GH-341: Warning if HistoricalRecords(inherit=False) in an abstract class (#472)

* First commit for issue #341 - Warning if inerhit is set to False in an abstract class

* First commit for issue #341 - Warning if inerhit is set to False in an abstract class

* Fixed flake8 errors and tested that warning is raised

* Added changes.rst

* Updated warning with tests to improve coverage

Author: Ross Mechanic

CHANGES.rst

@@ -5,6 +5,7 @@ Unreleased
 ----------
 - Add `custom_model_name` parameter to the constructor of `HistoricalRecords` (gh-451)
 - Fix header on history pages when custom site_header is used (gh-448)
+- Raise warning if HistoricalRecords(inherit=False) is in an abstract model (gh-341)
 
 2.5.1 (2018-10-19)
 ------------------

simple_history/models.py

@@ -4,6 +4,7 @@
 import importlib
 import threading
 import uuid
+import warnings
 
 from django.apps import apps
 from django.conf import settings
@@ -21,8 +22,8 @@
 from . import exceptions
 from .manager import HistoryDescriptor
 from .signals import (
-    pre_create_historical_record,
     post_create_historical_record,
+    pre_create_historical_record
 )
 
 registered_models = {}
@@ -71,6 +72,11 @@ def contribute_to_class(self, cls, name):
         models.signals.class_prepared.connect(self.finalize, weak=False)
         self.add_extra_methods(cls)
 
+        if cls._meta.abstract and not self.inherit:
+            msg = "HistoricalRecords added to abstract model ({}) without " \
+                  "inherit=True".format(self.cls.__name__)
+            warnings.warn(msg, UserWarning)
+
     def add_extra_methods(self, cls):
         def save_without_historical_record(self, *args, **kwargs):
             """

simple_history/tests/tests/test_models.py

@@ -1048,3 +1048,22 @@ def test_changed_value_lost(self):
         historical = self.get_first_historical()
         instance = historical.instance
         self.assertEqual(instance.place, new_place)
+
+
+class WarningOnAbstractModelWithInheritFalseTest(TestCase):
+    def test_warning_on_abstract_model_with_inherit_false(self):
+
+        with warnings.catch_warnings(record=True) as w:
+            class AbstractModelWithInheritFalse(models.Model):
+                string = models.CharField()
+                history = HistoricalRecords()
+
+                class Meta:
+                    abstract = True
+
+            self.assertEqual(len(w), 1)
+            self.assertTrue(issubclass(w[0].category, UserWarning))
+            self.assertEqual(str(w[0].message),
+                             'HistoricalRecords added to abstract model '
+                             '(AbstractModelWithInheritFalse) without '
+                             'inherit=True')