Vitest 4 can no longer have projects with `import ... 'bun'`

[matthew-gladman-oua]

Describe the bug

When importing anything from bun, Vitest v4 throws an error:

src:

import { $ } from 'bun';

export async function example() {
  await $`echo hi`;
}

error:

Error: Failed to resolve entry for package "bun". The package may have incorrect main/module/exports specified in its package.json.
  Plugin: vite:import-analysis

In Vitest v3, this code worked fine (I suspect because the calls to bun were mocked away), but in v4 it no longer works. Looking at the bun package.json it's a valid error... (there is no entry script). But I'm not sure if this check is useful here as we're never actually importing the file...

Mocking out the file that uses this import does not help, nor does mocking bun itself 😭

Reproduction

https://stackblitz.com/edit/vitejs-vite-j93mxww4?file=src%2Fenv.test.ts

System Info

System:
    OS: macOS 26.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 500.44 MB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.11.1 - /Users/matthew.gladman/.volta/tools/image/node/24.11.1/bin/node
    npm: 11.6.4 - /Users/matthew.gladman/.volta/tools/image/npm/11.6.4/bin/npm
    bun: 1.3.4 - /Users/matthew.gladman/projects/catalogue-verse/node_modules/.bin/bun
  Browsers:
    Chrome: 143.0.7499.41
    Edge: 143.0.3650.80
    Firefox: 145.0.1
    Safari: 26.1

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• 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.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[hi-ogawa]

This doesn't look like an expected behavior but nonetheless bun package case seems like rather an edge case.

The workaround I found is aliasing to mocked file manually like this https://stackblitz.com/edit/vitejs-vite-drbpu9gb?file=vitest.config.mts

import { defineConfig } from 'vitest/config';
import path from 'node:path';

export default defineConfig({
  ...
  resolve: {
    alias: {
      bun: path.join(import.meta.dirname, './bun-mock.js'),
    },
  },
});

[matthew-gladman-oua]

Yeah certainly is an edge case, not the end of the world if it doesn't get fixed... I'll give the workaround a crack, cheers

EDIT: Can confirm this workaround works great 👌