Bug: too hard to fix "Cannot update a component from inside the function body of a different component."

Note: React 16.13.1 fixed some cases where this was overfiring. If upgrading React and ReactDOM to 16.13.1 doesn’t fix the warning, read this: https://github.com/facebook/react/issues/18178#issuecomment-595846312

---

React version:

16.13.0

Steps To Reproduce

1. Build a time machine.
2. Go to the year 2017.
3. Build a huge application of 10K lines of code.
4. Get 80 (!) dependencies at package.json file including ones that become no longer maintained.
5. Update React to the latest version at February 27, 2020.
6. Get tons of errors that you don’t know how to fix.
7. Tell your client that fixes are going to take unknown time and it’s going to cost $$$ + days or weeks of investigation or we’re going to get stuck with the outdated version of React and related libraries forever which will cost more $$$ but later.

Being serious, the business I work for isn’t interested on that at all. Obviously I’d never made it happen to get such warnings to appear if I’d get them earlier. Currently that’s impossibly hard to make the errors to be fixed because I get them at many different cases and with a huge stack trace. I tried to fix at least one of the appearing errors and it already took a lot of time. I tried to debug some of used libraries but got no luck.

Just one example:

There we can notice the use of an outdated react-router, an outdated redux-connect (which I had to put to the project source to fix errors of outdated componentWillReceiveProps method), some HOCs created by recompose etc. It isn’t just a simple virtual DOM tree where I can walk thru components developed by me and search by setState string to fix the bug, that’s way more complicated than that.

Please make an “UNSAFE” option to disable this error or provide a simpler way to find where the error is thrown 🙏

[gaearon]

To the future commenters. I understand seeing a new warning is frustrating. But it points out legitimate issues that are likely causing bugs in your code. We would very much appreciate if you could refrain from expressing sarcasm and annoyance.

If you can’t understand where it’s coming from in the stack traces, please post screenshots or create reproducing sandboxes and we’ll try to help. Most of these are probably coming from a few libraries, so the most productive thing to do is to reduce these cases and then file issues with those libraries.

Thank you all.

[gaearon]

We fixed the cases where the warning was over-firing in 16.13.1. The remaining cases are legit and need to be fixed.