Addon-vitest: Fix coverage when restarting Vitest due to config change

[JReinhold]

Closes #30900

What I did

The issue was technically already fixed in #30875, where coverage mode became more resilient and always restarted Vitest when a run was triggered with coverage mode that didn't match the currently running mode:

storybook/code/addons/vitest/src/node/vitest-manager.ts

Lines 201 to 213 in 71a080b

	const { watching, config } = this.testManager.store.getState();
	const coverageShouldBeEnabled =
	config.coverage && !watching && (runPayload?.storyIds?.length ?? 0) === 0;
	const currentCoverage = this.vitest?.config.coverage?.enabled;
	if (!this.vitest) {
	await this.startVitest({ coverage: coverageShouldBeEnabled });
	} else if (currentCoverage !== coverageShouldBeEnabled) {
	await this.restartVitest({ coverage: coverageShouldBeEnabled });
	} else {
	await this.vitestRestartPromise;
	}

However restarting Vitest due to config change didn't correctly set coverage mode, so it could result in:

1. Enable coverage
2. Run all tests
3. (This restarts Vitest with coverage enabled)
4. Change Vitest config
5. (This restarts Vitest with coverage disabled)
6. Run all tests
7. (This restarts Vitest again to enable coverage)

This PR eliminates step 7, because step 5 will have the correct coverage mode.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
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  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

Greptile Summary

Updated the VitestManager in /code/addons/vitest/src/node/vitest-manager.ts to correctly apply the coverage mode when restarting Vitest after configuration changes.

• Modified startVitest to require an explicit coverage boolean.
• Removed redundant waiting on the prior restart promise in restartVitest.
• Updated the config change listener to fetch the current coverage state from the test manager store.
• Ensured the correct coverage mode is maintained post-config change, preventing unnecessary restarts.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 71a080b.

Command	Status	Duration	Result
nx affected -t check -c production --parallel=7	✅ Succeeded	6s	View ↗
nx run-many -t build -c production --parallel=3	✅ Succeeded	4m 10s	View ↗

---

☁️ Nx Cloud last updated this comment at 2025-04-04 12:43:45 UTC

[JReinhold]

this was already called within this.restartVitest

[greptile-apps]

LGTM

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