fix(winpython): narrow search paths and add discovery cache by karthiknadig · Pull Request #456 · microsoft/python-environment-tools

karthiknadig · 2026-05-07T20:50:04Z

Fixes #453.

The WinPython locator was scanning C:\, D:\, E:\, Program Files, ~/Downloads, ~/Desktop, and ~/Documents on every refresh — all Windows Defender hot-spots — to find a niche portable distribution. That inflated p90 refresh latency for every Windows user, regardless of whether WinPython was installed.

Changes

Restrict default search to %USERPROFILE%\WinPython.
Add opt-in WINPYTHON_HOME env var (single path or ;-separated list; each entry can be or contain a WinPython install).
Add a per-process discovery cache (Arc<Mutex<Option<Arc<Vec<...>>>>>), mirroring WindowsStore and WindowsRegistry, with SyncedDiscoveryState refresh persistence.
Extract build_search_paths(userprofile, winpython_home) as a pure helper so tests don't have to mutate process env.
New regression tests pinning the search-path policy and WINPYTHON_HOME parsing on both Windows and Unix.
README: document WINPYTHON_HOME and the new search-path policy.

try_from() behavior on a real WinPython executable is unchanged — it still walks parent directories looking for marker files / WPy* directory names.

github-actions · 2026-05-07T20:50:31Z

Performance Report (Linux) ✅

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	1ms	1ms	1ms	0ms	0%
Full Refresh	55ms	436ms	64ms	-9ms	-10.0%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

Legend

🚀 Significant speedup (>100ms faster)
✅ Faster than baseline
➖ No significant change
🔺 Slower than baseline (>100ms)
⚠️ Significant slowdown (>500ms)

github-actions · 2026-05-07T20:50:33Z

Test Coverage Report (Linux)

Metric	Value
Current Coverage	76.5%
Base Branch Coverage	76.6%
Delta	-.1% ❌

Coverage decreased. Please add tests for new code.

github-actions · 2026-05-07T20:50:37Z

Performance Report (macOS)

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta
Server Startup	93ms	648ms	103ms	-10ms
Full Refresh	174ms	40351ms	175ms	-1ms

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

Legend

🚀 Significant speedup (>100ms faster)
✅ Faster than baseline
➖ No significant change
🔺 Slower than baseline (>100ms)
⚠️ Significant slowdown (>500ms)

github-actions · 2026-05-07T20:50:40Z

Performance Report (Windows) ✅

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	9ms	11ms	11ms	-2ms	-18.2%
Full Refresh	131ms	552ms	175ms	-44ms	-25.1%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

Legend

🚀 Significant speedup (>100ms faster)
✅ Faster than baseline
➖ No significant change
🔺 Slower than baseline (>100ms)
⚠️ Significant slowdown (>500ms)

github-actions · 2026-05-07T20:50:41Z

Test Coverage Report (Windows)

Metric	Value
Current Coverage	74.19%
Base Branch Coverage	73.55%
Delta	0.64% ✅

Coverage increased! Great work!

Copilot

Pull request overview

This PR addresses Windows refresh performance regressions by narrowing the WinPython locator’s default discovery scope and adding an opt-in override for custom install locations, reducing expensive filesystem scans in Windows Defender hot paths.

Changes:

Restricts default WinPython discovery to %USERPROFILE%\WinPython, removing drive-root / common-user-folder scanning.
Adds WINPYTHON_HOME (supports multiple paths) and factors path policy into a pure build_search_paths(...) helper for testability.
Introduces a WinPython discovery cache and refresh-state syncing, and adds regression tests + README documentation.

Show a summary per file

File	Description
`crates/pet-winpython/src/lib.rs`	Implements narrowed search-path policy, adds `WINPYTHON_HOME`, introduces discovery caching + refresh-state syncing, and adds tests for the new behavior.
`crates/pet-winpython/README.md`	Documents the new default search path behavior and how to opt in via `WINPYTHON_HOME`.

Copilot's findings

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Comments generated: 4

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Comments generated: 2

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…ws) (PR #456)

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Comments generated: 3

…s (PR #456)

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Files reviewed: 3/3 changed files
Comments generated: 0 new

…456) Refactor discover_environments to delegate to discover_environments_in(locator, paths) so tests can inject paths instead of mutating env vars. Add tests for parent-dir and direct-install discovery, dedup contract, missing paths, find report loop, and all sync_refresh_state_from scope variants. Skip the redundant read_dir scan when search path is itself a WinPython install.

Copilot

Copilot's findings

Files reviewed: 3/3 changed files
Comments generated: 1

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Copilot's findings

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Comments generated: 0 new

fix(winpython): narrow search paths and add discovery cache (Fixes #453)

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Comment thread crates/pet-winpython/src/lib.rs Outdated

fix: address Copilot review feedback (PR #456)

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fix: normalize all symlinks and make cache test deterministic (PR #456)

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Comment thread crates/pet-winpython/src/lib.rs Outdated

fix: normalize WINPYTHON_HOME paths in build_search_paths (PR #456)

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karthiknadig requested a review from Copilot May 7, 2026 21:20

Copilot started reviewing on behalf of karthiknadig May 7, 2026 21:21 View session

fix: gate WinPython env-var const and search-path fn behind cfg(windo…

279f03e

…ws) (PR #456)

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Comment thread crates/pet-winpython/src/lib.rs

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Comment thread crates/pet-winpython/src/lib.rs

fix: gate build_search_paths cfg and normalize expected paths in test…

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…s (PR #456)

karthiknadig requested a review from Copilot May 7, 2026 21:35

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karthiknadig marked this pull request as ready for review May 7, 2026 21:43

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Comment thread crates/pet-winpython/src/lib.rs Outdated

karthiknadig added a commit that referenced this pull request May 7, 2026

fix: gate WINPYTHON_HOME_ENV_VAR behind #[cfg(windows)] (PR #456)

44ab3ad

fix: gate WINPYTHON_HOME_ENV_VAR behind #[cfg(windows)] (PR #456)

3b40f84

karthiknadig force-pushed the feature/issue-453 branch from 44ab3ad to 3b40f84 Compare May 7, 2026 22:03

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karthiknadig enabled auto-merge (squash) May 7, 2026 22:07

roblourens approved these changes May 7, 2026

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karthiknadig merged commit 34b2d47 into main May 7, 2026
34 checks passed

karthiknadig deleted the feature/issue-453 branch May 7, 2026 22:36

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