Allow an extra path component on image serve view

Currently, we only allow the following format for the serve view:

    /images/<signature/<id>/<filter>/

This URL doesn't look nice as an image is expected to be a standalone file. This commit makes the following format possible:

    /images/<signature/<id>/<filter>/test.jpg

wagtail/wagtailimages/tests/tests.py

@@ -226,6 +226,34 @@ class TestFrontendServeView(TestCase):
         self.assertTrue(response.streaming)
         self.assertEqual(response['Content-Type'], 'image/png')
 
+    def test_get_with_extra_component(self):
+        """
+        Test that a filename can be optionally added to the end of the URL.
+        """
+        # Generate signature
+        signature = generate_signature(self.image.id, 'fill-800x600')
+
+        # Get the image
+        response = self.client.get(reverse('wagtailimages_serve', args=(signature, self.image.id, 'fill-800x600')) + 'test.png')
+
+        # Check response
+        self.assertEqual(response.status_code, 200)
+        self.assertTrue(response.streaming)
+        self.assertEqual(response['Content-Type'], 'image/png')
+
+    def test_get_with_too_many_extra_components(self):
+        """
+        A filename can be appended to the end of the URL, but it must not contain a '/'
+        """
+        # Generate signature
+        signature = generate_signature(self.image.id, 'fill-800x600')
+
+        # Get the image
+        response = self.client.get(reverse('wagtailimages_serve', args=(signature, self.image.id, 'fill-800x600')) + 'test/test.png')
+
+        # URL pattern should not match
+        self.assertEqual(response.status_code, 404)
+
     def test_get_invalid_signature(self):
         """
         Test that an invalid signature returns a 403 response

wagtail/wagtailimages/urls.py

@@ -5,5 +5,5 @@ from django.conf.urls import url
 from wagtail.wagtailimages.views.serve import serve
 
 urlpatterns = [
-    url(r'^(.*)/(\d*)/(.*)/$', serve, name='wagtailimages_serve'),
+    url(r'^([^/]*)/(\d*)/([^/]*)/[^/]*$', serve, name='wagtailimages_serve'),
 ]