system checks: admin.E002 could provide a hint but doesn't

[Keryn Knight]

Currently the output is:

myapp.MyCustomUserModel: (auth.E002) The field named as the 'USERNAME_FIELD' for a custom user model must not be included in 'REQUIRED_FIELDS'.

because I accidentally had:

USERNAME_FIELD = "email"
EMAIL_FIELD = "email"
REQUIRED_FIELDS = (USERNAME_FIELD, "full_name",)

Ignoring the fact that Django knows it's wrong to have it in there, and could easily just skip it or warn if it's not set, it doesn't make use of the hints available in system checks.

I'd like to suggest that a hint could be provided which says which field it's moaning about, something like (open to better wording):

HINT: Your username field is currently set to "email", you should remove "email" from your required fields definition.

It's a stupidly little thing, but having not had to make a custom user from scratch for a while, my eyes glazed over the not in must not be and I was confused for all of 2 minutes before actually reading it properly.

[Carlton Gibson]

OK, fair enough. Got bandwidth for a patch?

[Mariusz Felisiak]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In fba5d3b6:

Fixed #31289 -- Added hint for USERNAME_FIELD/REQUIRED_FIELDS system check.