Hiding field deletes form values

[tdeo]

What you were expecting:
When upgrading to version 3 beta, I expected the forms to keep values even when fields are mounted / unmounted.

What happened instead:
If a form field is unmounted, the value of the field is removed from the form state. This is especially a problem in dynamic field and when displaying part of a form inside a modal.

Steps to reproduce:
Set up a field displayed based on another value as the doc mention (https://github.com/marmelab/react-admin/blob/next/docs/Inputs.md#linking-two-inputs), then when the condition changes and the field gets unmounted / remounted, it doesn't have a value anymore.

Related code:
https://codesandbox.io/s/vibrant-tereshkova-q6i27
Pick a user, enable the email toggle, the original email is present.
After disabling / enabling the toggle again, the email address is gone from the field:

Other information:
It looks like this is due to some internals of react-final-form, I didn't have time to investigate though.

It would be nice to figure a workaround, I'll update the issue if I can figure something out.

Environment

• React-admin version: 3.0.0-beta.3
• Last version that did not exhibit the issue (if applicable): 2
• React version: 16.8.6
• Browser: Chrome
• Stack trace (in case of a JS error): N/A

[fzaninotto]

Reproduced and confirmed, thanks for the CodeSandbox. I suspect this is a react-final-form bug, would you mind opening an issue in their bug tracker?

[tdeo]

It doesn't seem to be reproducible with final-form only: https://codesandbox.io/s/kind-jang-0gyjg

[fzaninotto]

Thanks. Your last example is simpler than what we do in react-admin (you should use the same subscriptions and use a FormSpy), but I appreciate the effort. I'll dig further to try and understand what react-admin does wrong here.

[tdeo]

@fzaninotto I actually was trying out with the simple example and realized it's the destroyOnUnregister prop of <Form> in SimpleForm.js that causes the issue

Edit: It looks like in the migration from redux-form to final-form (306aef5), redux-form's destroyOnUnmount was migrated to final-form destroyOnUnregister which don't have the same effect

[fzaninotto]

Exactly, so I think #3884 should fix the problem. I'm going to test that patch more thoroughly.

[fzaninotto]

Fixed by #3884

[tdeo]

👍 Thanks