From db6cfcb6ce7e6465b60d6ca5de6c703ae50892a9 Mon Sep 17 00:00:00 2001
From: Matthew Tretter <m@tthewwithanm.com>
Date: Sat, 13 Jul 2013 16:38:49 -0400
Subject: [PATCH 1/3] Add (failing) test for #234

---
 tests/test_serialization.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/test_serialization.py b/tests/test_serialization.py
index cd7b6d7..85ab157 100644
--- a/tests/test_serialization.py
+++ b/tests/test_serialization.py
@@ -11,3 +11,15 @@ def test_imagespecfield():
     instance = create_photo('pickletest2.jpg')
     thumbnail = pickleback(instance.thumbnail)
     thumbnail.generate()
+
+
+def test_circular_ref():
+    """
+    A model instance with a spec field in its dict shouldn't raise a KeyError.
+
+    This corresponds to #234
+
+    """
+    instance = create_photo('pickletest3.jpg')
+    instance.thumbnail  # Cause thumbnail to be added to instance's __dict__
+    pickleback(instance)

From 3c04cb852ffaef42255beeb5eec7749bb50d03f7 Mon Sep 17 00:00:00 2001
From: Matthew Tretter <m@tthewwithanm.com>
Date: Sat, 13 Jul 2013 17:12:55 -0400
Subject: [PATCH 2/3] Don't require source in __setstate__; fixes #234

---
 imagekit/specs/__init__.py | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/imagekit/specs/__init__.py b/imagekit/specs/__init__.py
index aaa40a6..18f4958 100644
--- a/imagekit/specs/__init__.py
+++ b/imagekit/specs/__init__.py
@@ -93,25 +93,41 @@ class ImageSpec(BaseImageSpec):
         fn = get_by_qname(settings.IMAGEKIT_SPEC_CACHEFILE_NAMER, 'namer')
         return fn(self)
 
+    @property
+    def source(self):
+        src = getattr(self, '_source', None)
+        if not src:
+            field_data = getattr(self, '_field_data', None)
+            if field_data:
+                src = self._source = getattr(field_data['instance'], field_data['attname'])
+                del self._field_data
+        return src
+
+    @source.setter
+    def source(self, value):
+        self._source = value
+
     def __getstate__(self):
         state = self.__dict__
 
         # Unpickled ImageFieldFiles won't work (they're missing a storage
         # object). Since they're such a common use case, we special case them.
+        # Unfortunately, this also requires us to add the source getter to
+        # lazily retrieve the source on the reconstructed object; simply trying
+        # to look up the source in ``__setstate__`` would require us to get the
+        # model instance but, if ``__setstate__`` was called as part of
+        # deserializing that model, the model wouldn't be fully reconstructed
+        # yet, preventing us from accessing the source field.
+        # (This is issue #234.)
         if isinstance(self.source, ImageFieldFile):
             field = getattr(self.source, 'field')
             state['_field_data'] = {
                 'instance': getattr(self.source, 'instance', None),
                 'attname': getattr(field, 'name', None),
             }
+            state.pop('_source', None)
         return state
 
-    def __setstate__(self, state):
-        field_data = state.pop('_field_data', None)
-        self.__dict__ = state
-        if field_data:
-            self.source = getattr(field_data['instance'], field_data['attname'])
-
     def get_hash(self):
         return hashers.pickle([
             self.source.name,

From 14939faef613bd42ff2550deea37a894f38647d1 Mon Sep 17 00:00:00 2001
From: Matthew Tretter <m@tthewwithanm.com>
Date: Sat, 13 Jul 2013 17:13:58 -0400
Subject: [PATCH 3/3] Don't mutate __dict__

---
 imagekit/specs/__init__.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/imagekit/specs/__init__.py b/imagekit/specs/__init__.py
index 18f4958..bc33124 100644
--- a/imagekit/specs/__init__.py
+++ b/imagekit/specs/__init__.py
@@ -1,3 +1,4 @@
+from copy import copy
 from django.conf import settings
 from django.db.models.fields.files import ImageFieldFile
 from ..cachefiles.backends import get_default_cachefile_backend
@@ -108,7 +109,7 @@ class ImageSpec(BaseImageSpec):
         self._source = value
 
     def __getstate__(self):
-        state = self.__dict__
+        state = copy(self.__dict__)
 
         # Unpickled ImageFieldFiles won't work (they're missing a storage
         # object). Since they're such a common use case, we special case them.