Prevents ModelState instance from being shared by model and clone

django_cloneable/models.py

@@ -14,7 +14,9 @@ def _clone_copy(self):
         import copy
         if not self.instance.pk:
             raise ValueError('Instance must be saved before it can be cloned.')
-        return copy.copy(self.instance)
+        duplicate = copy.copy(self.instance)
+        duplicate._state = models.base.ModelState()
+        return duplicate
 
     def _clone_prepare(self, duplicate, exclude=None):
         # Setting pk to None tricks Django into not trying to overwrite the old

tests/models.py

@@ -9,7 +9,12 @@ class ModelWithFields(CloneableMixin, models.Model):
     integer = models.IntegerField(default=0)
     date = models.DateField(default=date(2000, 1, 1))
 
-
 class ModelWithCustomPK(CloneableMixin, models.Model):
     key = models.CharField(max_length=50, primary_key=True)
     value = models.IntegerField()
+
+class RelatedModel(models.Model):
+	pass
+
+class ModelWithFK(CloneableMixin, models.Model):
+	related = models.ForeignKey(RelatedModel, related_name='+', null=True, on_delete=models.SET_NULL)

tests/test_cloneable.py

@@ -3,6 +3,8 @@
 
 from .models import ModelWithCustomPK
 from .models import ModelWithFields
+from .models import RelatedModel
+from .models import ModelWithFK
 
 
 class CloneableTests(TestCase):
@@ -27,3 +29,13 @@ def test_must_provide_new_pk_if_its_custom_field(self):
         assert i2.pk == 'bar'
         assert i1.pk != i2.pk
         assert i2.value == 42
+
+    def test_cloning_object_allows_overwriting_fk_reference(self):
+        i1 = ModelWithFK.objects.create()
+        i1.related = RelatedModel.objects.create()
+        i1.save()
+
+        i2 = i1.clone()
+        i2.related = RelatedModel.objects.create()
+        i2.save()
+        assert i1.related != i2.related