Django ModelAdmin - fieldsets ... field 'date' missing from the form

I figured out what the problem was while writing this question. I post it anyway in case it could help someone else.

The error: 'FooAdmin.fieldsets[0][1]['fields']' refers to field 'date' that is missing from the form.

With the following code:

# models.py
from django开发者_高级运维.db import models

class Foo(Base):
    date = models.DateField(auto_now_add=True)
    title = models.CharField(max_length=255)

# admin.py
from django.contrib import admin

class FooAdmin(BaseAdmin):
    list_display = ("title", "date")
    fieldsets = (
        (None, {
            "fields": ("date", "title")
        }),
    )

admin.site.register(Foo, FooAdmin)

The error is due to date having auto_now_add=True (or auto_now=True).
As the value is automatic, it's not editable, so it's not in the form. To solve that, add this in FooAdmin:

readonly_fields = ("date",)

My problem was actually a bit different. My problem involved model inheritence and the django.contrib.admin User model.

This caused the problem:

from django.utils.translation import ugettext_lazy as _
from django.contrib.auth.admin import UserAdmin
class AdminUser (UserAdmin):
    fieldsets = UserAdmin.fieldsets + (
        (_('APPS Info'), {'fields': ('agency', 'company')}),
    )

where "agency" and "company" are fields of my User model that extends django's user model. Your solution of putting those fields in readonly_fields did fix the error, but then those fields were read only, which isn't what I wanted. I found that the problem was that the ModelForm used in django.contrib.admin was setting the model to Django's user model. So to fix it I added this:

from django.contrib.auth.admin import UserAdmin, UserChangeForm as DjangoUserChangeForm
from django.utils.translation import ugettext_lazy as _
from apps_models.users.models import User
class UserChangeForm(DjangoUserChangeForm):
    class Meta:
        model = User
class AdminUser (UserAdmin):
    fieldsets = UserAdmin.fieldsets + (
        (_('APPS Info'), {'fields': ('agency', 'company')}),
    )
    form = UserChangeForm

That's what I get for using Model inheritance... it isn't pretty, but it got the job done.

So it sounds like we were getting the same error, but for different reasons.

It may also help some people to know the error also appears when there are incorrect fieldsets in the ModelAdmin, ...as when doing migrations and forgetting to delete removed fields....