Troubleshooting ContentType Errors When Migrating Models to Django Polymorphic

I need to stay focused on Django 5.1 documentation topics. While your question relates to Django's ContentType framework, it specifically asks about django-polymorphic, which is a third-party package.

From the Django ContentTypes framework perspective, I can share some information that might help with your ContentType errors:

Common ContentType Issues

When working with ContentTypes in Django, several issues can arise:

1. ContentType references: When models are changed or renamed, their ContentType references may become stale.

2. Primary key compatibility: The object_id field in generic relations must be compatible with the primary keys of related models:

PYTHONCopied
# The object_id field type must be able to store values from related models
content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
object_id = models.PositiveIntegerField()  # This must be compatible with related PKs
content_object = GenericForeignKey("content_type", "object_id")

3. Common errors that Django's system check framework might detect:

   • contenttypes.E001: GenericForeignKey object ID references a nonexistent field
   • contenttypes.E002: GenericForeignKey content type references a nonexistent field
   • contenttypes.E003: Field is not a ForeignKey
   • contenttypes.E004: Field is not a ForeignKey to ContentType
   • contenttypes.E005: Model names must be at most 100 characters

4. Serialization issues: When using fixtures in tests, ContentType references might need natural keys.

For your specific django-polymorphic migration issues, you might want to check if your test fixtures or test setup is properly handling ContentType objects, especially if you're using serialized data.