#25505: Incomplete relation_tree for inherited proxied Models.
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Reporter: jelko | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.8
(models, ORM) | Keywords: models, meta, deletion,
Severity: Normal | relation, inheritance
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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`Options._populate_directed_relation_graph` produces an incomplete
`Options._relation_tree` for Models that have set `Meta.Proxy = True`.
Consider this setup:
BaseModel(models.Model) -> ProxyModel(BaseModel) [with Proxy = True] ->
ChildModel(ProxyModel)
In this case the OneToOne relation from ProxyModel to ChildModel is not
included in the proxymodel's `_meta._relation_tree`.
This is caused because `Options._populate_directed_relation_graph`
collects the relations by calling `model._meta._get_fields(reverse=False,
include_parents=False)`. Therefore the parent, in this case the ProxyModel
is not included.
This results in some unwanted situations. If you call `delete()` on a
ProxyModel, the BaseModel gets deleted, but the ChildModel instance stays
in the database and becomes orphaned.
Have a look at the attached models.py to replicate the setup. Compare the
behavior of `delete()` for instances of `ChipShop` and `IndianRestaurant`,
to see the problem.
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Ticket URL: <https://code.djangoproject.com/ticket/25505>
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