Server validation errors not removed after field change

[fzan]

What you were expecting:

After this merged PR
#5778
I'm expecting that, after an error is returned from server, it will be shown on the field.
That error must disappear after the field value change, because it must be checked again on the server to validate

What happened instead:

After an error is returned from server, it appears correctly on the related field.
But that error remains after the field value change, leaving the field in error state

Steps to reproduce:

1. Add an error handler like this suggested in documentation:
   https://marmelab.com/react-admin/CreateEdit.html#submission-validation
2. Having a requested field on server, leave it blank, submit the form and trigger the error.
3. The field is now correctly in error state
4. Try to change the content
5. The fields remain in error state
6. Fill the server-side required field
7. If you submit now, with the required field filled, the form gets submitted correctly, but an error snackbar opens (because there are errors on the form on the submission time)
   Environment

• React-admin version: 3.12.4
• React version: 16.13.1
• Browser: Chrome 88.0.4324.150 on Windows 10

[alanpoulain]

Hello,
You need to use https://github.com/ignatevdev/final-form-submit-errors, like it's done in API Platform Admin:
https://github.com/api-platform/admin/blob/5badc1f19024c1800a60431e575219039b86d0b6/src/CreateGuesser.js#L134-L153

React admin could use it by default too, but it needs to be discussed.

[fzan]

@alanpoulain your support was absolutely outstanding!
Thanks for pointing me to the right direction!

[fzaninotto]

@alanpoulain Agreed, this should be by default in react-admin. Would you like to open a PR about it?

[fzan]

Hello, sorry to bump this, but i have a question.

The validation errors are shown 1:1 with the field, and that's the expected behaviour and an excellent solution.
However, imagine a form with:
SelectInput A: select the type of next item ( Int, string)
TextInput B: the value regarding the type choosed on input A

Well, now try to imagine that i submit:

A: Type Int
B: value "hello"
and submit.

The server reply with an error on the TextInput B "value not valid".
Now, instead of changing the TextInputB, i change the SelectInput A, to "string"

The error shown on TextInput B is still there, so on submit i will get a correct save, because the form is in a correct state, but because the field is still in error state, i will also get an error in the snackbar.

What do you think about it? @alanpoulain