PYTHON-XXXX

Changes in this PR

bson.json_util.loads now rejects $timestamp value documents that contain anything other than the required t and i components. Previously, unexpected fields could be silently discarded while constructing bson.timestamp.Timestamp.

This adds regressions for both additional fields and same-length invalid key sets, and updates the changelog and contributor list.

AI assistance disclosure: I used OpenAI Codex to help investigate the existing behavior, search for duplicates, implement the change, and run validation. I reviewed and understand every changed line and can explain and maintain the contribution.

Test Plan

• python3 -m unittest test.test_json_util.TestJsonUtil.test_timestamp test.test_json_util.TestJsonUtil.test_timestamp_with_invalid_fields
• python3 -m unittest test.test_json_util test.test_bson_corpus
• ruff check bson/json_util.py test/test_json_util.py
• ruff format --check bson/json_util.py test/test_json_util.py
• python3 -m compileall -q bson/json_util.py test/test_json_util.py
• git diff --check

All listed checks passed.

Checklist

Checklist for Author

• Did you update the changelog (if necessary)?
• Is there test coverage?
• Is any followup work tracked in a JIRA ticket? If so, add links.

No follow-up work is currently identified. As an external contributor without an existing JIRA ticket, I retained the template PYTHON-XXXX placeholder for a MongoDB employee to update.

Checklist for Reviewer

• Does the title of the PR reference a JIRA Ticket?
• Do you fully understand the implementation?
• Is all relevant documentation updated?