Match startup pycache prefix and debug flag configuration by youknowdot · Pull Request #9492 · RustPython/RustPython

youknowdot · 2026-10-30T18:32:54Z

Summary

Initialize sys.pycache_prefix from PYTHONPYCACHEPREFIX or the first -X pycache_prefix option, respecting -E/-I and explicit empty or bare overrides.
Preserve filesystem path bytes through OsString and the existing native fsdecode path, without adding a codec bootstrap dependency.
Normalize the startup parser-debug flag to Boolean, matching CPython's configuration roundtrip.
Restore the canonical test_sys_flags_set and test_set_pycache_prefix methods with scripts/update_lib, retaining the other RustPython adaptations.

CPython basis

CPython 3.15.0 (d220409a13b77de7a6c30abe16ea90db01528edc):

Python/initconfig.c:config_init_pycache_prefix and Python/preconfig.c:_Py_get_xoption: first explicit option, empty/bare suppression, environment fallback.
parser_debug is a Boolean config member, normalized by config_get → _PyConfig_AsDict → getpath's _PyConfig_FromDict roundtrip.
Existing Lib/importlib/_bootstrap_external.py consumes the mutable sys.pycache_prefix attribute. No bytecode path algorithm is replaced.

Validation

Passed exact current-source Cargo check, strict Clippy, isolated CLI build, and 29 finite startup configurations against CPython (58 directly owned processes), including an undecodable Unix environment path. Every compared JSON observation matched; input fingerprints remained unchanged and all process groups terminated. Canonical subprocess methods and cross-platform coverage require CI. The no-bytecode-write local matrix uses -B, so it does not prove the empty-environment dont_write_bytecode=0 canonical case. No full startup parity claim: pre-existing generic numeric environment parsing and non-UTF8 command-line parsing limitations remain separate.

AI assistance: OpenAI Codex.

Hosted CI follow-up

The first CI run (41107874929) exposed four unexpected successes in test_compileall: test_no_args_compiles_path and test_no_args_respects_force_flag inherited by both source-epoch classes. All four passed in both the initial run and rerun on macOS, Ubuntu, and Windows. The follow-up uses scripts/update_lib to remove the two obsolete base-method decorators; test_compileall.py is now byte-identical to CPython 3.15.0. No test assertions or runtime code changed. Canonical source comparison, 228 updater tests, and normal commit hooks passed. The new commit requires fresh CI.

Restore canonical command-line configuration tests through update_lib and preserve undecodable environment paths with filesystem decoding. Assisted-by: OpenAI Codex: model version unavailable

coderabbitai · 2026-10-30T18:33:01Z

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Source mode: Auto
Repository: RustPython/RustPython
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Reviewing files that changed from the base of the PR and between a838216 and fd37a94.

Files ignored due to path filters: 1

Lib/test/test_cmd_line.py is excluded by !Lib/**

Files selected for processing: 3

crates/vm/src/stdlib/sys.rs
crates/vm/src/vm/setting.rs
src/settings.rs

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 8 remain after this review.

Walkthrough

The changes add pycache_prefix to settings, populate it from environment variables and the -X option, and expose it through sys.pycache_prefix. They also normalize the debug setting to 0 or 1.

Changes: Cache prefix configuration

Layer / File(s)	Summary
Store and populate the cache prefix `crates/vm/src/vm/setting.rs`, `src/settings.rs`	`Settings` gains an optional cache-prefix field. A nonempty environment value sets it, and the first `-X pycache_prefix` option overrides it.
Expose the cache prefix `crates/vm/src/stdlib/sys.rs`	`sys.pycache_prefix` returns the configured value as a Python string, or `None` when unset.

Debug setting normalization

Layer / File(s)	Summary
Normalize the debug setting `src/settings.rs`	The maximum of the command-line and environment debug counts is mapped to 0 or 1.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Possibly related issues

RustPython/RustPython#6839 — The changes add sys.pycache_prefix and startup handling for its environment variable and command-line option, which aligns with the issue’s pycache-prefix test objective.

Suggested reviewers: youknowone

Merge Risk: Minimal · previous review fd37a

The cache-prefix configuration preserves Windows surrogate-containing paths through the existing filesystem decoder. No merge-blocking issue was established; merge after normal checks pass.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes both main changes: startup pycache-prefix handling and debug-flag configuration.
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 1 functions across 3 files.

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github-actions · 2026-10-30T21:52:58Z

📦 Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

[ ] test: cpython/Lib/test/test_cmd_line.py (TODO: 13)

dependencies:

dependent tests: (no tests depend on cmd_line)

[x] lib: cpython/Lib/compileall.py
[x] test: cpython/Lib/test/test_compileall.py

dependencies:

compileall

dependent tests: (1 tests)

compileall: test_compileall

Legend:

[+] path exists in CPython
[x] up-to-date, [ ] outdated

chatgpt-codex-connector · 2026-10-30T23:30:04Z

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	⚠️ Failed 2026-10-30T23:30:01.591917Z We couldn’t complete this review. Comment `@codex review` to try again.	`fd37a94`	Draft marked ready

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chatgpt-codex-connector · 2026-10-30T23:30:05Z

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Remove obsolete expected failures through update_lib after initial and rerun successes on all three CI platforms. Assisted-by: OpenAI Codex: model version unavailable

codspeed · 2026-10-31T00:30:46Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 4 skipped benchmarks¹

_{Comparing youknowdot:python315-startup-config-20261030 (f83021b) with main (b7e6e58)}

4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Match startup pycache prefix and debug flag configuration

fd37a94

Restore canonical command-line configuration tests through update_lib and preserve undecodable environment paths with filesystem decoding. Assisted-by: OpenAI Codex: model version unavailable

youknowone approved these changes Oct 30, 2026

View reviewed changes

youknowone marked this pull request as ready for review October 30, 2026 23:29

Restore compileall tests passing with pycache prefix

f83021b

Remove obsolete expected failures through update_lib after initial and rerun successes on all three CI platforms. Assisted-by: OpenAI Codex: model version unavailable

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Match startup pycache prefix and debug flag configuration - #9492

Match startup pycache prefix and debug flag configuration#9492
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youknowdot:python315-startup-config-20261030

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CPython basis

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Merging this PR will not alter performance

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