Export overrides broken in tests with Vite 6.3.0+

[jbaldassari]

Describe the bug

After upgrading Vite to 6.3.0+, almost all of my tests running in Vitest started failing. I eventually figured out that all of the failing tests relied on a React Testing Library custom render function. RTL recommends implementing custom render functions in the following way, by overriding the render export with a local implementation:

// re-export everything
export * from '@testing-library/react'

// override render method
export {customRender as render}

In all versions of Vite prior to 6.3.0 this worked fine, but in 6.3.0 and newer it no longer works. Instead, the original render function from @testing-library/react is exported rather than the custom render function. It seems like Vite is remembering the first render it sees and ignoring the subsequent export which had previously acted as an override.

I didn't see anything in the changelog about this override behavior changing. The only recent change I see in 6.3.0 related to export handling is this: #18983

I haven't been able to come up with a reproduction case that works with Vite alone. It seems to occur only when the exports are being imported by a test running with Vitest. So I'm not sure if this is actually a Vite issue, a Vitest issue, or only an issue when the two are used together. I thought I'd start with a Vite issue, but I can move this over to Vitest if it would be more appropriate.

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-mrcqdpn5?file=src%2Fbasic.ts

Steps to reproduce

I created 2 stackblitz examples. The only difference between the two is that one uses Vite 6.2.6 and the other uses Vite 6.3.0. The tests pass in 6.2.6 but fail in 6.3.0 because 6.3.0 does not override the export properly.

• Working 6.2.6 example
• Broken 6.3.0 example

The basic.ts imports a broken implementation of the squared function and then overrides it with a working implementation:

export const correctSquared = (n: number) => n * n;

export * from './wrong.ts';
export { correctSquared as squared };

With Vite 6.2.0 the working implementation overrides the broken one, and the tests pass. With Vite 6.3.0 the override is ignored, and the tests fail.

System Info

System:
    OS: Linux 6.12 Gentoo Linux
    CPU: (16) x64 AMD Ryzen 7 PRO 8840HS w/ Radeon 780M Graphics
    Memory: 14.03 GB / 89.99 GB
    Container: Yes
    Shell: 5.2.37 - /bin/bash
  Binaries:
    Node: 23.6.0 - ~/.nvm/versions/node/v23.6.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v23.6.0/bin/yarn
    npm: 10.9.2 - ~/.nvm/versions/node/v23.6.0/bin/npm
    pnpm: 9.15.9 - ~/.nvm/versions/node/v23.6.0/bin/pnpm
  Browsers:
    Brave Browser: 135.1.77.100

Used Package Manager

pnpm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[jbaldassari]

I should mention the workaround is to exclude render from the initial export and just export the things other than render that you need:

export {act, fireEvent, screen, waitFor, waitForElementToBeRemoved} from '@testing-library/react';
export {customRender as render};

It's not ideal because whenever you need something new from testing library you have to go and export it there, but it does resolve the immediate problem if you need Vite 6.3.0+

[hi-ogawa]

Duplicate of #19898. It should be fixed on Vitest vitest-dev/vitest#7846 and your repro is passing with the latest Vitest 3.1.2 https://stackblitz.com/edit/vitest-dev-vitest-5yeick5f?file=src%2Fbasic.ts

[jbaldassari]

Thanks. Confirmed that vitest 3.1.2 works.