct a 204 (No content) response. When I just invoke return res(ctx.status(204)) I get the following error: Failed to construct ‘Response’: Response with null body status cannot have body It does not help trying to add ctx.json({}) or ctx.body(null) - the body seems to end up as the empty string regardless. This fails when msw is trying to invoke const response = new Response(payload.body, payload) in the function createResponseListener as responses with status 204 are not allowed to have any body.

Environment

• msw: 0.25.0
• Chrome: 87.0.4280.141

[SerkanSipahi]

@kettanaito

You are right. It was my mistake. The 204 response contained an empty ( {} ) body payload in my case. As you suggested res(ctx.status(204)) is the right way here.

Thank you for your support and time.

[kettanaito]

Hi, @SerkanSipahi. The change you’re referencing has been successfully merged:

https://github.com/mswjs/msw/blob/9a43bc9cba49f3c18b1ab1ed700d3f41f9fe86f5/src/mockServiceWorker.js#L129-L130

Could you please ensure you’re running msw@0.29.0?

# To verify
$ npm ls msw

## To install latest
$ npm install msw@latest

In my case status-code 204 with a json response produces exactly the same error

Perhaps the response you’re composing is not a valid HTTP response? A response with a 204 status code cannot have a response body, that’d be a violation of the spec. Can you please try composing a mocked 204 response without any response body?

return res(ctx.status(204))