Nuxt/i18n v9.1.0 breaks Vitest code coverage

[antoinezanardi]

Environment

Nuxt project info:

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• Operating System: Linux
• Node Version: v18.20.3
• Nuxt Version: 3.14.159
• CLI Version: 3.15.0
• Nitro Version: 2.10.4
• Package Manager: [email protected]
• Builder: -
• User Config: default
• Runtime Modules: @nuxtjs/[email protected]
• Build Modules: -

---

Reproduction

You can reproduce the bug with the StackBlitz here : https://stackblitz.com/edit/nuxt-starter-gpaujj?file=package.json

Run the following commands :

npm i
vitest --coverage

Describe the bug

When using Vitest to generate code coverage (with either v8 or istanbul), it appears that v9.1.0 introduces a bug that breaks the generated coverage files and their output.

Observed Behavior:

• In the provided reproduction, the generated file coverage/final-coverage.json contains only {}, which is incorrect.
• The console output shows no files being covered, even though this is inaccurate.

Expected Behavior:

• The coverage/final-coverage.json file should correctly represent the coverage data.
• The console output should accurately reflect the covered files.

Temporary Fix:

Reverting to v9.0.0 resolves the issue and restores normal functionality.

Additional context

You can also see that something's wrong one the PR that updates the package on a larger project of mine, with this job : https://github.com/antoinezanardi/werewolves-assistant-web-next/actions/runs/11915097536

(It checks that the coverage results are not empty).

Logs

[BobbieGoede]

I have no idea how this module could influence the coverage generation 🤔 Unfortunately I can't confirm this is caused by this module using the provided reproduction, even when removing Nuxt I18n, the generated coverage file seems to only contain {}. Maybe I'm doing something wrong, can you check if this is the case for you as well?

[antoinezanardi]

It looks like I can't reproduce it well either… That's a shame !

However, as odd as it is, I can assure that upgrading the version to 9.1.0 actually breaks the coverage on my project here : https://github.com/antoinezanardi/werewolves-assistant-web-next/actions/runs/11915097536

Back to the reproduction, I think that StackBlitz as some issues with coverage reporters… Maybe running it local will be different ?

[BobbieGoede]

I just tried it debugging the issue using the werewolves-assistant-web-next project.

You're right that updating to 9.1.0 seems to break the coverage generation, but installing 9.0.0 again afterwards leaves the coverage generation broken, I guess strictly speaking this means a sub dependency (higher version) is breaking the coverage generation. I'll try and see if I can narrow it down further.

[antoinezanardi]

Thanks a lot for your investigation.

You're right, downgrading it after that won't resolve the issue. I had to rollback the package-lock.json from a previous working build to make it work again.