Better error message when filtering users with AnonymousUser

[Sveder]

When trying to filter a model with User ForeignKey on AnonymousUser, we get a cryptic:
Exception Value: int() argument must be a string or a number, not 'AnonymousUser'

For example:
​https://stackoverflow.com/questions/3439709/how-to-cater-for-anonymoususer-when-filtering-based-on-user

I think this deserves a better error message, for example something like:
ValueError("Can't filter User field with AnonymousUser").

[Carlton Gibson]

Yep. Great. Better error messages FTW! 🙂

[Ramon Saraiva]

Still trying to understand what piece of code would be responsible for this behaviour.
I wonder if overwriting AnonymousUser's __int__ would be too naive?

Since AnonymousUser is not inheriting from Model, it happens that its instance is passed all the way over to the field get_prep_value and then int(value -> AnonymousUser) is called.
Any guidance/idea about what should be responsible for doing this validation?

[Tim Graham]

An obvious implementation doesn't come to mind. I'm not sure if it's feasible.

[Adam Johnson]

{{AnonymousUser.int}} might work, if you make the error message more generic like {{TypeError("Cannot cast AnonymousUser to int. Are you trying to use it in place of User?")}}

[Ramon Saraiva]

Ok, I'll work on that patch and we can continue from there.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 2349cbd9:

Fixed #29782 -- Added better error message when filtering queryset with AnonymousUser.