[bedrich-schindler]

Class name helpers now return undefined instead of null when no class applies, and the rule is documented in the API Guidelines.
Closes #695

[github-actions]

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2026-10-20 13:42 UTC

[adamkudrna]

So this is a unification with the props approach, right?

[bedrich-schindler]

So this is a unification with the props approach, right?

Yes. Side effect is that also fixed my statement from the #695:

The reason is simple. Output of those class name helpers are forwarded to ‘className’ prop. It can be passed into classNames() that transforms it to undefined anyway. But it can also be used directly as single class name and then we need to handle those situations because null is transformed to class. Undefined means that it is omit at all

[Copilot]

Copilot review overview

🟡 Changes recommended

The changed fallback contract lacks the repository-required regression tests.

Review effort: Balanced
Findings: 1

Open (1)

• Add regression tests for helper no-match fallback results · New

What changed in this PR

Updates class-name helpers to return undefined, matching React’s className type and API conventions.

Changes:

• Replaces null fallbacks across ten class-name helpers.
• Documents empty-value conventions.
• Regression tests are missing.

File	Description
src/​docs/​contribute/​api.md	Documents empty-value rules.
src/​components/​Text/​_helpers/​getRootWordWrappingClassName.ts	Returns undefined when unset.
src/​components/​Text/​_helpers/​getRootHyphensClassName.ts	Returns undefined when unset.
src/​components/​Text/​_helpers/​getRootClampClassName.ts	Returns undefined when unset.
src/​components/​Modal/​_helpers/​getScrollingClassName.ts	Returns undefined when unset.
src/​components/​Modal/​_helpers/​getPositionClassName.ts	Returns undefined when unset.
src/​components/​Button/​helpers/​getRootLabelVisibilityClassName.ts	Returns undefined when unset.
src/​components/​_helpers/​getRootValidationStateClassName.ts	Returns undefined when unset.
src/​components/​_helpers/​getRootSizeClassName.ts	Returns undefined when unset.
src/​components/​_helpers/​getRootPriorityClassName.ts	Returns undefined when unset.
src/​components/​_helpers/​getRootColorClassName.ts	Returns undefined when unset.

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