gh-142145: Remove quadratic behavior in node ID cache clearing

Lib/test/test_minidom.py

@@ -2,6 +2,7 @@
 
 import copy
 import pickle
+import time
 import io
 from test import support
 import unittest
@@ -173,6 +174,23 @@ def testAppendChild(self):
  self.assertEqual(dom.documentElement.childNodes[-1].data, "Hello")
  dom.unlink()
 
+ def testAppendChildNoQuadraticComplexity(self):
+ impl = getDOMImplementation()
+
+ newdoc = impl.createDocument(None, "some_tag", None)
+ top_element = newdoc.documentElement
+ children = [newdoc.createElement(f"child-{i}") for i in range(1, 2 ** 15 + 1)]
+ element = top_element
+
+ start = time.time()
+ for child in children:
+ element.appendChild(child)
+ element = child
+ end = time.time()
+
+ # This example used to take at least 30 seconds.
+ self.assertLess(end - start, 1)
+
  def testAppendChildFragment(self):
  dom, orig, c1, c2, c3, frag = self._create_fragment_test_nodes()
  dom.documentElement.appendChild(frag)

Lib/xml/dom/minidom.py

@@ -292,13 +292,6 @@ def _append_child(self, node):
 childNodes.append(node)
 node.parentNode=self
 
-def_in_document(node):
-# return True iff node is part of a document tree
-whilenodeisnotNone:
-ifnode.nodeType==Node.DOCUMENT_NODE:
-returnTrue
-node=node.parentNode
-returnFalse
 
 def_write_data(writer, text, attr):
 "Writes datachars to writer."
@@ -1555,7 +1548,7 @@ def _clear_id_cache(node):
 ifnode.nodeType==Node.DOCUMENT_NODE:
 node._id_cache.clear()
 node._id_search_stack=None
-elif_in_document(node):
+elifnode.ownerDocument:
 node.ownerDocument._id_cache.clear()
 node.ownerDocument._id_search_stack=None
 

Misc/NEWS.d/next/Security/2025-12-01-09-36-45.gh-issue-142145.tcAUhg.rst

@@ -0,0 +1 @@
+Remove quadratic behavior in ``xml.minidom`` node ID cache clearing.