Empty text fields and "" vs null

What you were expecting:

I have a couple of forms with textfields.

An example openapi spec would be:

Person:
  required:
    - name
  type: object
  properties:
    name:
      type: string
   nickname:
      type: string

Here is what i would expect:

create:

name: "michael", nickname: "" => {name: "michael"}
name: "michael", nickname: "mick" => {name: "michael", nickname: "mick"}

update

name: "michael", nickname: "" => {name: "michael", nickname: ""}
name: "michael", nickname: "mick" => {name: "michael", nickname: "mick"}

What happened instead:

When "nickname" was empty, in the request object "nickname" was set to null. this is documented behavior: https://github.com/marmelab/react-admin/blob/master/docs/SimpleForm.md#sanitizeemptyvalues and it is stated that this is expected by most backends. https://github.com/marmelab/react-admin/blob/032e1464cd23cf15dbc4d641e9663f74b37b9563/packages/ra-core/src/form/useInput.ts#L23-L24

From my understanding, this is how an optional text-field would be handled in a backend

not present in the object => optional => don't touch it
empty string "" => set the value as an empty string
any other string => set the value.

So it might make sense to remove the value from the object when the state has not changed, but to make it null when it is empty feels a bit counter-intuitive to me. In pydantic for example this would be an error:

Also this reads to me as it would be preferable to use an empty string: https://stackoverflow.com/questions/45575493/what-does-required-in-openapi-really-mean

This seems to be a choice made by react-admin dev's and that*s okay, but I would like to get your motivation on this and maybe you can point me to the backends that implemented this in that particular way?

I will also send a pull-request to update the docs with an example if that's okay.

related issues/prs

https://github.com/marmelab/react-admin/pull/8188 https://github.com/marmelab/react-admin/pull/8262

https://github.com/marmelab/react-admin/issues/8472

Environment

React-admin version: 4.6.0
Last version that did not exhibit the issue (if applicable): 4.2.2
React version: 17
Browser: recent firefox & chrome
Stack trace (in case of a JS error):

marmelab / react-admin

Empty text fields and "" vs null #8537