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react19-source-patterns

Reference for React 19 source-file migration patterns, including API changes, ref handling, and context updates.

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Use react19-source-patterns to migrate [React source files] to React 19 patterns, addressing applicable rendering, ref, context, and default-prop changes while retaining propTypes with the required explanatory comment.

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SKILL.md

name: react19-source-patternsdescription: 'Reference for React 19 source-file migration patterns, including API changes, ref handling, and context updates.'

React 19 Source Migration Patterns

Reference for every source-file migration required for React 19.

Quick Reference Table

Pattern	Action	Reference
`ReactDOM.render(...)`	→ `createRoot().render()`	See references/api-migrations.md
`ReactDOM.hydrate(...)`	→ `hydrateRoot(...)`	See references/api-migrations.md
`unmountComponentAtNode`	→ `root.unmount()`	Inline fix
`ReactDOM.findDOMNode`	→ direct ref	Inline fix
`forwardRef(...)` wrapper	→ ref as direct prop	See references/api-migrations.md
`Component.defaultProps = {}`	→ ES6 default params	See references/api-migrations.md
`useRef()` no arg	→ `useRef(null)`	Inline fix add `null`
Legacy Context	→ `createContext`	→ api-migrations.md#legacy-context
String refs `this.refs.x`	→ `createRef()`	→ api-migrations.md#string-refs
`import React from 'react'` (unused)	Remove	Only if no `React.` usage in file

PropTypes Rule

Do not remove .propTypes assignments. The prop-types package still works as a standalone validator. React 19 only removes the built-in runtime checking from the React package the package itself remains valid.

Add this comment above any .propTypes block:

// NOTE: React 19 no longer runs propTypes validation at runtime.
// PropTypes kept for documentation and IDE tooling only.

Read the Reference

For full before/after code for each migration, read references/api-migrations.md. It contains the complete patterns including edge cases for forwardRef with useImperativeHandle, defaultProps null vs undefined behavior, and legacy context provider/consumer cross-file migrations.