Tests pass despite import of nonexistent named export

[patrickshipe]

Describe the bug

Vitest seems to suppress errors when importing named exports that do not exist, but the file does (e.g. import { LolNotReal } from './utils.js'; which I do in my reproduction), with the resulting import having a value of undefined. This is problematic since when the actual code is executed with Node, Node will crash.

I'd expect Vitest to also fail in this scenario – otherwise our tests do not give confidence that this code works.

This bug also occurs with TypeScript, but I provided a JS-only minimum reproduction to remove that factor. In my reproduction both files are ESM, to remove CJS quirks out of the equation.

Reproduction

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

If you run npm run test you will see the test imports the file and passes, even logging the line showing the value of the import is undefined.

But if you run node src/basic.js you will see:

❯ node src/basic.js
file:///home/projects/vitest-dev-vitest-lomnlkfi/src/basic.js:1
import { LolNotReal } from './utils.js';
         ^^^^^^^^^^

file:///home/projects/vitest-dev-vitest-lomnlkfi/src/basic.js:1
import { LolNotReal } from './utils.js';
         ^^^^^^^^^^
SyntaxError: The requested module './utils.js' does not provide an export named 'LolNotReal'
    at ModuleJob._instantiate (https://vitestdevvitestlomnlkfi-t2wm.w-credentialless-staticblitz.com/builtins.97a3df4f.js:158:2290)

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @vitest/ui: latest => 4.0.17 
    vite: latest => 7.3.1 
    vitest: latest => 4.0.17

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.

[sheremet-va]

Yes, this is expected. The module runner is very permissive and wants to run JS code no matter what, it even interops default export! Vitest also has __dirname/__filename in every file for the same reason. See: #2841

If you are looking for a compliant environment, follow #9210

[patrickshipe]

Thank you for your response @sheremet-va ! The ability to disable module runner looks promising 🙌

I do wonder if it'd make sense/be helpful to some folks to have the ability to disable a few of the most permissive features of the module runner – e.g. this example here (being able to import something that doesn't exist). Even folks using Vite/bundlers may want to write code that behaves more closely to standards-compliant.

[sheremet-va]

Yes, we have an idea of a "strict" flag, but not a granular permissions manager.

[sheremet-va]

Closing this in favor of #10292