setState() in componentWillMount()

Avoid async initialization in componentWillMount()

componentWillMount() is invoked immediately before mounting occurs. It is called before render(), therefore setting state in this method will not trigger a re-render. Avoid introducing any side-effects or subscriptions in this method.

Make async calls for component initialization in componentDidMount instead of componentWillMount

function componentDidMount() {
  axios.get(`api/messages`).then((result) => {
    const messages = result.data;
    console.log('COMPONENT WILL Mount messages : ', messages);
    this.setState({
      messages: [...messages.content],
    });
  });
}