ImageSpecFile is a proper File

Previously, ImageSpecFile was a file-like object, but didn't actually
extend any of the file classes. Because of this, some of Django's file-
handling code was duplicated. More importantly, instances didn't always
behave as one might expect (if one were familiar with ImageFields),
particularly when the source image was empty. This could have been
especially confusing in templates. (For example, because
ImageSpecFields whose source images didn't exist were still truthy.)

imagekit/management/commands/ikflush.py

@@ -27,7 +27,7 @@ def flush_cache(apps, options):
                 for obj in model.objects.order_by('-id'):
                     for spec_file in get_spec_files(obj):
                         if spec_file is not None:
-                            spec_file._delete()
+                            spec_file.delete(save=False)
                         if spec_file.field.pre_cache:
                             spec_file._create()
     else:

imagekit/models.py

@@ -137,15 +137,28 @@ class _ImageSpecFileMixin(object):
         return img, content
 
 
-class ImageSpecFile(_ImageSpecFileMixin):
+class ImageSpecFile(_ImageSpecFileMixin, ImageFieldFile):
     def __init__(self, instance, field, attname, source_file):
-        self.field = field
-        self._img = None
-        self._file = None
-        self.instance = instance
+        ImageFieldFile.__init__(self, instance, field, None)
+        self.storage = field.storage or source_file.storage
         self.attname = attname
         self.source_file = source_file
 
+    def _require_file(self):
+        if not self.source_file:
+            raise ValueError("The '%s' attribute's image_field has no file associated with it." % self.attname)
+
+    def _get_file(self):
+        self._create(True)
+        return super(ImageFieldFile, self).file
+
+    file = property(_get_file, ImageFieldFile._set_file, ImageFieldFile._del_file)
+
+    @property
+    def url(self):
+        self._create(True)
+        return super(ImageFieldFile, self).url
+
     def _create(self, lazy=False):
         """Creates a new image by running the processors on the source file.
         
@@ -154,12 +167,10 @@ class ImageSpecFile(_ImageSpecFileMixin):
                 a new image should be created and the existing one overwritten.
 
         """
-        img = None
-        if lazy:
-            img = self._img
-            if not img and self.storage.exists(self.name):
-                img = open_image(self.file)
-        if not img and self.source_file: # TODO: Should we error here or something if the source_file doesn't exist?
+        if lazy and (getattr(self, '_file', None) or self.storage.exists(self.name)):
+            return
+
+        if self.source_file: # TODO: Should we error here or something if the source_file doesn't exist?
             # Process the original image file
             try:
                 fp = self.source_file.storage.open(self.source_file.name)
@@ -170,15 +181,35 @@ class ImageSpecFile(_ImageSpecFileMixin):
 
             img, content = self._process_content(self.name, fp)
             self.storage.save(self.name, content)
-        self._img = img
-        return self._img
 
-    def _delete(self):
-        if self.source_file:
-            try:
-                self.storage.delete(self.name)
-            except (NotImplementedError, IOError):
-                return
+    def delete(self, save=False):
+        """Pulled almost verbatim from ``ImageFieldFile.delete()`` and
+        ``FieldFile.delete()`` but with the attempts to reset the instance
+        property removed.
+
+        """
+        # Clear the image dimensions cache
+        if hasattr(self, '_dimensions_cache'):
+            del self._dimensions_cache
+
+        # Only close the file if it's already open, which we know by the
+        # presence of self._file
+        if hasattr(self, '_file'):
+            self.close()
+            del self.file
+
+        try:
+            self.storage.delete(self.name)
+        except (NotImplementedError, IOError):
+            pass
+
+        # Delete the filesize cache
+        if hasattr(self, '_size'):
+            del self._size
+        self._committed = False
+
+        if save:
+            self.instance.save()
 
     @property
     def _suggested_extension(self):
@@ -219,35 +250,13 @@ class ImageSpecFile(_ImageSpecFileMixin):
 
             return new_filename
 
-    @property
-    def storage(self):
-        return self.field.storage or self.source_file.storage
-
-    @property
-    def url(self):
-        if not self.field.pre_cache:
-            self._create(True)
-        return self.storage.url(self.name)
-
-    @property
-    def file(self):
-        if not self._file:
-            if not self.storage.exists(self.name):
-                self._create()
-            self._file = self.storage.open(self.name)
-        return self._file
-
-    @property
-    def image(self):
-        return self._create(True)
-
-    @property
-    def width(self):
-        return self.image.size[0]
-
-    @property
-    def height(self):
-        return self.image.size[1]
+    @name.setter
+    def name(self, value):
+        # TODO: Figure out a better way to handle this. We really don't want to
+        # allow anybody to set the name, but ``File.__init__`` (which is called
+        # by ``ImageSpecFile.__init__``) does, so we have to allow it at least
+        # that one time.
+        pass
 
 
 class _ImageSpecDescriptor(object):
@@ -292,7 +301,7 @@ def _post_save_handler(sender, instance=None, created=False, raw=False, **kwargs
     spec_files = get_spec_files(instance)
     for spec_file in spec_files:
         if not created:
-            spec_file._delete()
+            spec_file.delete(save=False)
         if spec_file.field.pre_cache:
             spec_file._create()
 
@@ -301,7 +310,7 @@ def _post_delete_handler(sender, instance=None, **kwargs):
     assert instance._get_pk_val() is not None, "%s object can't be deleted because its %s attribute is set to None." % (instance._meta.object_name, instance._meta.pk.attname)
     spec_files = get_spec_files(instance)
     for spec_file in spec_files:
-        spec_file._delete()
+        spec_file.delete(save=False)
 
 
 class ProcessedImageFieldFile(ImageFieldFile, _ImageSpecFileMixin):