StatReload: exclude hidden / cache directories when scanning for .py files

[RachelXiaolan]

Summary

StatReload.iter_py_files() does a recursive rglob("*.py") and yields every match, including .py files inside .venv/, .mypy_cache/, .pytest_cache/, .ruff_cache/, and .git/. WatchFilesReload's FileFilter already excludes these (via watch_filter), but the stat-based reloader does not — so users running with watchfiles not installed see spurious reloads on venv installs, type-checker cache writes, linter cache writes, and git operations that touch .git/hooks/*.py.

Fix

Add a small static _DEFAULT_EXCLUDE_DIRS tuple to StatReload and skip any path whose parts intersect it. Mirrors the spirit of WatchFilesReload.FileFilter defaults without taking a runtime dependency on watchfiles.

Reproducer

from pathlib import Path
from uvicorn.config import Config
from uvicorn.supervisors.statreload import StatReload

root = Path("/tmp/project")
(root / "app.py").write_text("# app")
(root / ".venv" / "lib").mkdir(parents=True)
(root / ".venv" / "lib" / "somelib.py").write_text("# venv lib")
(root / ".mypy_cache").mkdir()
(root / ".mypy_cache" / "x.py").write_text("# cache")

config = Config(app="app", reload=True, reload_dirs=[str(root)])
r = StatReload(config, target=lambda **kw: None, sockets=[])
for p in r.iter_py_files():
    print(p)

Before the fix: prints app.py, .venv/lib/somelib.py, .mypy_cache/x.py — the latter two cause spurious reloads.
After the fix: prints only app.py.

Tests

tests/supervisors/test_statreload_filter.py — 2 cases:

• test_statreload_excludes_hidden_dirs — fails before, passes after
• test_statreload_includes_app_in_subdir — sanity check that real .py in a non-excluded subdir is still watched

Test run:

• New tests: 2/2 passing
• tests/supervisors/: 28 passed (full supervisors suite)
• tests/test_config.py: 122 passed
• No regressions

Refs: AI-2138 (bug-hunter Strategy B, source-code audit)

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing RachelXiaolan:ai-2138-round-2-source-audit (08967ce) with main (e8a31bc)}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}