Core: Ignore empty files when indexing

[JReinhold]

Closes #

What I did

Ignored empty and almost-empty files (whitespace only) during indexing. Previously, the terminal would show an error as soon as you created a Card.stories.tsx file, and then you'd have to fill it in afterwards. Now that error goes away.

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

Create an empty stories file while Storybook is running. Observe no errors, and that adding stories to the file still works.

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.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • 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 publish.yml --field pr=<PR_NUMBER>

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of empty or whitespace-only story files to prevent unnecessary processing.

• Tests

  • Updated test infrastructure and added validation for empty story file scenarios.

• Chores

  • Updated linting configuration to ignore additional story files.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit fc65414

Command	Status	Duration	Result
nx run-many -t compile,check,knip,test,pretty-d...	❌ Failed	10m	View ↗

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☁️ Nx Cloud last updated this comment at 2026-02-05 14:16:41 UTC

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes migrate CSF parsing from readCsf to loadCsf API across the codebase, including implementation and test files. Added empty file handling to return early for whitespace-only story files. Updated corresponding test mocks and assertions, plus new test coverage for empty file scenarios.

Changes

Cohort / File(s)	Summary
ESLint Configuration .eslintignore	Added ignore rule for empty mock data story file to exclude from linting.
CSF Parsing Migration core/src/core-server/presets/common-preset.ts, core/src/core-server/utils/StoryIndexGenerator.test.ts	Replaced readCsf with loadCsf API. Added guard for empty/whitespace-only files to return early with empty index. Updated test mocks, imports, and assertions to use new loadCsf API. Added new test case for empty file handling.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• CSF: Add Storybook test syntax (Storybook v10) #32455 — Addresses CSF parsing API migration from readCsf to loadCsf with related StoryIndexGenerator and common-preset updates.
• Core: Add missing subtype props #32490 — Modifies StoryIndexGenerator.test.ts and csf-tools mock usage, switching from readCsf to loadCsf with test assertion updates.

✨ Finishing touches

• 📝 Generate docstrings

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[Sidnioulz]

QA Ok