Sorry, that's just a red herring from writing up the bug report. Here is a real example from right now:
In [1]: from case.models import Case
In [2]: case = Case.objects.get(id=REDACTED)
In [3]: case.content_object
Out[3]: <REDACTED: REDACTED>
In [4]: case.content_type_id = 175
In [5]: case.object_id = '218-555-1212'
In [6]: case.content_object
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
File /srv/www/testing/lib/.venv/lib/python3.10/site-packages/django/db/models/fields/__init__.py:1836, in IntegerField.to_python(self, value)
1835 try:
-> 1836 return int(value)
1837 except (TypeError, ValueError):
ValueError: invalid literal for int() with base 10: '218-555-1212'
During handling of the above exception, another exception occurred:
ValidationError Traceback (most recent call last)
Cell In[6], line 1
----> 1 case.content_object
File /srv/www/testing/lib/.venv/lib/python3.10/site-packages/django/contrib/contenttypes/fields.py:233, in GenericForeignKey.__get__(self, instance, cls)
231 if rel_obj is not None:
232 ct_match = ct_id == self.get_content_type(obj=rel_obj, using=instance._state.db).id
--> 233 pk_match = rel_obj._meta.pk.to_python(pk_val) == rel_obj.pk
234 if ct_match and pk_match:
235 return rel_obj
File /srv/www/testing/lib/.venv/lib/python3.10/site-packages/django/db/models/fields/__init__.py:1838, in IntegerField.to_python(self, value)
1836 return int(value)
1837 except (TypeError, ValueError):
-> 1838 raise exceptions.ValidationError(
1839 self.error_messages['invalid'],
1840 code='invalid',
1841 params={'value': value},
1842 )
ValidationError: ['“218-555-1212” value must be an integer.']
If step 3 (accessing case.content_object) is omitted, the problem does not occur because there is no cached content_object. Alternatively, if between 3 and 4 one does case.content_object = None to clear the cache, the problem does not occur.