Too simple check for localStorage causes msw to crash on Node.js 25

[wojtekmaj]

Prerequisites

• I confirm my issue is not in the opened issues
• I confirm the Frequently Asked Questions didn't contain the answer to my issue

Environment check

• I'm using the latest msw version
• I'm using Node.js version 20 or higher

Node.js version

25.0.0

Reproduction repository

n/a

Reproduction steps

Currently on Node.js 25.0.0 msw fails with the following error:

 FAIL  src/components/common/like_button.spec.tsx
  ● Test suite failed to run
                                                                                                                
    TypeError: localStorage.getItem is not a function                                                           
                                                                                                                
    > 1 | import { setupServer } from 'msw/node';                                                               
        | ^                                                                                                     
      2 |                                                                                                       
      3 | import handlers from './handlers';                                                                    
      4 |                                                                                                       
                                                                                                                
      at CookieStore.getCookieStoreIndex (node_modules/msw/src/core/utils/cookieStore.ts:44:32)                 
      at new CookieStore (node_modules/msw/src/core/utils/cookieStore.ts:25:34)                                 
      at Object.<anonymous> (node_modules/msw/lib/core/utils/cookieStore.js:90:21)                              
      at Object.<anonymous> (node_modules/msw/src/core/utils/request/storeResponseCookies.ts:1:29)              
      at Object.<anonymous> (node_modules/msw/src/core/utils/handleRequest.ts:8:38)                             
      at Object.<anonymous> (node_modules/msw/src/node/SetupServerCommonApi.ts:15:31)                           
      at Object.require (mocks/server.ts:1:1)
      at Object.require (jest.setup.ts:2:1)

(node:33156) Warning: `--localstorage-file` was provided without a valid path
(Use `node --trace-warnings ...` to show where the warning was created)                                    

This error can be tracked down to these lines:

msw/src/core/utils/cookieStore.ts

Lines 39 to 43 in d4c287c

	if (typeof localStorage === 'undefined') {
	return {}
	}
	const cookiesString = localStorage.getItem(this.#storageKey)

The problem is that in Node.js 25.0.0, localStorage is present in globalThis at all times, even if not set up properly using --localstorage-file. In such cases, an it will be an object, I believe, equal to Object.create(null).

The check in lines linked needs to be expanded to

    if (typeof localStorage === 'undefined' || typeof localStorage.getItem !== 'function') {

and poof! The error is gone.

Current behavior

Fails on Node.js 25.0.0

Expected behavior

Should not fail on Node.js 25.0.0

[tpoisseau]

% volta run --node 25 node 
Welcome to Node.js v25.1.0.
Type ".help" for more information.
> localStorage
Proxy [
  {},
  [Object: null prototype] {
    get: [Function: get],
    set: [Function: set]
  }
]
> localStorage.getItem('test')
Uncaught TypeError: localStorage.getItem is not a function
> (node:22989) Warning: `--localstorage-file` was provided without a valid path
(Use `node --trace-warnings ...` to show where the warning was created)

% volta run --node 25 node --no-webstorage
Welcome to Node.js v25.1.0.
Type ".help" for more information.
> typeof localStorage
'undefined'

% volta run --node 24 node                
Welcome to Node.js v24.11.0.
Type ".help" for more information.
> typeof localStorage
'undefined'
> 

A workaround in waiting a fix from msw or Node.js is to add --no-webstorage option

[tpoisseau]

nodejs/node#60303

[tpoisseau]

nodejs/node#60351 (comment)

Once the fix is release, the correct way to check if localStorage is available would be this method:

function localStorageIsAvailable() {
  try {
    return typeof localStorage !== 'undefined';
  } catch {
    return false;
  }
}

[kettanaito]

Hi. Thanks for reporting this. It does look like a bug in Node.js to me. I believe you've also referenced in above. I suggest waiting until this is published in Node.js. We don't normally do workarounds for anything.

I will close this because we aren't promising Node.js 25 support, to begin with. That's an experimental version and you probably shouldn't be using it directly.