Backwards compatibility for 3-argument run methods

wagtail/wagtailimages/models.py

@@ -1,7 +1,9 @@
 from __future__ import absolute_import, unicode_literals
 
 import hashlib
+import inspect
 import os.path
+import warnings
 from collections import OrderedDict
 from contextlib import contextmanager
 
@@ -25,6 +27,7 @@ from taggit.managers import TaggableManager
 from unidecode import unidecode
 from willow.image import Image as WillowImage
 
+from wagtail.utils.deprecation import RemovedInWagtail19Warning
 from wagtail.wagtailadmin.utils import get_object_usage
 from wagtail.wagtailcore import hooks
 from wagtail.wagtailcore.models import CollectionMember
@@ -412,7 +415,25 @@ class Filter(models.Model):
 
             env = {}
             for operation in self.operations:
-                willow = operation.run(willow, image, env) or willow
+                # Check that the operation can take the new "env" argument
+                # (added in Wagtail 1.5)
+                try:
+                    inspect.getcallargs(operation.run, willow, image, env)
+                    accepts_env = True
+                except TypeError:
+                    # Check that the paramters fit the old style, so we don't
+                    # raise a warning if there is a coding error
+                    inspect.getcallargs(operation.run, willow, image)
+                    accepts_env = False
+                    warnings.warn("ImageOperation run methods should take 4 "
+                                  "arguments. %d.run only takes 3.",
+                                  RemovedInWagtail19Warning)
+
+                # Call operation
+                if accepts_env:
+                    willow = operation.run(willow, image, env) or willow
+                else:
+                    willow = operation.run(willow, image) or willow
 
             if original_format == 'jpeg':
                 # Allow changing of JPEG compression quality

wagtail/wagtailimages/tests/test_image_operations.py

@@ -1,9 +1,12 @@
 from __future__ import absolute_import, unicode_literals
 
+import warnings
+
 from django.test import TestCase
 from django.utils.six import BytesIO
 from mock import Mock
 
+from wagtail.utils.deprecation import RemovedInWagtail19Warning
 from wagtail.wagtailcore import hooks
 from wagtail.wagtailimages import image_operations
 from wagtail.wagtailimages.exceptions import InvalidFilterSpecError
@@ -394,7 +397,12 @@ class TestFilter(TestCase):
     operation_instance = Mock()
 
     def test_runs_operations(self):
-        self.operation_instance.run = Mock()
+        run_mock = Mock()
+
+        def run(willow, image, env):
+            run_mock(willow, image, env)
+
+        self.operation_instance.run = run
 
         fil = Filter(spec='operation1|operation2')
         image = Image.objects.create(
@@ -403,7 +411,34 @@ class TestFilter(TestCase):
         )
         fil.run(image, BytesIO())
 
-        self.assertEqual(self.operation_instance.run.call_count, 2)
+        self.assertEqual(run_mock.call_count, 2)
+
+    def test_runs_operations_without_env_argument(self):
+        # The "env" argument was added in Wagtial 1.5. This tests that
+        # image operations written for 1.4 will still work
+
+        run_mock = Mock()
+
+        def run(willow, image):
+            run_mock(willow, image)
+
+        self.operation_instance.run = run
+
+        fil = Filter(spec='operation1|operation2')
+        image = Image.objects.create(
+            title="Test image",
+            file=get_test_image_file(),
+        )
+
+        with warnings.catch_warnings(record=True) as ws:
+            warnings.simplefilter('always')
+
+            fil.run(image, BytesIO())
+
+            self.assertEqual(len(ws), 2)
+            self.assertIs(ws[0].category, RemovedInWagtail19Warning)
+
+        self.assertEqual(run_mock.call_count, 2)
 
 
 @hooks.register('register_image_operations')