Change FieldTracker current for unsaved model

Return None values instead of an empty dict

model_utils/tests/tests.py

@@ -691,15 +691,6 @@ def test_pre_save_has_changed(self):
         self.instance.name = 'new age'
         self.assertHasChanged(name=True, number=True)
 
-    def test_pre_save_changed(self):
-        self.assertChanged()
-        self.instance.name = 'new age'
-        self.assertChanged()
-        self.instance.number = 8
-        self.assertChanged()
-        self.instance.name = ''
-        self.assertChanged()
-
     def test_pre_save_previous(self):
         self.assertPrevious(name=None, number=None)
         self.instance.name = 'new age'
@@ -718,24 +709,33 @@ def setUp(self):
     def test_descriptor(self):
         self.assertTrue(isinstance(self.tracked_class.tracker, FieldTracker))
 
+    def test_pre_save_changed(self):
+        self.assertChanged(name=None, number=None, id=None)
+        self.instance.name = 'new age'
+        self.assertChanged(name=None, number=None, id=None)
+        self.instance.number = 8
+        self.assertChanged(name=None, number=None, id=None)
+        self.instance.name = ''
+        self.assertChanged(name=None, number=None, id=None)
+
     def test_first_save(self):
         self.assertHasChanged(name=True, number=True)
         self.assertPrevious(name=None, number=None)
         self.assertCurrent(name='', number=None, id=None)
-        self.assertChanged()
+        self.assertChanged(name=None, number=None, id=None)
         self.instance.name = 'retro'
         self.instance.number = 4
         self.assertHasChanged(name=True, number=True)
         self.assertPrevious(name=None, number=None)
         self.assertCurrent(name='retro', number=4, id=None)
-        self.assertChanged()
+        self.assertChanged(name=None, number=None, id=None)
         # Django 1.4 doesn't have update_fields
         if django.VERSION >= (1, 5, 0):
             self.instance.save(update_fields=[])
             self.assertHasChanged(name=True, number=True)
             self.assertPrevious(name=None, number=None)
             self.assertCurrent(name='retro', number=4, id=None)
-            self.assertChanged()
+            self.assertChanged(name=None, number=None, id=None)
             self.assertRaises(ValueError, self.instance.save,
                     update_fields=['number'])
 
@@ -804,6 +804,15 @@ def setUp(self):
         self.instance = self.tracked_class()
         self.tracker = self.instance.name_tracker
 
+    def test_pre_save_changed(self):
+        self.assertChanged(name=None)
+        self.instance.name = 'new age'
+        self.assertChanged(name=None)
+        self.instance.number = 8
+        self.assertChanged(name=None)
+        self.instance.name = ''
+        self.assertChanged(name=None)
+
     def test_post_save_has_changed(self):
         self.update_instance(name='retro', number=4)
         self.assertHasChanged(name=False, number=None)
@@ -855,9 +864,20 @@ def test_pre_save_has_changed(self):
             super(FieldTrackedModelMultiTests, self).test_pre_save_has_changed()
 
     def test_pre_save_changed(self):
-        for tracker in self.trackers:
-            self.tracker = tracker
-            super(FieldTrackedModelMultiTests, self).test_pre_save_changed()
+        self.tracker = self.instance.name_tracker
+        self.assertChanged(name=None)
+        self.instance.name = 'new age'
+        self.assertChanged(name=None)
+        self.instance.number = 8
+        self.assertChanged(name=None)
+        self.instance.name = ''
+        self.assertChanged(name=None)
+        self.tracker = self.instance.number_tracker
+        self.assertChanged(number=None)
+        self.instance.name = 'new age'
+        self.assertChanged(number=None)
+        self.instance.number = 8
+        self.assertChanged(number=None)
 
     def test_pre_save_previous(self):
         for tracker in self.trackers:
@@ -961,16 +981,71 @@ class ModelTrackerTests(FieldTrackerTests):
 
     tracked_class = ModelTracked
 
+    def test_pre_save_changed(self):
+        self.assertChanged()
+        self.instance.name = 'new age'
+        self.assertChanged()
+        self.instance.number = 8
+        self.assertChanged()
+        self.instance.name = ''
+        self.assertChanged()
+
+    def test_first_save(self):
+        self.assertHasChanged(name=True, number=True)
+        self.assertPrevious(name=None, number=None)
+        self.assertCurrent(name='', number=None, id=None)
+        self.assertChanged()
+        self.instance.name = 'retro'
+        self.instance.number = 4
+        self.assertHasChanged(name=True, number=True)
+        self.assertPrevious(name=None, number=None)
+        self.assertCurrent(name='retro', number=4, id=None)
+        self.assertChanged()
+        # Django 1.4 doesn't have update_fields
+        if django.VERSION >= (1, 5, 0):
+            self.instance.save(update_fields=[])
+            self.assertHasChanged(name=True, number=True)
+            self.assertPrevious(name=None, number=None)
+            self.assertCurrent(name='retro', number=4, id=None)
+            self.assertChanged()
+            self.assertRaises(ValueError, self.instance.save,
+                    update_fields=['number'])
+
 
 class ModelTrackedModelCustomTests(FieldTrackedModelCustomTests):
 
     tracked_class = ModelTrackedNotDefault
 
+    def test_pre_save_changed(self):
+        self.assertChanged()
+        self.instance.name = 'new age'
+        self.assertChanged()
+        self.instance.number = 8
+        self.assertChanged()
+        self.instance.name = ''
+        self.assertChanged()
+
 
 class ModelTrackedModelMultiTests(FieldTrackedModelMultiTests):
 
     tracked_class = ModelTrackedMultiple
 
+    def test_pre_save_changed(self):
+        self.tracker = self.instance.name_tracker
+        self.assertChanged()
+        self.instance.name = 'new age'
+        self.assertChanged()
+        self.instance.number = 8
+        self.assertChanged()
+        self.instance.name = ''
+        self.assertChanged()
+        self.tracker = self.instance.number_tracker
+        self.assertChanged()
+        self.instance.name = 'new age'
+        self.assertChanged()
+        self.instance.number = 8
+        self.assertChanged()
+
 
 class ModelTrackerForeignKeyTests(FieldTrackerForeignKeyTests):
 

model_utils/tracker.py

@@ -30,7 +30,7 @@ def has_changed(self, field):
         if not self.instance.pk:
             return True
         elif field in self.saved_data:
-            return self.saved_data.get(field) != self.get_field(field)
+            return self.previous(field) != self.get_field_value(field)
         else:
             raise FieldError('field "%s" not tracked' % field)
 
@@ -40,11 +40,11 @@ def previous(self, field):
 
     def changed(self):
         """Returns dict of fields that changed since save (with old values)"""
-        if not self.instance.pk:
-            return {}
-        saved = self.saved_data.items()
-        current = self.current()
-        return dict((k, v) for k, v in saved if v != current[k])
+        return dict(
+            (field, self.previous(field))
+            for field in self.fields
+            if self.has_changed(field)
+        )
 
 
 class FieldTracker(object):
@@ -97,7 +97,14 @@ def __get__(self, instance, owner):
 
 
 class ModelInstanceTracker(FieldInstanceTracker):
-    pass
+
+    def changed(self):
+        """Returns dict of fields that changed since save (with old values)"""
+        if not self.instance.pk:
+            return {}
+        saved = self.saved_data.items()
+        current = self.current()
+        return dict((k, v) for k, v in saved if v != current[k])
 
 
 class ModelTracker(FieldTracker):