Vercel composition patterns

React Composition Patterns

Composition patterns for building flexible, maintainable React components. Avoid boolean prop proliferation by using compound components, lifting state, and composing internals. These patterns make codebases easier for both humans and AI agents to work with as they scale.

When to Apply

Reference these guidelines when:

• Refactoring components with many boolean props
• Building reusable component libraries
• Designing flexible component APIs
• Reviewing component architecture
• Working with compound components or context providers

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Component Architecture	HIGH	architecture-
2	State Management	MEDIUM	state-
3	Implementation Patterns	MEDIUM	patterns-
4	React 19 APIs	MEDIUM	react19-

Quick Reference

1. Component Architecture (HIGH)

• architecture-avoid-boolean-props - Don't add boolean props to customize behavior; use composition
• architecture-compound-components - Structure complex components with shared context

2. State Management (MEDIUM)

• state-decouple-implementation - Provider is the only place that knows how state is managed
• state-context-interface - Define generic interface with state, actions, meta for dependency injection
• state-lift-state - Move state into provider components for sibling access

3. Implementation Patterns (MEDIUM)

• patterns-explicit-variants - Create explicit variant components instead of boolean modes
• patterns-children-over-render-props - Use children for composition instead of renderX props

4. React 19 APIs (MEDIUM)

⚠️ React 19+ only. Skip this section if using React 18 or earlier.

• react19-no-forwardref - Don't use forwardRef; use use() instead of useContext()

Core Principle

Avoid boolean prop proliferation. When a component accumulates boolean props like isLarge, isLoading, hasIcon, showFooter, it becomes a configuration panel instead of a component. This pattern:

• Makes the API surface impossible to understand at a glance
• Creates combinatorial state explosions (2^n possible states for n booleans)
• Prevents tree-shaking and dead code elimination
• Makes AI-assisted refactoring much harder

Instead, compose. Create explicit variant components, lift state into providers, and use children for flexible content injection.

Example: Boolean Props → Composition

// ❌ Boolean prop proliferation
<Button isLarge isLoading hasLeftIcon={<IconSpinner />} disabled={isLoading}>
  Submit
</Button>

// ✅ Explicit variants + composition
<Button.Large disabled={isLoading}>
  {isLoading ? <Spinner /> : null}
  Submit
</Button.Large>

Compound Component Pattern

// Provider holds shared state
function Tabs({ children, defaultTab }) {
  const [active, setActive] = useState(defaultTab);
  return (
    <TabsContext.Provider value={{ active, setActive }}>
      {children}
    </TabsContext.Provider>
  );
}

// Children consume via context
Tabs.Tab = function Tab({ id, children }) {
  const { active, setActive } = useContext(TabsContext);
  return (
    <button
      onClick={() => setActive(id)}
      aria-selected={active === id}
    >
      {children}
    </button>
  );
};

// Usage is readable and composable
<Tabs defaultTab="overview">
  <Tabs.Tab id="overview">Overview</Tabs.Tab>
  <Tabs.Tab id="details">Details</Tabs.Tab>
</Tabs>