Improve performance of pytest discovery for large test suites#25974
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…covery by dicts to improve discovery performance for large, flat test suites
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eleanorjboyd
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Pull request overview
This PR addresses #25973 by optimizing how the vscode_pytest plugin builds the pytest discovery tree for very large suites (especially heavily-parameterized tests), reducing the pathological O(n^2) behavior caused by repeated list membership scans during tree construction.
Changes:
- Replaced per-node
childrenlists with aChildrencontainer backed by a dict keyed byid_to make repeated inserts/deduplication effectivelyO(1). - Updated tree-building code paths to use
Children.add()instead of list membership checks +append(). - Switched discovery JSON serialization to a custom encoder that also knows how to serialize
Childrencontainers back to JSON arrays (preserving the expected payload shape).
Show a summary per file
| File | Description |
|---|---|
| python_files/vscode_pytest/init.py | Reworks test-tree child storage to a dict-backed container and updates JSON encoding to keep discovery output compatible while improving performance. |
Copilot's findings
- Files reviewed: 1/1 changed files
- Comments generated: 1
Member
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Thanks for putting together this PR! Just this one comment by copilot and then I think we are good and I can approve. Appreciate it! |
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Yoyokrazy
previously approved these changes
May 29, 2026
eleanorjboyd
previously approved these changes
May 29, 2026
pwang347
approved these changes
May 29, 2026
dmitrivMS
approved these changes
May 29, 2026
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Fixes #25973
At the moment this PR demonstrates how to fix the problem, however I'll be happy to change the code however you see fit.