Fix docs Meta resolution for split CSF4 story chunks

[raashish1601]

Fixes #34373.

Summary

• fall back to named story exports when <Meta of={Stories} /> receives a split namespace object without a default export
• keep <Meta of={...} /> strict by refusing mixed namespaces whose story exports resolve to different CSF files
• add docs-context regressions for the split-chunk CSF4 path and the mixed-namespace guard

Testing

• corepack yarn --cwd code build storybook --no-watch --no-prod
• corepack yarn --cwd code vitest run --config core/vitest.config.ts core/src/preview-api/modules/preview-web/docs-context/DocsContext.test.ts core/src/preview-api/modules/preview-web/render/MdxDocsRender.test.ts

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of module namespace objects without default exports in story file resolution.
  • Enhanced module export inference to better resolve stories from namespace objects by scanning exported values.

• Tests

  • Expanded coverage for scenarios where story modules lack default exports.
  • Added validation for edge cases involving multi-source story exports.
  • Updated test utilities to support optional default export configuration.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 400fcc56-6aff-449b-ae3e-d60a06c47376

📥 Commits

Reviewing files that changed from the base of the PR and between 0efef13 and 183acc5.

📒 Files selected for processing (3)

• code/core/src/preview-api/modules/preview-web/docs-context/DocsContext.test.ts
• code/core/src/preview-api/modules/preview-web/docs-context/DocsContext.ts
• code/core/src/preview-api/modules/preview-web/docs-context/test-utils.ts

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📝 Walkthrough

Walkthrough

Enhanced DocsContext module resolution to support namespace objects lacking default exports. Added conditional mapping for default exports, implemented fallback logic to infer CSF files by scanning object values and matching stories, and expanded test coverage accordingly.

Changes

Cohort / File(s)	Summary
Implementation code/core/src/preview-api/modules/preview-web/docs-context/DocsContext.ts	Conditional CSF file mapping for default export presence; added fallback resolution logic scanning object values to infer CSF files when direct lookup fails; minor formatting adjustments.
Test Coverage code/core/src/preview-api/modules/preview-web/docs-context/DocsContext.test.ts	New test cases for referenceMeta with namespace objects lacking default export; extended resolveOf tests for exports sharing only story references; reformatted existing expectations for readability.
Test Utilities code/core/src/preview-api/modules/preview-web/docs-context/test-utils.ts	Extended csfFileParts function signature with optional includeDefaultExport parameter (defaults to true) to conditionally shape moduleExports structure.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• storybookjs/storybook#33280: Modifies DocsContext's module namespace resolution logic with fallback scanning of object values to map exports to CSF files, directly related to this PR's enhanced export resolution approach.

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[valentinpalkovic]

Hi @raashish1601 ,

Due to a recent high volume of unreviewed AI-generated PRs, we are requesting verification and proof that the implemented fix actually works. Please provide a simple GIF/Video or image of how the bugfix works, optimally with before-and-after comparisons.

Thank you for your understanding!

[valentinpalkovic]

Hi @raashish1601,

We requested verification that this PR works as intended, but haven't received a response in over two weeks. We're closing this PR for now.

If you'd like to continue working on this, feel free to reopen the PR with the requested verification (a GIF/video or screenshot showing before-and-after behavior).

Thank you for your contribution!