Allow AuditlogHistoryField to block cascading deletes

src/auditlog/models.py

@@ -7,7 +7,7 @@
 from django.contrib.contenttypes.fields import GenericRelation
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import FieldDoesNotExist
-from django.db import models
+from django.db import models, DEFAULT_DB_ALIAS
 from django.db.models import QuerySet, Q
 from django.utils import formats, timezone
 from django.utils.encoding import python_2_unicode_compatible, smart_text
@@ -321,9 +321,13 @@ class AuditlogHistoryField(GenericRelation):
 
  :param pk_indexable: Whether the primary key for this model is not an :py:class:`int` or :py:class:`long`.
  :type pk_indexable: bool
+ :param delete_related: By default, including a generic relation into a model will cause all related objects to be
+ cascade-deleted when the parent object is deleted. Passing False to this overrides this behavior, retaining
+ the full auditlog history for the object. Defaults to True, because that's Django's default behavior.
+ :type delete_related: bool
  """
 
- def __init__(self, pk_indexable=True, **kwargs):
+ def __init__(self, pk_indexable=True, delete_related=True, **kwargs):
  kwargs['to'] = LogEntry
 
  if pk_indexable:
@@ -332,8 +336,22 @@ def __init__(self, pk_indexable=True, **kwargs):
  kwargs['object_id_field'] = 'object_pk'
 
  kwargs['content_type_field'] = 'content_type'
+ self.delete_related = delete_related
  super(AuditlogHistoryField, self).__init__(**kwargs)
 
+ def bulk_related_objects(self, objs, using=DEFAULT_DB_ALIAS):
+ """
+ Return all objects related to ``objs`` via this ``GenericRelation``.
+ """
+ if self.delete_related:
+ return super(AuditlogHistoryField, self).bulk_related_objects(objs, using)
+
+ # When deleting, Collector.collect() finds related objects using this
+ # method. However, because we don't want to delete these related
+ # objects, we simply return an empty list.
+ return []
+
+
 # South compatibility for AuditlogHistoryField
 try:
  from south.modelsinspector import add_introspection_rules

src/auditlog_tests/models.py

@@ -209,6 +209,12 @@ class PostgresArrayFieldModel(models.Model):
  history = AuditlogHistoryField()
 
 
+class NoDeleteHistoryModel(models.Model):
+ integer = models.IntegerField(blank=True, null=True)
+
+ history = AuditlogHistoryField(delete_related=False)
+
+
 auditlog.register(AltPrimaryKeyModel)
 auditlog.register(UUIDPrimaryKeyModel)
 auditlog.register(ProxyModel)
@@ -222,3 +228,4 @@ class PostgresArrayFieldModel(models.Model):
 auditlog.register(ChoicesFieldModel)
 auditlog.register(CharfieldTextfieldModel)
 auditlog.register(PostgresArrayFieldModel)
+auditlog.register(NoDeleteHistoryModel)

src/auditlog_tests/tests.py

@@ -16,7 +16,7 @@
 from auditlog_tests.models import SimpleModel, AltPrimaryKeyModel, UUIDPrimaryKeyModel, \
  ProxyModel, SimpleIncludeModel, SimpleExcludeModel, SimpleMappingModel, RelatedModel, \
  ManyRelatedModel, AdditionalDataIncludedModel, DateTimeFieldModel, ChoicesFieldModel, \
- CharfieldTextfieldModel, PostgresArrayFieldModel
+ CharfieldTextfieldModel, PostgresArrayFieldModel, NoDeleteHistoryModel
 from auditlog import compat
 
 
@@ -663,3 +663,33 @@ def test_auditlog_admin(self):
  res = self.client.get("/admin/auditlog/logentry/{}/history/".format(log_pk))
  assert res.status_code == 200
 
+
+class NoDeleteHistoryTest(TestCase):
+ def test_delete_related(self):
+ instance = SimpleModel.objects.create(integer=1)
+ assert LogEntry.objects.all().count() == 1
+ instance.integer = 2
+ instance.save()
+ assert LogEntry.objects.all().count() == 2
+
+ instance.delete()
+ entries = LogEntry.objects.order_by('id')
+
+ # The "DELETE" record is always retained
+ assert LogEntry.objects.all().count() == 1
+ assert entries.first().action == LogEntry.Action.DELETE
+
+ def test_no_delete_related(self):
+ instance = NoDeleteHistoryModel.objects.create(integer=1)
+ self.assertEqual(LogEntry.objects.all().count(), 1)
+ instance.integer = 2
+ instance.save()
+ self.assertEqual(LogEntry.objects.all().count(), 2)
+
+ instance.delete()
+ entries = LogEntry.objects.order_by('id')
+ self.assertEqual(entries.count(), 3)
+ self.assertEqual(
+ list(entries.values_list('action', flat=True)),
+ [LogEntry.Action.CREATE, LogEntry.Action.UPDATE, LogEntry.Action.DELETE]
+ )