useMutation - undocumented variables returned by useMutation

[mathieu-anderson]

I recently discovered that useMutation has variables in the list of returned values. Demo sandbox: https://codesandbox.io/s/relaxed-leftpad-nmuhxy?file=/src/App.js

My question is: why is it not documented here? https://tanstack.com/query/v4/docs/react/reference/useMutation

Should it not be used? We have a few use cases where it would come in handy. For example, in a list of buttons which all call the same mutate but with a different variable, it would be useful to know exactly which button should show a loading state when isLoading is true

[TkDodo]

You can use it, I'm not sure if I changed the behaviour slightly with v5, because what you are describing will be a first class pattern in v5:

https://tanstack.com/query/v5/docs/react/guides/optimistic-updates#via-the-ui

I just realised that I forgot to update the v5 reference docs to mention variables. If you want, you can contribute that to the alpha branch.

[mathieu-anderson]

Thank you! Which contribution would be desirable? Adding the variables returned value to the v5 useMutation docs? Or adding the pattern I described in the "Guides & Concepts" section? Or both? Or neither?

[TkDodo]

I think we have a good description in the guides already, so I'd appreciate it if you'd get the reference docs in a correct state 🙏

[mathieu-anderson]

Opened a PR against the alpha branch here: #5084