componentWillMount renamed ⚛️ React

Warning: componentWillMount has been renamed, and is not recommended for use.

A class component uses legacy lifecycle methods (componentWillMount/WillReceiveProps/WillUpdate).

Seen on: React

Meaning

These lifecycles are unsafe for async rendering. React prints the warning with the component names.

Common causes

  • Old class components
  • Outdated libraries

⚡ Quick fix

  1. Move logic to componentDidMount / getDerivedStateFromProps / componentDidUpdate
  2. Upgrade libraries
  3. Run npx react-codemod rename-unsafe-lifecycles as a stopgap

Detailed fix by platform

React

  1. Convert to function components with useEffect where possible

How to diagnose

  1. Components — Which are listed?
  2. Recent change — Did it start after a deploy, upgrade, or configuration change? Compare with the last working version.

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