Fixed an unhandled exception when formatting a Tag that had been decomposed.[bug=1857767]

3 files changed, 24 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 2758e62..5f32a57 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+= Unreleased
+
+* Fixed an unhandled exception when formatting a Tag that had been
+  decomposed.[bug=1857767]
+
 = 4.8.2 (20191224)
 
 * Added Python docstrings to all public methods of the most commonly
diff --git a/bs4/formatter.py b/bs4/formatter.py
index 09d15e7..9a692ec 100644
--- a/bs4/formatter.py
+++ b/bs4/formatter.py
@@ -108,6 +108,8 @@ class Formatter(EntitySubstitution):
         behavior consistent between Python 2 and Python 3, and preserves
         backwards compatibility with older versions of Beautiful Soup.
         """
+        if tag.attrs is None:
+            return []
         return sorted(tag.attrs.items())
 
    
diff --git a/bs4/tests/test_tree.py b/bs4/tests/test_tree.py
index 7d8da01..3251e0e 100644
--- a/bs4/tests/test_tree.py
+++ b/bs4/tests/test_tree.py
@@ -1777,6 +1777,23 @@ class TestEncoding(SoupTest):
 
 class TestFormatter(SoupTest):
 
+    def test_default_attributes(self):
+        # Test the default behavior of Formatter.attributes().
+        formatter = Formatter()
+        tag = Tag(name="tag")
+        tag['b'] = 1
+        tag['a'] = 2
+
+        # Attributes come out sorted by name. In Python 3, attributes
+        # normally come out of a dictionary in the order they were
+        # added.
+        self.assertEquals([('a', 2), ('b', 1)], formatter.attributes(tag))
+
+        # This works even if Tag.attrs is None, though this shouldn't
+        # normally happen.
+        tag.attrs = None
+        self.assertEquals([], formatter.attributes(tag))
+        
     def test_sort_attributes(self):
         # Test the ability to override Formatter.attributes() to,
         # e.g., disable the normal sorting of attributes.