Model inheritance doesn't work as expected in certain cases

[oamg]

Model inheritance doesn't work as expected in certain cases

[fernflower]

Looks like the key issue is items list being shared between the 2 models. Did some debugging in redhatsignedrpmsscanner actor and every time an rpm is added to one model's items list it immediately appears in the second model's list.

(Pdb) signed_pkgs.items,unsigned_pkgs.items
([], [])
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(38)process()
-> continue
(Pdb) signed_pkgs.items,unsigned_pkgs.items
([<leapp.models.installedrpm.RPM object at 0x7fa5d76b0890>], [<leapp.models.installedrpm.RPM object at 0x7fa5d76b0890>])
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(32)process()
-> for pkg in rpm_pkgs.items:
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(34)process()
-> if any(key in pkg.pgpsig for key in RH_SIGS) or \
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(35)process()
-> (pkg.name == 'gpg-pubkey' and pkg.packager.startswith('Red Hat, Inc.')):
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(40)process()
-> unsigned_pkgs.items.append(pkg)
(Pdb) n
> /home/ivasilev/projects/leapp-repository/repos/system_upgrade/el7toel8/actors/redhatsignedrpmscanner/actor.py(32)process()
-> for pkg in rpm_pkgs.items:
(Pdb) signed_pkgs.items,unsigned_pkgs.items
([<leapp.models.installedrpm.RPM object at 0x7fa5d76b0890>, <leapp.models.installedrpm.RPM object at 0x7fa5d76b08d0>], [<leapp.models.installedrpm.RPM object at 0x7fa5d76b0890>, <leapp.models.installedrpm.RPM object at 0x7fa5d76b08d0>])
(Pdb) signed_pkgs.items == unsigned_pkgs.items
True

[fernflower]

I suspect that base class fields are not copied correctly in ModelMeta.__new__ -> this causes base class and child class to share reference to the same object unless the field has been specifically redefined in child class

leapp/models/__init__.py:ModelMeta:__new__

kls_attrs = (getattr(klass, 'fields', None) or {}).copy()

iiuc this won't create proper copy of List field changing a reference to the actual underlying list object.
Created a leapp PR with bug localization\eye bleeding fix oamg/leapp#513

[bocekm]

@fernflower, isn't this fixed by oamg/leapp#513?

[fernflower]

@bocekm it is, thank you!