bpo-41900: C14N 2.0 serialisation failed for unprefixed attributes when a default namespace was defined. (GH-22474)
diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index d22c35d9..3f1f378 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -3899,6 +3899,14 @@
#self.assertEqual(c14n_roundtrip("<doc xmlns:x='http://example.com/x' xmlns='http://example.com/default'><b y:a1='1' xmlns='http://example.com/default' a3='3' xmlns:y='http://example.com/y' y:a2='2'/></doc>"),
#'<doc xmlns:x="http://example.com/x"><b xmlns:y="http://example.com/y" a3="3" y:a1="1" y:a2="2"></b></doc>')
+ # Namespace issues
+ xml = '<X xmlns="http://nps/a"><Y targets="abc,xyz"></Y></X>'
+ self.assertEqual(c14n_roundtrip(xml), xml)
+ xml = '<X xmlns="http://nps/a"><Y xmlns="http://nsp/b" targets="abc,xyz"></Y></X>'
+ self.assertEqual(c14n_roundtrip(xml), xml)
+ xml = '<X xmlns="http://nps/a"><Y xmlns:b="http://nsp/b" b:targets="abc,xyz"></Y></X>'
+ self.assertEqual(c14n_roundtrip(xml), xml)
+
def test_c14n_exclusion(self):
xml = textwrap.dedent("""\
<root xmlns:x="http://example.com/x">
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index da2bcad..7a26900 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -1876,6 +1876,11 @@
self._declared_ns_stack[-1].append((uri, prefix))
return f'{prefix}:{tag}' if prefix else tag, tag, uri
+ if not uri:
+ # As soon as a default namespace is defined,
+ # anything that has no namespace (and thus, no prefix) goes there.
+ return tag, tag, uri
+
raise ValueError(f'Namespace "{uri}" is not declared in scope')
def data(self, data):