Bug: after upgrade v18 "componentDidMount" run twice, and componentWillUnmount also run when component mounting

[awefeng]

React version: v18.0.0

Steps To Reproduce

1. write a class component
2. write "componentDidMount" and "componentWillUnmount" lifecycle functions,log a tip

   componentDidMount() {
   console.log("componentDidMount");
   }
   componentWillUnmount() {
   console.log("componentWillUnmount");
   }

Link to code example: https://codesandbox.io/s/stoic-snowflake-pwih7o

The current behavior

the console print componentDidMount ->componentWillUnmount -> componentDidMount

The expected behavior

only run componentDidMount once

[awefeng]

this is a v17.0.2 example https://codesandbox.io/s/runtime-brook-z67gx3

[GLObus303]

That's a new behaviour inside StrictMode - https://reactjs.org/blog/2022/03/29/react-v18.html#new-strict-mode-behaviors

[gaearon]

Yes, this is a development-only change in Strict Mode described here. You can opt out of Strict Mode while upgrading if this breaks your code and then fix the issues later.

https://reactjs.org/blog/2022/03/29/react-v18.html#new-strict-mode-behaviors

[awefeng]

That's a new behaviour inside StrictMode - https://reactjs.org/blog/2022/03/29/react-v18.html#new-strict-mode-behaviors

maybe I should take a good look at the update docs，thank you bro

[awefeng]

Yes, this is a development-only change in Strict Mode described here. You can opt out of Strict Mode while upgrading if this breaks your code and then fix the issues later.

https://reactjs.org/blog/2022/03/29/react-v18.html#new-strict-mode-behaviors

thank you bro