Controls: Load controls for stories from a composed ref

[TheSeydiCharyyev]

What I did

Fixes #34553 — controls never load for a story served from a composed Storybook ref (refs / extends: true). ControlsPanel only watched the host's global previewInitialized flag, which stays false for ref stories — their readiness is tracked per-ref in state.refs[refId].previewInitialized. So isLoading never cleared and the args table showed loading skeletons forever.

The fix reads the ref's previewInitialized when the current story belongs to a ref, and falls back to the global flag otherwise.

Manual testing

• Repro: compose a second Storybook via refs and open one of its stories — its Controls now load instead of showing skeletons.
• Added a regression story ControlsPanel.stories.tsx (RefStoryControlsLoad): it mocks ManagerContext for a ref story while the host's global previewInitialized is still false, and asserts the controls render. Verified it fails on the pre-fix behaviour and passes with the fix:

yarn vitest run --config code/vitest.config.storybook.ts core/src/controls/components/ControlsPanel.stories.tsx

Closes #34553

Summary by CodeRabbit

• Bug Fixes

  • Fixed ControlsPanel to correctly determine preview initialization status for stories in composed refs, ensuring controls load properly when referencing stories from other Storybook instances (resolves issue #34553).

• Tests

  • Added regression test for composed ref story control rendering.

[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: b98cd745-b0ae-47ea-9d50-9721f9cbcf50

📥 Commits

Reviewing files that changed from the base of the PR and between 6ed450a and bd7a562.

📒 Files selected for processing (2)

• code/core/src/controls/components/ControlsPanel.stories.tsx
• code/core/src/controls/components/ControlsPanel.tsx

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📝 Walkthrough

Walkthrough

This PR fixes the rendering behavior of ControlsPanel when stories belong to a composed ref. The component now determines its preview initialized state from the composed ref if applicable, rather than always using the host preview state. A regression test story validates the fix.

Changes

Composed Ref Preview Initialization

Layer / File(s)	Summary
Composed ref preview initialization logic code/core/src/controls/components/ControlsPanel.tsx	ControlsPanel reads storyData.refId and uses refs[refId].previewInitialized for composed ref stories, otherwise falls back to host previewInitialized. The useEffect that clears isLoading now depends on this computed isPreviewInitialized value.
Regression test story code/core/src/controls/components/ControlsPanel.stories.tsx	New story file mocks ManagerContext with host previewInitialized as false but composed ref's as true, then asserts the panel renders the expected control label text, validating the ref-based initialization works correctly.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

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[Sidnioulz]

Good job, that wasn't an easy one! Fix looks good to me, story renders well. 👏

I'm waiting for CI to be done. I've also launched a canary release workflow. Once it's over, there will be a comment at the bottom of the PR with the canary package's version.

Either you or I should check on the reproduction repo if, using that canary version, the problem is fixed. Feel free to do it if you have time before I do, and let me know how it goes :)

Once we've verified in the original repro repository, we can merge!

[Sidnioulz]

Note to self: Introduces a regression, see issue comments. If not fixed by release date, revert PR.