Namespace prefix is preserved when an XML tag is copied. Thanks

  to Vikas for a patch and test. [bug=1685172]

2 files changed, 12 insertions, 2 deletions

diff --git a/bs4/element.py b/bs4/element.py
index 526db28..9ef75f8 100644
--- a/bs4/element.py
+++ b/bs4/element.py
@@ -870,7 +870,7 @@ class Tag(PageElement):
         Its contents are a copy of the old Tag's contents.
         """
         clone = type(self)(None, self.builder, self.name, self.namespace,
-                           self.nsprefix, self.attrs, is_xml=self._is_xml)
+                           self.prefix, self.attrs, is_xml=self._is_xml)
         for attr in ('can_be_empty_element', 'hidden'):
             setattr(clone, attr, getattr(self, attr))
         for child in self.contents:
diff --git a/bs4/testing.py b/bs4/testing.py
index 40ccac6..6ba2506 100644
--- a/bs4/testing.py
+++ b/bs4/testing.py
@@ -710,8 +710,18 @@ class XMLTreeBuilderSmokeTest(object):
         self.assertEqual(1, len(soup.find_all('ns2:tag', key='value')))
         self.assertEqual(3, len(soup.find_all(['ns1:tag', 'ns2:tag'])))
         
+    def test_copy_tag_preserves_namespace(self):
+        xml = """<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<w:document xmlns:w="http://example.com/ns0"/>"""
+    
+        soup = self.soup(xml)
+        tag = soup.document
+        duplicate = copy.copy(tag)
+
+        # The two tags have the same namespace prefix.
+        self.assertEqual(tag.prefix, duplicate.prefix)
+
 
-        
 class HTML5TreeBuilderSmokeTest(HTMLTreeBuilderSmokeTest):
     """Smoke test for a tree builder that supports HTML5."""