Docgen: Only add react-docgen info when a component is defined in the file

[glenjamin]

This avoids errors when a component is being imported and re-exported under a different name via a barrel file or similar.

Closes #26074

What I did

The issue occurs when the react-docgen plugin is attempting to add the additional metadata into a file that exports the component, but doesn't contain the definition or a local with the same name.

I couldn't see enough information in the react-docgen handlers to distinguish between a re-export and a definition, so I've made the extra docgen handler already defined in this loader make a note of the filename from the component definition.

When modifying the AST to add the docgen info, we only assign the info if the definition file is the same as the file we're transforming. This could potentially lead to other scenarios no longer adding the docgen info, but I believe that as long as the file containing the definition is still being processed by the loader, it should only be removing redundant re-assignments.

I'm not especially precious about taking this approach to resolve the issue, so please let me know if an alternative approach is preferred and I can give that a go instead.

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

While I was able to to add a story to the sandbox which reproduced the issue, I struggled to see how this is executed as part of the testing/CI process, so I'd appreciate any pointers if there's something I've missed.

Manual testing

1. Run a sandbox for react-webpack-18-ts
2. Open Storybook in your browser
3. Access any renderers/react/js-argtypes story
4. Without the fix, we see the following error:

   PropsWriter is not defined
   
   ./src/stories/renderers/react/docgen-components/js-re-exported-component/input.jsx@http://localhost:6006/stories-renderers-react-js-argtypes-stories.iframe.bundle.js:4238:1
   

5. With this change, there is no longer an error

Documentation

I don't believe any documentation is required.

• 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/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.

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[hanshank]

@glenjamin @valentinpalkovic

• Any idea if this will be merged anytime soon?

[valentinpalkovic]

Currently, we have a feature freeze. As soon as Storybook 8.1 is published next week, we will unfreeze next and we will be able to merge this PR.

[valentinpalkovic]

LGTM!

@glenjamin Thank you so much for your contribution. Amazing work. I've added another commit to actually also apply your changes to the react-vite framework.

[glenjamin]

Thanks! will this be backported to v7, or is it v8 only?

[soren121]

Separately, I would also like to see this included in the next patch release (8.1.x) if possible! This bug has been a blocker for my team upgrading to Storybook 8.

And many thanks for the fix @glenjamin! This bug has been on my list to look into, but you got to it first :)

[valentinpalkovic]

It will not be backported to 7. it will be part of the next patch release 8.1.1 :)