Fixes #20587: Handle stale ContentTypes in has_feature() #20592
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When deleting stale ContentTypes during remove_stale_contenttypes, the pre_delete signal triggers notify_object_changed(), which calls has_feature() with the ContentType instance. For stale types (those with no corresponding model class), model_class() returns None, which then gets passed to issubclass() in the feature test lambda, causing a TypeError. The previous implementation in has_feature() checked for None before attempting ObjectType lookup. The optimization in 5ceb6a6 removed this safety check when refactoring the ContentType code path to use direct feature registry lookups. This restores the null check to maintain the original behavior of returning False for stale ContentTypes.
jnovinger
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jeremystretch
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Oct 15, 2025
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Fixes: #20587
Fixes #20587 (and its duplicate #20588) by adding a null check when handling stale
ContentTypes inhas_feature().When running
remove_stale_contenttypes(executed byupgrade.sh), the management command fails withTypeError: issubclass() arg 1 must be a class. This occurs when deleting ContentTypes that no longer have corresponding model classes—referred to as "stale" ContentTypes. These arise when models are renamed/removed between versions or when plugins are uninstalled.The error path:
pre_deletesignal fires when deleting the stale ContentTypenotify_object_changed()signal handler callshas_feature(instance, 'notifications')has_feature()callsmodel_class()on the ContentType, which returnsNonefor stale typesNonegets passed directly to the feature test lambda:issubclass(None, NotificationsMixin)→ TypeErrorRoot Cause:
Commit 5ceb6a6 (which fixed #20290) changed the ContentType code path in
has_feature()to use direct feature registry lookups in addition to ObjectType lookups. However, this refactoring inadvertently removed the null safety check that existed in the previous implementation.https://gist.github.com/jnovinger/35948fc653c0425a5f9b207f9b77883f is available as a reproduction script to verify this fix.