Merge pull request #242 from romgar/ticket_241_double_monitor_field_recursion_error

Tests to demonstrate recursion error with double MonitorField and defer()/only() usage

model_utils/fields.py

@@ -110,6 +110,9 @@ class MonitorField(models.DateTimeField):
         return getattr(instance, self.monitor)
 
     def _save_initial(self, sender, instance, **kwargs):
+        if django.VERSION >= (1, 10) and self.monitor in instance.get_deferred_fields():
+            # Fix related to issue #241 to avoid recursive error on double monitor fields
+            return
         setattr(instance, self.monitor_attname,
                 self.get_monitored_value(instance))
 

model_utils/tests/models.py

@@ -105,6 +105,12 @@ class MonitorWhenEmpty(models.Model):
     name_changed = MonitorField(monitor="name", when=[])
 
 
+class DoubleMonitored(models.Model):
+    name = models.CharField(max_length=25)
+    name_changed = MonitorField(monitor="name")
+    name2 = models.CharField(max_length=25)
+    name_changed2 = MonitorField(monitor="name2")
+
 
 class Status(StatusModel):
     STATUS = Choices(

model_utils/tests/tests.py

@@ -2,6 +2,8 @@ from __future__ import unicode_literals
 
 from datetime import datetime, timedelta
 
+from freezegun import freeze_time
+
 try:
     from unittest import skipUnless
 except ImportError: # Python 2.6
@@ -33,7 +35,7 @@ from model_utils.tests.models import (
     Tracked, TrackedFK, InheritedTrackedFK, TrackedNotDefault, TrackedNonFieldAttr, TrackedMultiple,
     InheritedTracked, TrackedFileField, StatusFieldDefaultFilled, StatusFieldDefaultNotFilled,
     InheritanceManagerTestChild3, StatusFieldChoicesName,
-    SoftDeletable)
+    SoftDeletable, DoubleMonitored)
 
 
 class MigrationsTests(TestCase):
@@ -255,6 +257,26 @@ class MonitorWhenEmptyFieldTests(TestCase):
         self.assertEqual(self.instance.name_changed, self.created)
 
 
+class MonitorDoubleFieldTests(TestCase):
+
+    def setUp(self):
+        DoubleMonitored.objects.create(name='Charlie', name2='Charlie2')
+
+    def test_recursion_error_with_only(self):
+        # Any field passed to only() is generating a recursion error
+        list(DoubleMonitored.objects.only('id'))
+
+    def test_recursion_error_with_defer(self):
+        # Only monitored fields passed to defer() are failing
+        list(DoubleMonitored.objects.defer('name'))
+
+    def test_monitor_still_works_with_deferred_fields_filtered_out_of_save_initial(self):
+        obj = DoubleMonitored.objects.defer('name').get(name='Charlie')
+        with freeze_time("2016-12-01"):
+            obj.name = 'Charlie2'
+            obj.save()
+        self.assertEqual(obj.name_changed, datetime(2016, 12, 1))
+
 
 class StatusFieldTests(TestCase):