RSS: sort and display feed items by date

plugins/RSS/config.py

@@ -45,6 +45,10 @@ def configure(advanced):
 class FeedNames(registry.SpaceSeparatedListOfStrings):
     List = callbacks.CanonicalNameSet
 
+class FeedItemSortOrder(registry.OnlySomeStrings):
+    """Valid values include 'asInFeed', 'oldestFirst', 'newestFirst'."""
+    validStrings = ('asInFeed', 'oldestFirst', 'newestFirst')
+
 RSS = conf.registerPlugin('RSS')
 conf.registerChannelValue(RSS, 'bold', registry.Boolean(
     True, _("""Determines whether the bot will bold the title of the feed when
@@ -64,6 +68,10 @@ conf.registerGlobalValue(RSS, 'waitPeriod',
     registry.PositiveInteger(1800, _("""Indicates how many seconds the bot will
     wait between retrieving RSS feeds; requests made within this period will
     return cached results.""")))
+conf.registerGlobalValue(RSS, 'sortFeedItems',
+    FeedItemSortOrder('asInFeed', _("""Determines whether feed items should be
+    sorted by their update timestamp or kept in the same order as they appear
+    in a feed.""")))
 conf.registerGlobalValue(RSS, 'feeds',
     FeedNames([], _("""Determines what feeds should be accessible as
     commands.""")))

plugins/RSS/plugin.py

@@ -300,11 +300,27 @@ class RSS(callbacks.Plugin):
             return conv
         else:
             return lambda s: toText(s).strip()
+    def _sortFeedItems(self, items):
+        """Return feed items, sorted according to sortFeedItems."""
+        order = self.registryValue('sortFeedItems')
+        if order not in ['oldestFirst', 'newestFirst']:
+            return items
+        if order == 'oldestFirst':
+            reverse = False
+        if order == 'newestFirst':
+            reverse = True
+        try:
+            sitems = sorted(items, key=lambda i: i['updated'], reverse=reverse)
+        except KeyError:
+            # feedparser normalizes required timestamp fields in ATOM and RSS
+            # to the "updated" field. Feeds missing it are unsortable by date.
+            return items
+        return sitems
 
     def getHeadlines(self, feed):
         headlines = []
         conv = self._getConverter(feed)
-        for d in feed['items']:
+        for d in self._sortFeedItems(feed['items']):
             if 'title' in d:
                 title = conv(d['title'])
                 link = d.get('link')