Add feature to allow historical records to be deleted when master is deleted

Author: rwlogel

CHANGES.rst

@@ -1,6 +1,10 @@
 Changes
 =======
 
+Unreleased
+----------
+- Add ability to cascade delete historical records when master record is deleted 
+
 2.4.0 (2018-09-20)
 ------------------
 - Add pre and post create_historical_record signals (gh-426)

docs/advanced.rst

@@ -424,6 +424,19 @@ If you want to save a model without a historical record, you can use the followi
     poll = Poll(question='something')
     poll.save_without_historical_record()
 
+Deleting historical record
+--------------------------
+
+In some circumstances you may want to delete all the historical records when the master record is deleted.  This can
+be accomplished by setting ``cascade_delete_history=True``.
+
+.. code-block:: python
+
+    class Poll(models.Model):
+        question = models.CharField(max_length=200)
+        history = HistoricalRecords(cascade_delete_history=True)
+
+
 History Diffing
 -------------------
 
@@ -465,4 +478,4 @@ django-simple-history includes signals that helps you provide custom behaviour w
 
     @receiver(pre_create_historical_record)
         def post_create_historical_record(sender, instance, history_instance, **kwargs):
-            print("Sent after saving historical record")
+            print("Sent after saving historical record")

simple_history/models.py

@@ -44,7 +44,8 @@ def __init__(self, verbose_name=None, bases=(models.Model,),
                  user_related_name='+', table_name=None, inherit=False,
                  excluded_fields=None, history_id_field=None,
                  history_change_reason_field=None,
-                 user_model=None, get_user=default_get_user):
+                 user_model=None, get_user=default_get_user,
+                 cascade_delete_history=False):
         self.user_set_verbose_name = verbose_name
         self.user_related_name = user_related_name
         self.table_name = table_name
@@ -53,6 +54,7 @@ def __init__(self, verbose_name=None, bases=(models.Model,),
         self.history_change_reason_field = history_change_reason_field
         self.user_model = user_model
         self.get_user = get_user
+        self.cascade_delete_history = cascade_delete_history
         if excluded_fields is None:
             excluded_fields = []
         self.excluded_fields = excluded_fields
@@ -340,7 +342,11 @@ def post_save(self, instance, created, **kwargs):
             self.create_historical_record(instance, created and '+' or '~')
 
     def post_delete(self, instance, **kwargs):
-        self.create_historical_record(instance, '-')
+        if self.cascade_delete_history:
+            manager = getattr(instance, self.manager_name)
+            manager.all().delete()
+        else:
+            self.create_historical_record(instance, '-')
 
     def create_historical_record(self, instance, history_type):
         history_date = getattr(instance, '_history_date', now())

simple_history/tests/models.py

@@ -61,7 +61,7 @@ class WaterLevel(models.Model):
     level = models.IntegerField()
     date = models.DateTimeField()
 
-    history = HistoricalRecords()
+    history = HistoricalRecords(cascade_delete_history=True)
 
     @property
     def _history_date(self):

simple_history/tests/tests/test_models.py

@@ -170,6 +170,20 @@ def test_delete_verify_change_reason_explicity(self):
             'history_type': "-"
         })
 
+    def test_cascade_delete_history(self):
+        thames = WaterLevel.objects.create(waters="Thames", level=2.5,
+                                           date=today)
+        nile = WaterLevel.objects.create(waters="Nile", level=2.5,
+                                         date=today)
+
+        self.assertEqual(len(thames.history.all()), 1)
+        self.assertEqual(len(nile.history.all()), 1)
+
+        nile.delete()
+
+        self.assertEqual(len(thames.history.all()), 1)
+        self.assertEqual(len(nile.history.all()), 0)
+
     def test_save_without_historical_record(self):
         pizza_place = Restaurant.objects.create(name='Pizza Place', rating=3)
         pizza_place.rating = 4