tsconfig paths not resolved with documented setup instructions

[benedictleejh]

Environment

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• Operating System: Linux
• Node Version: v20.19.1
• Nuxt Version: 4.1.1
• CLI Version: 3.28.0
• Nitro Version: 2.12.5
• Package Manager: pnpm@8.15.6
• Builder: -
• User Config: compatibilityDate, devtools, modules, typescript
• Runtime Modules: @nuxt/test-utils/module@3.19.2
• Build Modules: -

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Reproduction

https://stackblitz.com/edit/nuxt-starter-yt6qbe2t

Describe the bug

In the setup instructions from https://nuxt.com/docs/4.x/getting-started/testing#setup, tsconfig aliases are no longer resolved as Vitest does not resolve tsconfig paths by default. In the reproduction, simply running pnpm nuxt test will result in the error Error: Cannot find module '~/utils/add'.

The older defineVitestConfig added the necessary Nuxt alias resolutions by default, as does the new defineVitestProject, but the recommended project config for non-nuxt environment tests does not have the necessary resolutions for aliases to work. This complicates the process for users migrating from defineVitestConfig to defineVitestProject, and results in unintuitive errors for new users who prefer/use aliases over relative paths (e.g. for readability reasons).

Some possible solutions to this issue:

1. Document the need to copy relevant tsconfig paths from the generated Nuxt tsconfig to vitest.config.ts
   a. I would recommend against this solution as it is repeating information that is already stored somewhere else, and doubles the work of setting up extra tsconfig aliases if people need it in their tests
2. Recommend that people add vite-tsconfig-paths to their setup to get access to their tsconfig paths in their tests
   a. Edit: I have been playing with this for about half a day, and I can't get this to work. If anyone manages to figure out how to make vite-tsconfig-paths work with Nuxt 4's solution-style tsconfig, do let me know.
3. Provide a way for users to generate Vitest projects with the necessary resolutions in projects where the environment is not nuxt, e.g. extending defineVitestProject to handle non-nuxt environments

Additional context

No response

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