add whether resource is on same domain is now side effect free

ckan/controllers/package.py

@@ -1337,7 +1337,7 @@ def resource_datapreview(self, id, resource_id):
             c.package = get_action('package_show')(context, {'id': id})
 
             data_dict = {'resource': c.resource, 'package': c.package}
-            data_dict = h.add_whether_on_same_domain(data_dict)
+            data_dict['resource']['on_same_domain'] = h.resource_is_on_same_domain(data_dict)
 
             plugins = p.PluginImplementations(p.IResourcePreview)
             plugins_that_can_preview = [plugin for plugin in plugins if plugin.can_preview(data_dict)]

ckan/lib/helpers.py

@@ -1286,18 +1286,12 @@ def _compare_domains(urls):
     return True
 
 
-def add_whether_on_same_domain(data_dict):
-    ''' sets the ``on_same_domain`` flag to a resource dictionary
-    to true if the resource is on the ckan instance domain
-    '''
+def resource_is_on_same_domain(data_dict):
     # compare CKAN domain and resource URL
     ckan_url = config.get('ckan.site_url', '//localhost:5000')
     resource_url = data_dict['resource']['url']
 
-    on_same_domain = _compare_domains([ckan_url, resource_url])
-
-    data_dict['resource']['on_same_domain'] = on_same_domain
-    return data_dict
+    return _compare_domains([ckan_url, resource_url])
 
 
 def _can_be_previewed(data_dict):
@@ -1308,7 +1302,7 @@ def _can_be_previewed(data_dict):
         The resource dict has to have a value for ``on_same_domain``
     :type data_dict: dictionary
     '''
-    data_dict = add_whether_on_same_domain(data_dict)
+    data_dict['resource']['on_same_domain'] = resource_is_on_same_domain(data_dict)
     plugins = p.PluginImplementations(p.IResourcePreview)
     return any(plugin.can_preview(data_dict) for plugin in plugins)