Bug: Unnecessary re-render

[behnammodi]

React version: 16.13.1

Steps To Reproduce

1- The first render is correct
2- The second re-render is correct because X changes from 1 to 2
3- The third re-render in the wrong

Link to code example:
https://codesandbox.io/s/bug-in-render-ldycb

The current behavior

The third re-render is unnecessary but happen

The expected behavior

The third re-render should not happen

[eps1lon]

Does this happen with the production build as well? I'm asking because it doesn't actually commit when transitioning from 2->2.

You can observe this wrapping the (side-effect) in useEffect:

React.useEffect(() => {
  console.log("render App", x);
})

[eps1lon]

Also: Probably a duplicate of #14994

[behnammodi]

@eps1lon Yes It's happen

[eps1lon]

Fairly certain this is a duplicate of #14994. Child won't re-render on the 2->2 transition: https://codesandbox.io/s/bug-in-render-ubppr?file=/src/index.js. There's some explanation in that thread for the current behavior.

[behnammodi]

@eps1lon Thanks, but every solution is awful.

[eps1lon]

@eps1lon Thanks, but every solution is awful.

I can understand why this might be undesired behavior for you. But this won't get solved by keeping duplicate issues open which require maintenance from the core team.

It also helps keeping the discussion focused so that potential workarounds aren't spread over the repository.

[behnammodi]

@eps1lon All right, I'll close it