gh-148428: Fix file handle leak in pulldom.parse()

When pulldom.parse() is called with a filename, the opened file handle
is never closed. Add close(), context manager support, and __del__ with
ResourceWarning to DOMEventStream. Update clear() to close owned streams.

Author: WYSIATI

Doc/library/xml.dom.pulldom.rst

@@ -114,6 +114,10 @@ DOMEventStream Objects
    .. versionchanged:: 3.11
       Support for :meth:`~object.__getitem__` method has been removed.
 
+   .. versionchanged:: next
+      :class:`DOMEventStream` now supports the :term:`context manager`
+      protocol. File handles opened by :func:`parse` are closed on exit.
+
    .. method:: getEvent()
 
       Return a tuple containing *event* and the current *node* as
@@ -141,3 +145,11 @@ DOMEventStream Objects
                   print(node.toxml())
 
    .. method:: DOMEventStream.reset()
+
+   .. method:: DOMEventStream.close()
+
+      Close the underlying stream if it was opened by :func:`parse`.
+      Has no effect if the stream was provided by the caller or is already
+      closed. It is safe to call this method more than once.
+
+      .. versionadded:: next

Lib/test/test_pulldom.py

@@ -6,6 +6,7 @@
 from xml.sax.handler import feature_external_ges
 from xml.dom import pulldom
 
+from test import support
 from test.support import findfile
 
 
@@ -31,15 +32,53 @@ def test_parse(self):
         # semantics are tested using parseString with a more focused XML
         # fragment.
 
-        # Test with a filename:
-        handler = pulldom.parse(tstfile)
-        self.addCleanup(handler.stream.close)
-        list(handler)
+        # Test with a filename (context manager):
+        with pulldom.parse(tstfile) as handler:
+            list(handler)
 
         # Test with a file object:
         with open(tstfile, "rb") as fin:
             list(pulldom.parse(fin))
 
+    def test_context_manager_closes_file(self):
+        # gh-148428: context manager should close owned stream
+        with pulldom.parse(tstfile) as events:
+            stream = events.stream
+            for event, node in events:
+                pass
+        self.assertTrue(stream.closed)
+
+    def test_context_manager_does_not_close_user_stream(self):
+        # gh-148428: context manager must not close user-provided streams
+        with open(tstfile, 'rb') as f:
+            events = pulldom.DOMEventStream(f, xml.sax.make_parser(), 16384)
+            for event, node in events:
+                pass
+            events.close()
+            self.assertFalse(f.closed)
+
+    def test_close_is_idempotent(self):
+        # gh-148428: calling close() multiple times should be safe
+        events = pulldom.parse(tstfile)
+        stream = events.stream
+        events.close()
+        self.assertTrue(stream.closed)
+        events.close()  # should not raise
+
+    def test_clear_closes_owned_stream(self):
+        # gh-148428: clear() should close the stream when parse() opened it
+        events = pulldom.parse(tstfile)
+        stream = events.stream
+        events.clear()
+        self.assertTrue(stream.closed)
+
+    def test_resource_warning_on_del(self):
+        # gh-148428: unclosed DOMEventStream should emit ResourceWarning
+        events = pulldom.parse(tstfile)
+        with self.assertWarns(ResourceWarning):
+            del events
+            support.gc_collect()
+
     def test_parse_semantics(self):
         """Test DOMEventStream parsing semantics."""
 

Lib/xml/dom/pulldom.py

@@ -1,3 +1,4 @@
+import warnings
 import xml.sax
 import xml.sax.handler
 
@@ -202,10 +203,11 @@ def fatalError(self, exception):
         raise exception
 
 class DOMEventStream:
-    def __init__(self, stream, parser, bufsize):
+    def __init__(self, stream, parser, bufsize, _owns_stream=False):
         self.stream = stream
         self.parser = parser
         self.bufsize = bufsize
+        self._owns_stream = _owns_stream
         if not hasattr(self.parser, 'feed'):
             self.getEvent = self._slurp
         self.reset()
@@ -225,6 +227,28 @@ def __next__(self):
     def __iter__(self):
         return self
 
+    def close(self):
+        """Close the stream if it was opened by parse()."""
+        if self._owns_stream and self.stream is not None:
+            self.stream.close()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    def __del__(self, _warn=warnings.warn):
+        if self._owns_stream and self.stream is not None:
+            try:
+                if not self.stream.closed:
+                    _warn(
+                        f"unclosed {self!r}",
+                        ResourceWarning,
+                        source=self)
+            finally:
+                self.stream.close()
+
     def expandNode(self, node):
         event = self.getEvent()
         parents = [node]
@@ -275,6 +299,7 @@ def _emit(self):
 
     def clear(self):
         """clear(): Explicitly release parsing objects"""
+        self.close()
         self.pulldom.clear()
         del self.pulldom
         self.parser = None
@@ -320,11 +345,13 @@ def parse(stream_or_string, parser=None, bufsize=None):
         bufsize = default_bufsize
     if isinstance(stream_or_string, str):
         stream = open(stream_or_string, 'rb')
+        owns_stream = True
     else:
         stream = stream_or_string
+        owns_stream = False
     if not parser:
         parser = xml.sax.make_parser()
-    return DOMEventStream(stream, parser, bufsize)
+    return DOMEventStream(stream, parser, bufsize, _owns_stream=owns_stream)
 
 def parseString(string, parser=None):
     from io import StringIO

Misc/NEWS.d/next/Library/2026-04-12-11-14-40.gh-issue-148428.kP9qWx.rst

@@ -0,0 +1,4 @@
+:class:`xml.dom.pulldom.DOMEventStream` now supports the :term:`context
+manager` protocol and has a :meth:`~xml.dom.pulldom.DOMEventStream.close`
+method. File handles opened by :func:`xml.dom.pulldom.parse` are now
+properly closed, fixing a resource leak.