Fix double subtitles if description & subtitle are provided

Tests all four possible combinations against the expected result.

2 files changed, 51 insertions, 2 deletions

diff --git a/feedgenerator/django/utils/feedgenerator.py b/feedgenerator/django/utils/feedgenerator.py
index b5d858c..6631788 100644
--- a/feedgenerator/django/utils/feedgenerator.py
+++ b/feedgenerator/django/utils/feedgenerator.py
@@ -325,10 +325,10 @@ class Atom1Feed(SyndicationFeed):
             handler.endElement("author")
         # try to use description or subtitle if provided, subtitle has
         # precedence above description
-        if self.feed['description'] is not None:
-            handler.addQuickElement("subtitle", self.feed['description'])
         if self.feed['subtitle'] is not None:
             handler.addQuickElement("subtitle", self.feed['subtitle'])
+        elif self.feed['description'] is not None:
+            handler.addQuickElement("subtitle", self.feed['description'])
         for cat in self.feed['categories']:
             handler.addQuickElement("category", "", {"term": cat})
         if self.feed['feed_copyright'] is not None:
diff --git a/tests_feedgenerator/test_feedgenerator.py b/tests_feedgenerator/test_feedgenerator.py
index 6ec28aa..7370954 100644
--- a/tests_feedgenerator/test_feedgenerator.py
+++ b/tests_feedgenerator/test_feedgenerator.py
@@ -96,3 +96,52 @@ class TestFeedGenerator(unittest.TestCase):
         expected_result = build_expected_atom_result(feed, EXPECTED_RESULT_ATOM, None)
         self.assertEqual(type(result), type(expected_result))
         self.assertEqual(result, expected_result)
+
+    def test_subtitle(self):
+        """Test regression for https://github.com/getpelican/feedgenerator/issues/30.
+
+        """
+        # case 1: neither should be in
+        FIXT_FEED = dict(
+            title="title",
+            link="https://example.com",
+            description=None,
+            subtitle=None,
+        )
+        feed = feedgenerator.Atom1Feed(**FIXT_FEED)
+        result = feed.writeString(ENCODING)
+        assert "<desciption></description>" not in result
+
+        # case 2: only description should be in
+        FIXT_FEED = dict(
+            title="title",
+            link="https://example.com",
+            description="description",
+            subtitle=None,
+        )
+        feed = feedgenerator.Atom1Feed(**FIXT_FEED)
+        result = feed.writeString(ENCODING)
+        assert "<subtitle>description</subtitle>" in result
+
+        # case 3: only subtitle should be in
+        FIXT_FEED = dict(
+            title="title",
+            link="https://example.com",
+            description=None,
+            subtitle="subtitle",
+        )
+        feed = feedgenerator.Atom1Feed(**FIXT_FEED)
+        result = feed.writeString(ENCODING)
+        assert "<subtitle>subtitle</subtitle>" in result
+
+        # case 4: both are in, only subtitle should be in
+        FIXT_FEED = dict(
+            title="title",
+            link="https://example.com",
+            description="description",
+            subtitle="subtitle",
+        )
+        feed = feedgenerator.Atom1Feed(**FIXT_FEED)
+        result = feed.writeString(ENCODING)
+        assert "<subtitle>subtitle</subtitle>" in result
+        assert "<subtitle>description</subtitle>" not in result