python / python/cpython

xml.dom.pulldom DOMEventStream drops SAX events produced by parser.close()

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stdlib topic-XML type-bug
Dominant language
Python
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Description

Bug report

Bug description:

Issue

DOMEventStream.getEvent() silently drops SAX events that are produced when parser.close() is called at end-of-stream. When the stream is exhausted, getEvent() calls self.parser.close() and immediately returns None without checking whether close() generated new events. This causes END_ELEMENT and other trailing events to be lost when bufsize causes the final tag to be split across reads.

Reproducer

import io
from xml.dom.pulldom import parse

events = list(parse(io.BytesIO(b'<a></a>'), bufsize=2))
print([e for e, _ in events])
# ['START_DOCUMENT', 'START_ELEMENT'] — END_ELEMENT is missing

Iterating the DOMEventStream (via list()) internally calls getEvent(), which is where the bug lives.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs
  • gh-145262

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with DOMEventStream.getEvent(), where the issue says parser.close() can produce events that are not checked. Run the provided BytesIO reproducer with bufsize=2 and verify that iteration retains the trailing END_ELEMENT event; linked PR gh-145262 indicates the work is already underway.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
backend
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
25/100

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