Subpath import conditions are not processed

[nazarhussain]

Describe the bug

If we have a package subpath imports defined with custom conditions, vitest always runs resolve to import and default condition.

Say we have sub path import with conditions. If we run the scripts in general with bun, nodejs etc the import conditions are respected.

  "imports": {
    "#my-lib": {
      "bun": "./lib/bun_lib.js",
      "import": "./lib/node_lib.js" 
    }
  },

But when we run tests on a file which is using that import it does always use import condition.

And that is not related to the Bun or any other runtime. Any condition under subpath imports are not processed by when imported inside the tests for the Vitest.

Tried to add resolve config, but that also does not work.

resolve:  {
   conditions: ['bun', 'import', 'default']
}

Reproduction

Full code is given at:

https://github.com/nazarhussain/vitest-subpath-import-conditions

And we run with NodeJS

npx vitest run 

 RUN  v4.0.8 /Users/nazar/Hub/Lodestar/dev/vitest-import-alias

stdout | test/index.test.js > test > add
sum from node

 ✓ test/index.test.js (1 test) 1ms
   ✓ test (1)
     ✓ add 1ms

 Test Files  1 passed (1)
      Tests  1 passed (1)

And if we run with Bun.

bun x --bun vitest run 

 RUN  v4.0.8 /Users/nazar/Hub/Lodestar/dev/vitest-import-alias

stdout | test/index.test.js > test > add
sum from node

 ✓ test/index.test.js (1 test) 3ms
   ✓ test (1)
     ✓ add 2ms

 Test Files  1 passed (1)
      Tests  1 passed (1)
   Start at  09:42:28

System Info

System:
    OS: macOS 26.1
    CPU: (11) arm64 Apple M3 Pro
    Memory: 142.50 MB / 18.00 GB
    Shell: 5.9 - /opt/homebrew/bin/zsh
  Binaries:
    Node: 22.13.0 - /Users/nazar/.asdf/installs/nodejs/22.13.0/bin/node
    Yarn: 1.22.22 - /Users/nazar/.asdf/installs/nodejs/22.13.0/bin/yarn
    npm: 10.9.2 - /Users/nazar/.asdf/plugins/nodejs/shims/npm
    pnpm: 10.13.1 - /Users/nazar/.bun/bin/pnpm
    bun: 1.3.1 - /Users/nazar/.asdf/shims/bun
    Deno: 2.2.8 - /Users/nazar/.asdf/shims/deno
  Browsers:
    Brave Browser: 142.1.84.135
    Edge: 140.0.3485.54
    Safari: 26.1
  npmPackages:
    vitest: ^4.0.8 => 4.0.8

Used Package Manager

npm

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[hi-ogawa]

This is a same as #8764. For non-browser/non-jsdom testing, conditions can be set inside ssr.resolve.conditions https://vite.dev/config/ssr-options#ssr-resolve-conditions

import {defineConfig} from "vitest/config";

export default defineConfig({
  ssr: {
    resolve: {
      conditions: ["bun"]
    },
  },
});

$ npx vitest

 DEV  v4.0.8 /home/hiroshi/code/tmp/vitest-subpath-import-conditions

stdout | test/index.test.js > test > add
sum from bun

[nazarhussain]

@hi-ogawa I tried resolve.conditions didn't knew about ssr.resolve.conditions. Thanks for sharing it.

[nazarhussain]

For other's reference who come across this issue. To actually make it work across the both Bun and Node, we have to add up programatic conditions.

const isBun = "bun" in process.versions;

export default defineConfig({
  ssr: {
    resolve: {
      conditions: isBun ? ["import", "bun"] : ["import"],
    },
  },
});