Set cache expire headers to two months on frontend image serve view

.travis.yml

@@ -14,7 +14,7 @@ services:
 # Package installation
 install:
   - python setup.py install
-  - pip install psycopg2 elasticsearch wand embedly
+  - pip install psycopg2 elasticsearch wand embedly mock python-dateutil
   - pip install coveralls
 # Pre-test configuration
 before_script:

requirements-dev.txt

@@ -2,3 +2,4 @@
 coverage==3.7.1
 flake8==2.2.1
 mock==1.0.1
+python-dateutil==2.2

tox.ini

@@ -3,6 +3,7 @@ dj16=
     Django>=1.6,<1.7
     elasticsearch==1.1.0
     mock==1.0.1
+    python-dateutil==2.2
 
 [tox]
 envlist =

wagtail/wagtailimages/tests.py

@@ -1,9 +1,12 @@
 import json
+import datetime
 
 from mock import MagicMock
+import dateutil.parser
 
 from django.utils import six
 from django.utils.http import urlquote
+from django.utils import timezone
 from django.test import TestCase
 from django import template
 from django.contrib.auth.models import User, Group, Permission
@@ -538,6 +541,14 @@ def test_get(self):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response['Content-Type'], 'image/jpeg')
 
+        # Make sure the cache headers are set to expire after at least one month
+        self.assertIn('Cache-Control', response)
+        self.assertEqual(response['Cache-Control'].split('=')[0], 'max-age')
+        self.assertTrue(int(response['Cache-Control'].split('=')[1]) > datetime.timedelta(days=30).seconds)
+
+        self.assertIn('Expires', response)
+        self.assertTrue(dateutil.parser.parse(response['Expires']) > timezone.now() + datetime.timedelta(days=30))
+
     def test_get_invalid_signature(self):
         """
         Test that an invalid signature returns a 403 response

wagtail/wagtailimages/views/frontend.py

@@ -1,12 +1,14 @@
 from django.shortcuts import get_object_or_404
 from django.http import HttpResponse
 from django.core.exceptions import PermissionDenied
+from django.views.decorators.cache import cache_page
 
 from wagtail.wagtailimages.models import get_image_model
 from wagtail.wagtailimages.utils import InvalidFilterSpecError, verify_signature
 from wagtail.wagtailimages import image_processor
 
 
+@cache_page(60 * 60 * 24 * 60) # Cache for 60 days
 def serve(request, signature, image_id, filter_spec):
     image = get_object_or_404(get_image_model(), id=image_id)