Convert atom feeds to use feedgenerator library.

Issue is that Werkzeug > 1.0.0 has removed werkzeug.contrib.atom.AtomFeed,
making it difficult to use a distribution-packaged version of werkzeug. To solve
this, I've replaced use of werkzeug.contrib.atom.AtomFeed with
feedgenerator.Atom1Feed.

After the change, the only major difference between the feeds before and after is
that they use <summary> instead of <content>. Minor differences include no longer
adding 'type="text/html"' on some <link> elements and no "xml:base" attribute on
<entry> elements. I don't think these differences will have any noticable
effect.

Tested on Liferea feed reader.

1 files changed, 38 insertions, 0 deletions

diff --git a/mediagoblin/tools/feeds.py b/mediagoblin/tools/feeds.py
new file mode 100644
index 00000000..c62478c4
--- /dev/null
+++ b/mediagoblin/tools/feeds.py
@@ -0,0 +1,38 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2021 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from feedgenerator.django.utils import feedgenerator
+
+
+class AtomFeedWithLinks(feedgenerator.Atom1Feed):
+    """Custom AtomFeed that adds additional top-level links.
+
+    This is used in MediaGoblin for adding pubsubhubub "hub" links to the feed
+    via the "push_urls" config. We're porting the feed across to feedgenerator
+    due to deprecation of werkzeug.contrib.atom.AtomFeed, so while I've never
+    seen this feature in use, but this class allows us to continue to support
+    it.
+
+    """
+    def __init__(self, *args, links=None, **kwargs):
+        super().__init__(*args, **kwargs)
+        links = [] if links is None else links
+        self.links = links
+
+    def add_root_elements(self, handler):
+        super().add_root_elements(handler)
+        for link in self.links:
+            handler.addQuickElement('link', '', link)