Avoid a crash when unpickling certain parse trees generated using html5lib on Python 3. [bug=1843545]

3 files changed, 13 insertions, 7 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 3551449..1b6a95d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,6 +6,11 @@
   and position within a line (Tag.sourcepos).  Based on code by Chris
   Mayo. [bug=1742921]
 
+* When instantiating a BeautifulSoup object, it's now possible to
+   provide replacement classes to be instantiated for every tag ('tag_class')
+   or string ('string_class') encountered during parsing, rather than
+   using the default Tag and NavigableString objects.
+
 * Fixed the definition of the default XML namespace when using
    lxml 4.4. Patch by Isaac Muse. [bug=1840141]
 
@@ -15,17 +20,15 @@
 * Copying a Tag preserves information that was originally obtained from
    the TreeBuilder used to build the original Tag. [bug=1838903]
 
-* When instantiating a BeautifulSoup object, it's now possible to
-   provide replacement classes to be instantiated for every tag ('tag_class')
-   or string ('string_class') encountered during parsing, rather than
-   using the default Tag and NavigableString objects.
-
 * Raise an explanatory exception when the underlying parser
    completely rejects the incoming markup. [bug=1838877]
 
 * Avoid a crash when trying to detect the declared encoding of a
    Unicode document. [bug=1838877]
 
+* Avoid a crash when unpickling certain parse trees generated
+   using html5lib on Python 3. [bug=1843545]
+
 = 4.8.0 (20190720, "One Small Soup")
 
 This release focuses on making it easier to customize Beautiful Soup's
diff --git a/bs4/element.py b/bs4/element.py
index d6ed020..2001ad5 100644
--- a/bs4/element.py
+++ b/bs4/element.py
@@ -45,7 +45,7 @@ def _alias(attr):
 
 class NamespacedAttribute(unicode):
 
-    def __new__(cls, prefix, name, namespace=None):
+    def __new__(cls, prefix, name=None, namespace=None):
         if not name:
             # This is the default namespace. Its name "has no value"
             # per https://www.w3.org/TR/xml-names/#defaulting
diff --git a/bs4/tests/test_soup.py b/bs4/tests/test_soup.py
index 3603e81..dc88662 100644
--- a/bs4/tests/test_soup.py
+++ b/bs4/tests/test_soup.py
@@ -638,10 +638,13 @@ class TestUnicodeDammit(unittest.TestCase):
             
 class TestNamedspacedAttribute(SoupTest):
 
-    def test_name_may_be_none(self):
+    def test_name_may_be_none_or_missing(self):
         a = NamespacedAttribute("xmlns", None)
         self.assertEqual(a, "xmlns")
 
+        a = NamespacedAttribute("xmlns")
+        self.assertEqual(a, "xmlns")
+        
     def test_attribute_is_equivalent_to_colon_separated_string(self):
         a = NamespacedAttribute("a", "b")
         self.assertEqual("a:b", a)