form fields with different type but no key get reused when re-rendering about react

[gaearon]

It's described in more detail here: https://react.dev/learn/preserving-and-resetting-state

I agree it's not immediately obvious. The canonical solution for your case is to extract components like SettingsForm / SignupForm, for example.

It might be a good idea to mention it in "conditional rendering" but I'm worried it's a bit much at that stage.

[johtso]

@gaearon thanks for the thoughtful reply!

This section definitely covers these issues: https://react.dev/learn/preserving-and-resetting-state#resetting-state-at-the-same-position

The only thing that doesn't seem clear to me is what is considered the identity of a native element. "when you render a different component in the same position, it resets the state of its entire subtree"

Intuitively you'd think that different types of input/button element would be considered different for the purposes of rendering. If it's literally just the element that's taken into consideration, then maybe the page could mention that and when that might be surprising (maybe using submit/button buttons as an example).

Hope this input is helpful!

[johtso]

@gaearon also, this was the use case:

Untitled.mov

https://gist.github.com/johtso/df763fbe9d9f50967e94e007f3091d42

There's obviously lots of ways I could have modelled this that wouldn't have stumbled into this issue. I could have just hidden the password field instead of not rendering it, and used a value on the submit button to help the server distinguish the type of login.

To be honest I'm still not clear on how React models the "tree" to decide if a element is in the same place as a previous element. Looking at my implementation I still don't see why the presence of the password input field affects the identity / position in the tree of the two buttons.