@diskette/composed-props

A TypeScript-first React hooks library that enables component libraries to provide render props functionality with type inference and runtime validation.

📦 Installation

npm install @diskette/composed-props

yarn add @diskette/composed-props

pnpm add @diskette/composed-props

Key Features

• 🏭 Hook Factory Pattern: Create customized useRenderProps hooks tailored to your component's needs
• 🔒 Type Safety: Sophisticated TypeScript inference with runtime validation
• 🎯 Component Library Focus: Built specifically for library authors to expose render props APIs
• 🌟 Multi-State Support: Different props can respond to different state types
• 🔧 Flexible: Support for static values, dynamic functions, defaults, and transforms

🧩 Core Concepts

ComposableProp<T, V>

The ComposableProp<T, V> type represents a prop that can be either:

• A static value of type V
• A function (state: T) => V that computes the value from component state

import type { ComposableProp } from '@diskette/composed-props'

interface ButtonState {
  isHovered: boolean
  isPressed: boolean
}

interface ButtonProps {
  // Must explicitly use ComposableProp for each prop
  backgroundColor: ComposableProp<ButtonState, string>
  opacity: ComposableProp<ButtonState, number>
  // Non-composable props remain normal
  onClick?: () => void
}

// Static usage
<Button backgroundColor="#007bff" opacity={1} />

// Dynamic usage
<Button
  backgroundColor={({ isHovered, isPressed }) =>
    isPressed ? '#0056b3' : isHovered ? '#0069d9' : '#007bff'
  }
  opacity={({ isHovered }) => isHovered ? 0.8 : 1}
/>

📚 API Reference

createUseRenderProps<Config>(config)

Creates a type-safe useRenderProps hook based on a configuration schema. This is the primary tool for component library authors.

Example: Creating a Custom Hook

import { createUseRenderProps } from '@diskette/composed-props'
import type { ComposableProp } from '@diskette/composed-props'

// Define your component's state shapes
interface TabsState {
  activeTab: string
  hoveredTab: string | null
}

interface ThemeState {
  theme: 'light' | 'dark'
}

// Props interface using ComposableProp explicitly
interface TabsProps {
  className?: ComposableProp<TabsState, string>
  style?: ComposableProp<ThemeState, CSSProperties> // Different state type!
  'data-active': ComposableProp<TabsState, boolean> // Required prop
  children?: ComposableProp<TabsState, ReactNode>
  // Non-composable props
  onTabChange?: (tab: string) => void
}

// Create the hook factory with validation
const useTabsRenderProps = createUseRenderProps({
  className: { type: 'string' },
  style: { type: (value): value is CSSProperties => typeof value === 'object' },
  'data-active': { type: 'boolean', required: true },
  children: { type: (value): value is ReactNode => true },
})

// Component library implementation
function Tabs(props: TabsProps) {
  const [activeTab, setActiveTab] = useState('tab1')
  const [hoveredTab, setHoveredTab] = useState<string | null>(null)
  const [theme, setTheme] = useState<'light' | 'dark'>('light')

  const tabsState: TabsState = { activeTab, hoveredTab }
  const themeState: ThemeState = { theme }

  const { composed, rest } = useTabsRenderProps(props)

  // Option 1: Use individual functions
  const className = composed.className?.(tabsState)
  const style = composed.style?.(themeState)

  return (
    <div
      className={className}
      style={style}
      data-active={composed['data-active']?.(tabsState)}
      {...rest}
    >
      {composed.children?.(tabsState)}
    </div>
  )

  // Option 2: Use props helper with multi-state support
  // const resolvedProps = composed.props({
  //   className: tabsState,    // TabsState for className
  //   style: themeState,       // ThemeState for style (different state!)
  //   'data-active': tabsState, // TabsState for data-active
  //   children: tabsState      // TabsState for children
  // })
  //
  // return <div {...resolvedProps} />  // rest is already included!
}

Individual Functions vs Props Helper

const { composed, rest } = useAccordionRenderProps(props, {
  // Options for defaults and transforms
  duration: {
    default: ({ isExpanded }) => (isExpanded ? 300 : 200),
  },
  className: {
    transform: (className, { isAnimating }) =>
      isAnimating ? `${className} accordion--animating` : className,
  },
})

// Approach 1: Individual functions (fine-grained control)
const className = composed.className?.(accordionState)
const style = composed.style?.(themeState)
const duration = composed.duration?.(accordionState)

return (
  <div className={className} style={style} data-duration={duration} {...rest}>
    {composed.children?.(accordionState)}
  </div>
)

// Approach 2: Props helper
const resolvedProps = composed.props({
  className: accordionState,
  style: themeState, // Different state type for style!
  duration: accordionState,
  children: accordionState,
})

return <div {...resolvedProps} /> // rest already included