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composition-patterns skill

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This skill guides refactoring with composition patterns to replace boolean props, enabling scalable, reusable React APIs and architecture.

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SKILL.md

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---
name: vercel-composition-patterns
description:
  React composition patterns that scale. Use when refactoring components with
  boolean prop proliferation, building flexible component libraries, or
  designing reusable APIs. Triggers on tasks involving compound components,
  render props, context providers, or component architecture. Includes React 19
  API changes.
license: MIT
metadata:
  author: vercel
  version: '1.0.0'
---

# 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()`

## How to Use

Read individual rule files for detailed explanations and code examples:

```
rules/architecture-avoid-boolean-props.md
rules/state-context-interface.md
```

Each rule file contains:

- Brief explanation of why it matters
- Incorrect code example with explanation
- Correct code example with explanation
- Additional context and references

## Full Compiled Document

For the complete guide with all rules expanded: `AGENTS.md`

Overview

This skill provides a curated set of React composition patterns that scale for component libraries and large apps. It helps you refactor components that suffer from boolean prop proliferation and design clearer, more maintainable APIs using compound components, providers, and modern React 19 considerations. The guidance focuses on practical refactors that make components easier for both humans and AI to reason about.

How this skill works

The skill inspects component design tasks and suggests rule-driven refactors such as replacing boolean props with explicit variant components, lifting state to providers, and structuring compound components around shared context. It flags architecture issues by priority (architecture, state, implementation patterns, React 19 APIs) and offers concrete patterns and code-level recommendations to implement each rule. Use it when reviewing or evolving component APIs to improve reuse and testability.

When to use it

Refactoring components with many boolean props that control behavior
Designing or maintaining a shared component library or design system
Implementing compound components that share state across children
Reviewing component architecture or onboarding contributors
Adopting React 19 APIs or modernizing context/state usage

Best practices

Avoid boolean props for mode switches; create explicit variant components instead
Lift shared state into a provider so sibling components can access and modify it
Encapsulate implementation details inside provider components; expose a small, typed interface
Prefer children composition and context over scattered render props or ad-hoc props
Follow clear rule priorities: fix architecture first, then state, then implementation details

Example use cases

Refactor a Toggle with dozens of boolean flags into a ToggleProvider and explicit Toggle.On/Toggle.Off children
Create a Modal library that exposes Modal, ModalHeader, ModalBody using shared context for open/close state
Replace a Button with boolean props like primary/secondary/ghost by exporting explicit PrimaryButton and GhostButton variants
Migrate code to React 19 by removing forwardRef-heavy patterns and adapting to updated hooks and context practices
Standardize state interfaces with {state, actions, meta} for easier dependency injection and testing

FAQ

Should I always remove boolean props?

Not always; boolean props are fine for trivial toggles. Prefer removing them when they multiply and create combinatorial complexity or when clearer explicit variants improve readability and API discoverability.

Does this require React 19?

No. Most patterns apply to any modern React version. React 19-specific recommendations are optional and only relevant when you upgrade to that runtime.