gh-140601: Add ResourceWarning to iterparse when not closed

Doc/library/xml.etree.elementtree.rst

@@ -656,6 +656,10 @@ Functions
  .. versionchanged:: 3.13
  Added the :meth:`!close` method.
 
+ .. versionchanged:: next
+ A :exc:`ResourceWarning` is now emitted if the iterator opened a file
+ and is not explicitly closed.
+
 
 .. function:: parse(source, parser=None)
 

Doc/whatsnew/3.15.rst

@@ -1150,3 +1150,9 @@ that may require changes to your code.
 
 * :meth:`~mmap.mmap.resize` has been removed on platforms that don't support the
  underlying syscall, instead of raising a :exc:`SystemError`.
+
+* Resource warning is now emitted for unclosed
+ :func:`xml.etree.ElementTree.iterparse` iterator if it opened a file.
+ Use its :meth:`!close` method or the :func:`contextlib.closing` context
+ manager to close it.
+ (Contributed by Osama Abdelkader and Serhiy Storchaka in :gh:`140601`.)

Lib/test/test_xml_etree.py

@@ -1436,18 +1436,40 @@ def test_nonexistent_file(self):
 
  def test_resource_warnings_not_exhausted(self):
  # Not exhausting the iterator still closes the underlying file (bpo-43292)
+ # Not closing before del should emit ResourceWarning
  it = ET.iterparse(SIMPLE_XMLFILE)
  with warnings_helper.check_no_resource_warning(self):
+ it.close()
+ del it
+ gc_collect()
+
+ it = ET.iterparse(SIMPLE_XMLFILE)
+ with self.assertWarns(ResourceWarning) as wm:
  del it
  gc_collect()
+ # Not 'unclosed file'.
+ self.assertIn('unclosed iterparse iterator', str(wm.warning))
+ self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+ self.assertEqual(wm.filename, __file__)
 
  it = ET.iterparse(SIMPLE_XMLFILE)
  with warnings_helper.check_no_resource_warning(self):
  action, elem = next(it)
+ it.close()
  self.assertEqual((action, elem.tag), ('end', 'element'))
  del it, elem
  gc_collect()
 
+ it = ET.iterparse(SIMPLE_XMLFILE)
+ with self.assertWarns(ResourceWarning) as wm:
+ action, elem = next(it)
+ self.assertEqual((action, elem.tag), ('end', 'element'))
+ del it, elem
+ gc_collect()
+ self.assertIn('unclosed iterparse iterator', str(wm.warning))
+ self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+ self.assertEqual(wm.filename, __file__)
+
  def test_resource_warnings_failed_iteration(self):
  self.addCleanup(os_helper.unlink, TESTFN)
  with open(TESTFN, "wb") as f:
@@ -1461,15 +1483,40 @@ def test_resource_warnings_failed_iteration(self):
  next(it)
  self.assertEqual(str(cm.exception),
  'junk after document element: line 1, column 12')
+ it.close()
  del cm, it
  gc_collect()
 
+ it = ET.iterparse(TESTFN)
+ action, elem = next(it)
+ self.assertEqual((action, elem.tag), ('end', 'document'))
+ with self.assertWarns(ResourceWarning) as wm:
+ with self.assertRaises(ET.ParseError) as cm:
+ next(it)
+ self.assertEqual(str(cm.exception),
+ 'junk after document element: line 1, column 12')
+ del cm, it
+ gc_collect()
+ self.assertIn('unclosed iterparse iterator', str(wm.warning))
+ self.assertIn(repr(TESTFN), str(wm.warning))
+ self.assertEqual(wm.filename, __file__)
+
  def test_resource_warnings_exhausted(self):
  it = ET.iterparse(SIMPLE_XMLFILE)
  with warnings_helper.check_no_resource_warning(self):
+ list(it)
+ it.close()
+ del it
+ gc_collect()
+
+ it = ET.iterparse(SIMPLE_XMLFILE)
+ with self.assertWarns(ResourceWarning) as wm:
  list(it)
  del it
  gc_collect()
+ self.assertIn('unclosed iterparse iterator', str(wm.warning))
+ self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+ self.assertEqual(wm.filename, __file__)
 
  def test_close_not_exhausted(self):
  iterparse = ET.iterparse

Lib/xml/etree/ElementTree.py

@@ -1261,16 +1261,20 @@ def iterator(source):
  gen = iterator(source)
  class IterParseIterator(collections.abc.Iterator):
  __next__ = gen.__next__
+
  def close(self):
+ nonlocal close_source
  if close_source:
  source.close()
+ close_source = False
  gen.close()
 
- def __del__(self):
- # TODO: Emit a ResourceWarning if it was not explicitly closed.
- # (When the close() method will be supported in all maintained Python versions.)
+ def __del__(self, _warn=warnings.warn):
  if close_source:
- source.close()
+ try:
+ _warn(f"unclosed iterparse iterator{source.name!r}", ResourceWarning, stacklevel=2)
+ finally:
+ source.close()
 
  it = IterParseIterator()
  it.root = None

Misc/NEWS.d/next/Library/2025-10-25-22-55-07.gh-issue-140601.In3MlS.rst

@@ -0,0 +1,4 @@
+:func:`xml.etree.ElementTree.iterparse` now emits a :exc:`ResourceWarning`
+when the iterator is not explicitly closed and was opened with a filename.
+This helps developers identify and fix resource leaks. Patch by Osama
+Abdelkader.