gh-159637: Fix renaming an attribute to a prefixed name in minidom

Document.renameNode() set the new prefix of an attribute before its
new namespace, so the prefix was validated against the old namespace.
Renaming an attribute with no namespace to a prefixed name in a
namespace raised NamespaceErr after the attribute had been removed
from its element.

Set the namespace first, and check the prefix before removing the
attribute, so that a rejected rename leaves the element unchanged.

Author: fedonman

Lib/test/test_minidom.py

@@ -1880,6 +1880,28 @@ def testRenameAttribute(self):
         self.checkRenameNodeSharedConstraints(doc, attr)
         doc.unlink()
 
+    def testRenameAttributeToPrefixedName(self):
+        doc = parseString("<doc a='v' b='w'/>")
+        elem = doc.documentElement
+        attr = elem.getAttributeNode("a")
+        attr = doc.renameNode(attr, "http://xml.python.org/ns", "p:c")
+        self.assertEqual(attr.name, "p:c")
+        self.assertEqual(attr.prefix, "p")
+        self.assertEqual(attr.localName, "c")
+        self.assertEqual(attr.namespaceURI, "http://xml.python.org/ns")
+        self.assertIsNone(elem.getAttributeNode("a"))
+        self.assertIs(elem.getAttributeNodeNS("http://xml.python.org/ns", "c"),
+                      attr)
+
+        # A rejected rename leaves the attribute on its element.
+        attr = elem.getAttributeNode("b")
+        self.assertRaises(xml.dom.NamespaceErr, doc.renameNode, attr,
+                          "http://xml.python.org/ns", "xml:lang")
+        self.assertEqual(attr.name, "b")
+        self.assertIsNone(attr.namespaceURI)
+        self.assertIs(elem.getAttributeNode("b"), attr)
+        doc.unlink()
+
     def testRenameElement(self):
         doc = parseString("<doc/>")
         elem = doc.documentElement

Lib/xml/dom/minidom.py

@@ -2129,15 +2129,17 @@ def renameNode(self, n, namespaceURI, name):
             prefix = None
             localName = None
         if n.nodeType == Node.ATTRIBUTE_NODE:
+            if prefix is not None:
+                _check_prefix(prefix, namespaceURI, True)
             element = n.ownerElement
             if element is not None:
                 is_id = n._is_id
                 element.removeAttributeNode(n)
         else:
             element = None
+        n.namespaceURI = namespaceURI
         n.prefix = prefix
         n._localName = localName
-        n.namespaceURI = namespaceURI
         n.nodeName = name
         if n.nodeType == Node.ELEMENT_NODE:
             n.tagName = name