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)

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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",)

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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.

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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....