InheritanceManager queries always return an instance of InheritanceQuerySet

[ahmadkkhaled]

Problem

I am using a custom model manager that extends InheritanceManager like so:

class Manager(InheritanceManager):
   def custom_method(self):
         return self.filter(...)

because the return type of get_queryset() of InheritanceManagerMixin is hardcoded to return self._queryset_class(self.model) it's impossible for me to chain the methods of my custom Manager:

Model.objects.all().custom_method() will fail since .all() will return an instance of InheritanceQuerySet and my custom_method isn't defined there, it's rather defined on Manager.

Although this slight confusion is mentioned in the documentation here it's still not clear for the user how to properly extend InheritanceManager with custom managers

Environment

• Django Model Utils version: 4.1.1
• Django version: 3.2.11
• Python version: 3.8

Code examples

Model.objects.custom_method() works
Model.objects.filter().custom_method() fails with exception 'InheritanceQuerySet' object has no attribute 'custom_method'

[ahmadkkhaled]

related #205

[ahmadkkhaled]

I managed to workaround this by extending InheritanceQuerySet like so:

CustomQuerySet(InheritanceQuerySet):
   def custom_function(self):
       ...

then using my CustomQuerySet in the model like so:

Model(models.Model):
   objects = CustomQuerySet.as_manager()

This way I retain djano-model-util InheritanceManager functionality and allow for chaining custom methods defined on the queryset, I still think this should be made more clear for the user in the documentation, because directly inheriting from InheritanceManager seems to cause problems