Provide ability to leverage CSS variables for status values provided by Vitest

[JamesIves]

Closes #31462

What I did

Attaches CSS variables to status values, with fallbacks to their existing values. This allows things to work as-is with the ability to change them based on needs.

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!

1. Set the CSS variable on the class provided to the button.
2. When the tests error you'll now see the updated color.

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

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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

Based on the provided information, I'll create a concise summary of the PR changes:

Introduces CSS variables for status value colors in the Storybook UI's sidebar, focusing on warning and error states to improve accessibility and theme customization.

• Added --status-value-color-warning CSS variable with fallback to #A15C20 in code/core/src/manager/utils/status.tsx
• Added --status-value-color-error CSS variable with fallback to brown in code/core/src/manager/utils/status.tsx
• Maintains backward compatibility through fallback values for existing implementations
• Addresses color contrast accessibility issues in the sidebar for Vitest addon status indicators

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[greptile-apps]

LGTM

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[nx-cloud]

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☁️ Nx Cloud last updated this comment at 2025-05-12 17:21:01 UTC

[ghengeveld]

Hi @JamesIves,

Our theming system is currently not built around CSS variables but rather the Emotion ThemeProvider. We have plans to switch to a system based on CSS variables, hopefully this fall. If you have ideas or opinions around this I would love to get your feedback on that RFC.

Regarding this PR, I would rather not merge it as-is because it doesn't align with current practices and also makes it harder to holistically switch to CSS variables later. The proper solution (for now) would be to swap the CSS color strings for a color theme variable keys (probably warning and negative, see here), then have the components that use this value look it up from the theme. If needed, the components can use CSS color mixing to adjust for better contrast. It's more convoluted so I don't love it, but it's what fits the system we have.

[JamesIves]

Is the warning theme colour something I can provide via the theme object? I'm really just looking for a way I can select the warning/error state so I can override it with my own variable.

[ghengeveld]

@JamesIves Yes, you can override theme colors. Here's an example Storybook that does this.

[ghengeveld]

@JamesIves are you able to style this by overriding theme colors like I suggested? I would rather just close this PR if it's not strictly necessary, so we don't clobber any future work surrounding CSS variables (we have plans to leverage them for Theming 2.0).

[JamesIves]

No because you can't pass a CSS variable to a Storybook theme. I swap out the variable set based on a theme switcher which allows me to theme the entire Storybook UI based on what theme is currently selected.

If there's future work surrounding variables then that sounds like a better long-term fix.

[ghengeveld]

Closing in favor of #32042
We will address customizability as part of the Theming 2.0 project later.

[XavierMP14]

AWESOME