Allow disabling deletion of image files and thumbnails

Oscar by default deleted image files and thumbnails. That is usually
fine, but has been an issue when using remote storages like S3. This
change also makes the only remaining import from sorl optional, hence
paving the way to making it completely optional.

Fixes #1373.

docs/source/ref/settings.rst

@@ -85,7 +85,7 @@ The number of products to paginate by.
 .. _oscar_search_facets:
 
 ``OSCAR_SEARCH_FACETS``
-------------------------------
+-----------------------
 
 A dictionary that specifies the facets to use with the search backend.  It
 needs to be a dict with keys ``fields`` and ``queries`` for field- and
@@ -405,6 +405,15 @@ The folder name can contain date format strings as described in the `Django Docs
 
 .. _`Django Docs`: https://docs.djangoproject.com/en/dev/ref/models/fields/#filefield
 
+``OSCAR_DELETE_IMAGE_FILES``
+----------------------------
+
+Default: ``True``
+
+If enabled, a ``post_delete`` hook will attempt to delete any image files and
+created thumbnails when a model with an ``ImageField`` is deleted. This is
+usually desired, but might not be what you want when using a remote storage.
+
 
 ``OSCAR_PROMOTION_FOLDER``
 --------------------------

docs/source/releases/v0.8.rst

@@ -171,6 +171,11 @@ Minor changes
 * The forms for the order dashboard views are now loaded dynamically so they
   can be overridden.
 
+* Introduced a ``OSCAR_DELETE_IMAGE_FILES`` settings which makes deleting
+  image files and thumbnails upon deleting of a model with an ``ImageField``
+  optional. It usually is desired behaviour, but can slow down an app when
+  using a remote storage.
+
 .. _incompatible_changes_in_0.8:
 
 Backwards incompatible changes in 0.8

oscar/apps/catalogue/receivers.py

@@ -1,33 +1,37 @@
 # -*- coding: utf-8 -*-
-from oscar.core.loading import get_model
-
-from django.db import models
-from django.db.models.signals import post_delete
-
-from sorl import thumbnail
-from sorl.thumbnail.helpers import ThumbnailError
-
-ProductImage = get_model('catalogue', 'ProductImage')
-Category = get_model('catalogue', 'Category')
-
-
-def delete_image_files(sender, instance, **kwargs):
-    """
-    Deletes the original image, created thumbnails, and any entries
-    in sorl's key-value store.
-    """
-    image_fields = (models.ImageField, thumbnail.ImageField)
-    for field in instance._meta.fields:
-        if isinstance(field, image_fields):
-            # Make Django return ImageFieldFile instead of ImageField
-            fieldfile = getattr(instance, field.name)
-            try:
-                thumbnail.delete(fieldfile)
-            except ThumbnailError:
-                pass
-
-
-# connect for all models with ImageFields - add as needed
-models_with_images = [ProductImage, Category]
-for sender in models_with_images:
-    post_delete.connect(delete_image_files, sender=sender)
+
+from django.conf import settings
+
+if settings.OSCAR_DELETE_IMAGE_FILES:
+
+    from oscar.core.loading import get_model
+
+    from django.db import models
+    from django.db.models.signals import post_delete
+
+    from sorl import thumbnail
+    from sorl.thumbnail.helpers import ThumbnailError
+
+    ProductImage = get_model('catalogue', 'ProductImage')
+    Category = get_model('catalogue', 'Category')
+
+    def delete_image_files(sender, instance, **kwargs):
+        """
+        Deletes the original image, created thumbnails, and any entries
+        in sorl's key-value store.
+        """
+        image_fields = (models.ImageField, thumbnail.ImageField)
+        for field in instance._meta.fields:
+            if isinstance(field, image_fields):
+                # Make Django return ImageFieldFile instead of ImageField
+                fieldfile = getattr(instance, field.name)
+                try:
+                    thumbnail.delete(fieldfile)
+                except ThumbnailError:
+                    pass
+
+
+    # connect for all models with ImageFields - add as needed
+    models_with_images = [ProductImage, Category]
+    for sender in models_with_images:
+        post_delete.connect(delete_image_files, sender=sender)

oscar/defaults.py

@@ -22,6 +22,7 @@ OSCAR_DEFAULT_CURRENCY = 'GBP'
 # Paths
 OSCAR_IMAGE_FOLDER = 'images/products/%Y/%m/'
 OSCAR_PROMOTION_FOLDER = 'images/promotions/'
+OSCAR_DELETE_IMAGE_FILES = True
 
 # Copy this image from oscar/static/img to your MEDIA_ROOT folder.
 # It needs to be there so Sorl can resize it.