From 13919f55ffaba343706d70d0e60d92e2d451df39 Mon Sep 17 00:00:00 2001
From: Aarni Koskela <akx@iki.fi>
Date: Mon, 27 Jun 2016 08:56:07 +0300
Subject: [PATCH] Restore cast-on-assign behavior on Django 1.8+

Turns out the future-deprecated SubfieldBase class did more
than what was initially thought.  Since it is removed in
Django 1.10+, for clarity we no longer use it at all.
Instead we intern the behavior of its `Creator` descriptor
class as `CastOnAssignDescriptor`.

Test cases and original bug report by @andrewdodd. Thanks!

Fixes #60
Refs https://code.djangoproject.com/ticket/26807
Refs 826005087541805620be3daffab3e8d106eedc2f
---
 enumfields/fields.py   | 26 ++++++++++++++++++++++++--
 tests/test_issue_60.py | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_issue_60.py

diff --git a/enumfields/fields.py b/enumfields/fields.py
index bdb9988..e3c0d49 100644
--- a/enumfields/fields.py
+++ b/enumfields/fields.py
@@ -10,10 +10,28 @@
 from .compat import import_string
 from .forms import EnumChoiceField
 
-metaclass = models.SubfieldBase if django.VERSION < (1, 8) else type
 
+class CastOnAssignDescriptor(object):
+    """
+    A property descriptor which ensures that `field.to_python()` is called on _every_ assignment to the field.
 
-class EnumFieldMixin(six.with_metaclass(metaclass)):
+    This used to be provided by the `django.db.models.subclassing.Creator` class, which in turn
+    was used by the deprecated-in-Django-1.10 `SubfieldBase` class, hence the reimplementation here.
+    """
+
+    def __init__(self, field):
+        self.field = field
+
+    def __get__(self, obj, type=None):
+        if obj is None:
+            return self
+        return obj.__dict__[self.field.name]
+
+    def __set__(self, obj, value):
+        obj.__dict__[self.field.name] = self.field.to_python(value)
+
+
+class EnumFieldMixin(object):
     def __init__(self, enum, **options):
         if isinstance(enum, six.string_types):
             self.enum = import_string(enum)
@@ -25,6 +43,10 @@ def __init__(self, enum, **options):
 
         super(EnumFieldMixin, self).__init__(**options)
 
+    def contribute_to_class(self, cls, name):
+        super(EnumFieldMixin, self).contribute_to_class(cls, name)
+        setattr(cls, name, CastOnAssignDescriptor(self))
+
     def to_python(self, value):
         if value is None or value == '':
             return None
diff --git a/tests/test_issue_60.py b/tests/test_issue_60.py
new file mode 100644
index 0000000..576bf73
--- /dev/null
+++ b/tests/test_issue_60.py
@@ -0,0 +1,34 @@
+import pytest
+
+from .models import MyModel
+
+try:
+    from .enums import Color  # Use the new location of Color enum
+except ImportError:
+    Color = MyModel.Color  # Attempt the 0.7.4 location of color enum
+
+
+@pytest.mark.django_db
+def test_fields_value_is_enum_when_unsaved():
+    obj = MyModel(color='r')
+    assert Color.RED == obj.color
+
+
+@pytest.mark.django_db
+def test_fields_value_is_enum_when_saved():
+    obj = MyModel(color='r')
+    obj.save()
+    assert Color.RED == obj.color
+
+
+@pytest.mark.django_db
+def test_fields_value_is_enum_when_created():
+    obj = MyModel.objects.create(color='r')
+    assert Color.RED == obj.color
+
+
+@pytest.mark.django_db
+def test_fields_value_is_enum_when_retrieved():
+    MyModel.objects.create(color='r')
+    obj = MyModel.objects.all()[:1][0]  # .first() not available on all Djangoes
+    assert Color.RED == obj.color