port atom.py from django templates to jinja2

...in order to (re)drop the app engine dependency.

cc @kylewm @kevinmarks @danlyke re our template discussion last night. not proud of this, but meh. at least the template itself didn't change much! :P

granary/atom.py

@@ -3,18 +3,18 @@
 Atom spec: http://atomenabled.org/developers/syndication/
 """
 
+import collections
 import os
 import re
 import urlparse
 
-import webapp2
-from google.appengine.ext.webapp import template
+import jinja2
 from oauth_dropins.webutil import util
 
 import microformats2
 import source
 
-ATOM_TEMPLATE_FILE = os.path.join(os.path.dirname(__file__), 'templates', 'user_feed.atom')
+ATOM_TEMPLATE_FILE = 'user_feed.atom'
 # stolen from django.utils.html
 UNENCODED_AMPERSANDS_RE = re.compile(r'&(?!(\w+|#\d+);)')
 
@@ -61,14 +61,29 @@ def activities_to_atom(activities, actor, title=None, request_url=None,
       if image and not isinstance(image, list):
         att['image'] = [image]
 
-  return template.render(ATOM_TEMPLATE_FILE, {
-    'items': activities,
-    'host_url': host_url,
-    'request_url': request_url,
-    'title': title or 'User feed for ' + source.Source.actor_name(actor),
-    'updated': activities[0]['object'].get('published') if activities else '',
-    'actor': actor,
-    })
+  # Emulate Django template behavior that returns a special default value that
+  # can continue to be referenced when an attribute or item lookup fails. Helps
+  # avoid conditionals in the template itself.
+  # https://docs.djangoproject.com/en/1.8/ref/templates/language/#variables
+  class Defaulter(collections.defaultdict):
+    def __init__(self, **kwargs):
+      super(Defaulter, self).__init__(Defaulter, **{
+        k: (Defaulter(**v) if isinstance(v, dict) else v)
+        for k, v in kwargs.items()})
+
+    def __unicode__(self):
+      return super(Defaulter, self).__unicode__() if self else u''
+
+  env = jinja2.Environment(loader=jinja2.PackageLoader(__package__, 'templates'),
+                           autoescape=True)
+  return env.get_template(ATOM_TEMPLATE_FILE).render(
+    items=[Defaulter(**a) for a in activities],
+    host_url=host_url,
+    request_url=request_url,
+    title=title or 'User feed for ' + source.Source.actor_name(actor),
+    updated=activities[0]['object'].get('published', '') if activities else '',
+    actor=actor,
+    )
 
 
 def _remove_query_params(url):

granary/templates/user_feed.atom

@@ -16,6 +16,7 @@
 <logo>{{ actor.image.url }}</logo>
 <updated>{{ updated }}</updated>
 {% include "author.atom" %}
+
 <link href="{{ actor.url }}" rel="alternate" type="text/html" />
 <link rel="avatar" href="{{ actor.image.url }}" />
 <link href="{{ request_url }}" rel="self" type="application/atom+xml" />
@@ -26,9 +27,9 @@
 <!-- <link href="{{ salmon_uri }}" rel="http://salmon-protocol.org/ns/salmon-mention" /> -->
 {% for activity in items %}
 <entry>
-{% with activity.actor as actor %}
+{% set actor = activity.actor %}
 {% include "author.atom" %}
-{% endwith %}
+
   <activity:object-type>
     http://activitystrea.ms/schema/1.0/{{ activity.object.objectType }}
   </activity:object-type>
@@ -65,14 +66,14 @@
   {% endfor %}
   <!-- <link rel="ostatus:conversation" href="" /> -->
   <!-- http://www.georss.org/simple -->
-  {% with activity.object.location as location %}
+  {% set location = activity.object.location %}
   {% if location.latitude and location.longitude %}
     <georss:point>{{ location.latitude }} {{location.longitude }}</georss:point>
   {% endif %}
   {% if location.displayName %}
     <georss:featureName>{{ location.displayName }}</georss:featureName>
   {% endif %}
-  {% endwith %}
+
   <link rel="self" type="application/atom+xml" href="{{ activity.url }}" />
 </entry>
 {% endfor %}

requirements.txt

@@ -1,5 +1,6 @@
 # Keep in sync with setup.py's install_requires!
 beautifulsoup4
+jinja2
 mf2py>=0.2.6
 oauth-dropins
 requests

setup.py

@@ -41,6 +41,7 @@ def __init__(self, *args, **kwargs):
       install_requires=[
           # Keep in sync with requirements.txt!
           'beautifulsoup4',
+          'jinja2',
           'mf2py>=0.2.6',
           'oauth-dropins',
           'requests',