name: dev.cds-web description: USE THIS when asked to work on a new or existing (WEB) CDS React component in packages/web

CDS Web Package Guidelines

Component Config Adoption (Web)

Use this guidance when adding ComponentConfigProvider defaults for the specific component you are editing.

Required implementation pattern

1. Register the component in packages/web/src/core/componentConfig.ts using its *BaseProps:

import type { MyComponentBaseProps } from '../category/MyComponent';

export type ComponentConfig = {
  MyComponent?: ConfigResolver<MyComponentBaseProps>;
};

1. Adopt useComponentConfig in the component and destructure from merged props:

import { useComponentConfig } from '../hooks/useComponentConfig';

export const MyComponent = memo((_props: MyComponentProps) => {
  const mergedProps = useComponentConfig('MyComponent', _props);
  const { className, style, ...props } = mergedProps;

  return <Box className={className} style={style} {...props} />;
});

Rules to preserve behavior

• Provider config supplies defaults only; local props must continue to win.
• Use _props as the input variable and mergedProps as the configured output.
• Type resolver entries with *BaseProps (not polymorphic/full *Props).
• Keep scope to prop-level theming defaults; do not alter component behavior or control flow.
• When practical during the same change, prefer arrow-function component declarations.

CSS with Linaria

Use Linaria for zero-runtime CSS. Always use CDS theme CSS variables for colors, spacing, typography, and other design tokens. Reference packages/web/src/core/theme.ts:53-119 for the CSS variable naming pattern.

import { css, cx } from '@linaria/core';

const containerCss = css`
  /* Spacing tokens */
  padding: var(--space-2);
  gap: var(--space-1);

  /* Color tokens */
  background: var(--color-bgPrimary);
  color: var(--color-fgPrimary);
  border: 1px solid var(--color-line);

  /* Border radius tokens */
  border-radius: var(--borderRadius-400);

  /* Typography tokens */
  font-size: var(--fontSize-body);

  &:hover {
    background: var(--color-bgPrimaryHover);
  }
`;

// Merge classNames with cx utility **in CORRECT ORDER**
<div
  className={cx(
    containerCss, // Base styles first
    isCompact && conditionClassToApply, // Conditional computed styles
    className, // User-provided className prop
    classNames.root, // granular overrides last
  )}
/>;

IMPORTANT: Using CSS variables ensures components respond correctly to theme changes (light/dark mode, brand themes).

CSS Variable Naming

Design tokens from packages/common/src/core/theme.ts map to CSS variables:

• Colors: --color-{tokenName} (e.g., --color-bgPrimary, --color-fgMuted)
• Spacing: --space-{scale} (e.g., --space-2 = 16px, --space-3 = 24px)
• Typography: --fontSize-{font}, --fontWeight-{font}, --lineHeight-{font}, --fontFamily-{font}
• Border: --borderRadius-{size}, --borderWidth-{size}
• Sizing: --iconSize-{size}, --avatarSize-{size}, --controlSize-{name}
• Shadows: --shadow-{level}

Responsive Breakpoints

Reference packages/web/src/styles/media.ts for breakpoint values:

• phone: 0-767px
• tablet: 768-1279px
• desktop: 1280px+

Use the Box component's responsive prop API for responsive values:

<Box padding={{ base: 2, phone: 1, desktop: 3 }} />

Granular classNames

• Components can expose a classNames object prop for granular overrides on child elements within the component.
• Since the keys of the classNames object are specific to the component they should never be on the *BaseProps type

data-attributes

• Use data attributes for state-based styling: data-active, data-disabled, data-variant, data-filled

Inline styles

• Web components should all expose a style and styles object props for overriding inline styles.
• As styling is a concern of that specific component, the style and styles props should never be on the *BaseProps type.
• Styles should be merged into a single object with a useMemo hook and applied in the correct order (default styles => style prop => styles[ELEMENT_NAME] prop).

Example:

type ComponentProps = ComponentBaseProps & {
  style?: React.CSSProperties;
  styles?: { root?: React.CSSProperties; label?: React.CSSProperties };
};

Animation

Use Framer Motion for complex animations:

import { m as motion, AnimatePresence } from 'framer-motion';

<AnimatePresence>
  {visible && (
    <motion.div
      initial={{ opacity: 0, y: -8 }}
      animate={{ opacity: 1, y: 0 }}
      exit={{ opacity: 0, y: -8 }}
    />
  )}
</AnimatePresence>;

For simple transitions, prefer CSS transitions in Linaria.

Accessibility

Use ARIA attributes:

<div role="group" aria-roledescription="carousel" aria-live="polite">
  <button aria-pressed={isActive} tabIndex={isVisible ? 0 : -1} />
</div>

• Implement keyboard navigation (Arrow keys, Home, End) for interactive components.
• Provide descriptive labels for all interactive elements
• Associate form inputs with helper text using aria-describedby
• Use semantic HTML elements whenever possible
• Follow WCAG 2.1 AA standards for color contrast
• Support screen readers by providing descriptive labels and instructions

Web-Specific Props

• className?: string - CSS class always applied to root element
• style?: React.CSSProperties - inline styles always applied to root element
• Polymorphic as prop for element type (where applicable e.g. see Box)

Reference Components

• Carousel: compound components, imperative handle, context pattern
• Select (alpha/): generics, controlled/uncontrolled
• RollingNumber: animation config, measurement patterns