From 500dd470cdbfcf9be827f0eaca2dacb7b82b4014 Mon Sep 17 00:00:00 2001
From: Keryn Knight <keryn@kerynknight.com>
Date: Tue, 1 Jul 2014 14:36:22 +0100
Subject: [PATCH 1/2] Tests demonstrating how lying about a `modified` field
 ought to be possible.

---
 model_utils/tests/tests.py | 64 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/model_utils/tests/tests.py b/model_utils/tests/tests.py
index 9de6892..90cc661 100644
--- a/model_utils/tests/tests.py
+++ b/model_utils/tests/tests.py
@@ -1051,6 +1051,70 @@ class TimeStampedModelTests(TestCase):
         t1.save()
         self.assertTrue(t2.modified < t1.modified)
 
+    def test_overriding_created_via_object_creation(self):
+        """
+        Setting the created date when first creating an object
+        should be permissable.
+        """
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1 = TimeStamp.objects.create(created=different_date)
+        self.assertEqual(t1.created, different_date)
+        self.assertNotEqual(t1.modified, different_date)
+
+
+    def test_overriding_modified_via_object_creation(self):
+        """
+        Setting the modified date explicitly should be possible when
+        first creating an object, but not thereafter.
+        """
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1 = TimeStamp.objects.create(modified=different_date)
+        self.assertEqual(t1.modified, different_date)
+        self.assertNotEqual(t1.created, different_date)
+
+    def test_overriding_created_after_object_created(self):
+        """
+        The created date may be changed post-create
+        """
+        t1 = TimeStamp.objects.create()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.created = different_date
+        t1.save()
+        self.assertEqual(t1.created, different_date)
+
+    def test_overriding_modified_after_object_created(self):
+        """
+        The modified date should always be updated when the object
+        is saved, regardless of attempts to change it.
+        """
+        t1 = TimeStamp.objects.create()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.modified = different_date
+        t1.save()
+        self.assertNotEqual(t1.modified, different_date)
+
+    def test_overrides_using_save(self):
+        """
+        The first time an object is saved, allow modification of both
+        created and modified fields.
+        After that, only created may be modified manually.
+        """
+        t1 = TimeStamp()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.created = different_date
+        t1.modified = different_date
+        t1.save()
+        self.assertEqual(t1.created, different_date)
+        self.assertEqual(t1.modified, different_date)
+        different_date2 = datetime.today() - timedelta(weeks=26)
+        t1.created = different_date2
+        t1.modified = different_date2
+        t1.save()
+        self.assertEqual(t1.created, different_date2)
+        self.assertNotEqual(t1.modified, different_date2)
+        self.assertNotEqual(t1.modified, different_date)
+
+
 
 
 class TimeFramedModelTests(TestCase):

From e353a01a9a74bc624724e6e507b47e7697afe910 Mon Sep 17 00:00:00 2001
From: Keryn Knight <keryn@kerynknight.com>
Date: Tue, 1 Jul 2014 14:37:41 +0100
Subject: [PATCH 2/2] Implemented ability to change modified fields manually.

---
 model_utils/fields.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/model_utils/fields.py b/model_utils/fields.py
index 8728d56..7fe1c83 100644
--- a/model_utils/fields.py
+++ b/model_utils/fields.py
@@ -30,8 +30,14 @@ class AutoLastModifiedField(AutoCreatedField):
 
     """
     def pre_save(self, model_instance, add):
-        value = now()
-        setattr(model_instance, self.attname, value)
+        if add and hasattr(model_instance, self.attname):
+            # when creating an instance and the modified date is set
+            # don't change the value, assume the developer wants that
+            # control.
+            value = getattr(model_instance, self.attname)
+        else:
+            value = now()
+            setattr(model_instance, self.attname, value)
         return value