bpo-43292: Fix file leak in ET.iterparse() when not exhausted (GH-31696)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Author: jacobtylerwalls

Lib/test/test_xml_etree.py

@@ -658,6 +658,14 @@ def test_iterparse(self):
  'junk after document element: line 1, column 12')
  del cm, it
 
+ # Not exhausting the iterator still closes the resource (bpo-43292)
+ with warnings_helper.check_no_resource_warning(self):
+ it = iterparse(TESTFN)
+ del it
+
+ with self.assertRaises(FileNotFoundError):
+ iterparse("nonexistent")
+
  def test_writefile(self):
  elem = ET.Element("tag")
  elem.text = "text"

Lib/xml/etree/ElementTree.py

@@ -1244,8 +1244,14 @@ def iterparse(source, events=None, parser=None):
  # Use the internal, undocumented _parser argument for now; When the
  # parser argument of iterparse is removed, this can be killed.
  pullparser = XMLPullParser(events=events, _parser=parser)
- def iterator():
+
+ def iterator(source):
+ close_source = False
  try:
+ if not hasattr(source, "read"):
+ source = open(source, "rb")
+ close_source = True
+ yield None
  while True:
  yield from pullparser.read_events()
  # load event buffer
@@ -1261,16 +1267,12 @@ def iterator():
  source.close()
 
  class IterParseIterator(collections.abc.Iterator):
- __next__ = iterator().__next__
+ __next__ = iterator(source).__next__
  it = IterParseIterator()
  it.root = None
  del iterator, IterParseIterator
 
- close_source = False
- if not hasattr(source, "read"):
- source = open(source, "rb")
- close_source = True
-
+ next(it)
  return it
 
 

Misc/ACKS

@@ -1879,6 +1879,7 @@ Wojtek Walczak
 Charles Waldman
 Richard Walker
 Larry Wall
+Jacob Walls
 Kevin Walzer
 Rodrigo Steinmuller Wanderley
 Dingyuan Wang

Misc/NEWS.d/next/Library/2022-03-05-09-43-53.bpo-25707.gTlclP.rst

@@ -0,0 +1,2 @@
+Fixed a file leak in :func:`xml.etree.ElementTree.iterparse` when the
+iterator is not exhausted. Patch by Jacob Walls.