Support import timing and cached import diagnostics by youknowdot · Pull Request #9190 · RustPython/RustPython

youknowdot · 2026-10-18T11:13:20Z

Summary

Extract import-time diagnostics from the Python 3.15 upgrade work (#8954):

Support -X importtime / PYTHONPROFILEIMPORTTIME, including mode 2 cached-import reporting, first -X occurrence, environment override, and invalid numeric-value diagnostics.
Track nested self/cumulative timings per VM thread, with one output header per interpreter and backslash-replaced surrogate names.
Match CPython's distinct measured-import indentation and cached-import minimum encoded-byte width.
Remove only the now-obsolete CmdLineTest.test_import_time expected-failure marker through scripts/update_lib; canonical assertions and all other markers are unchanged.

This stays independent of frozen-module selection, startup initialization, and unrelated import exception changes.

Reference

CPython d220409a13b77de7a6c30abe16ea90db01528edc: Python/import.c (import_ensure_initialized and import_find_and_load_with_name) and Python/initconfig.c (config_init_import_time).

Validation

Final source 4fae3992 validated on Linux:

Locked/offline release build.
Six selected canonical tests pass: test_import_time, test_xoptions, circular import/from-import, repeated failed import, and thread creation. These are focused regression checks, not full test_cmd_line/test_import/test_thread suite passes.
Standard workspace tests (excluding wasm, venvlauncher, and CAPI) and separate cargo test from crates/capi, including doc tests.
Strict cargo clippy --all-targets -- -D warnings for the same workspace and separate CAPI scopes.
34 external option observations compared with pinned CPython: modes 0/1/2, empty/text values, sign/ASCII whitespace, overflow/trailing text, repeated options, environment precedence, -E/-I, and nested cached imports. The one known difference is documented below. All four invalid-range fatal diagnostics match exactly, as does nested cached UTF-8/surrogate output.

Normal commit hooks passed. No new Python behavioral snippets or replacement tests were added.

Known boundary

CPython's wide-character -X numeric parser inherits its startup locale. Under C.UTF-8, leading U+2003 whitespace selects mode 2 there, while this parser falls back to mode 1. Byte-based environment parsing agrees. This PR does not change process locale initialization or claim complete locale-sensitive numeric parsing parity. The existing unencodable-module-name expected-failure remains: its combined missing-module/surrogate case still reports expected failure on this independent Linux runtime, while pinned CPython passes. Cached UTF-8 and escaped-surrogate formatting matches the pinned oracle.

Assisted-by: OpenAI Codex:model version unavailable

Support -X importtime and PYTHONPROFILEIMPORTTIME, including mode 2 cached imports. Track nested timing separately in each VM thread and share the output header per interpreter. Assisted-by: OpenAI Codex:model version unavailable

Retire only test_import_time expectedFailure after the independent runtime passes its canonical assertions. Preserve other cmd-line markers and align environment range errors with CPython. Assisted-by: OpenAI Codex:model version unavailable

Keep CPython cached-import minimum width semantics for UTF-8 and backslash-replaced surrogate names. Scope the diagnostic blank line to importtime without changing CPU-count errors. Assisted-by: OpenAI Codex:model version unavailable

coderabbitai · 2026-10-18T11:13:27Z

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⛔ Files ignored due to path filters: 1

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

📒 Files selected for processing: 6

crates/vm/src/import.rs
crates/vm/src/vm/interpreter.rs
crates/vm/src/vm/mod.rs
crates/vm/src/vm/setting.rs
crates/vm/src/vm/thread.rs
src/settings.rs

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github-actions · 2026-10-18T11:18:28Z

📦 Library Dependencies

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

:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
[ ] test: cpython/Lib/test/test_cmd_line.py (TODO: 20)

dependencies:

dependent tests: (no tests depend on cmd_line)

Legend:

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

codspeed · 2026-10-18T11:42:26Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 4 skipped benchmarks¹

_{Comparing youknowdot:python315-import-timing (4fae399) with main (3f55cf4)}

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. ↩

chatgpt-codex-connector · 2026-10-18T13:38:26Z

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-18T13:45:48.592954Z	`4fae399`	Draft marked ready

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chatgpt-codex-connector · 2026-10-18T13:45:46Z

+        Some(Self {
+            state: &vm.import_timing,
+            parent,
+            start: Instant::now(),


Gate import timing's clock on wasm32-unknown-unknown

When an embedder builds rustpython_vm for wasm32-unknown-unknown and sets the new public Settings::import_time field to 1 or 2, interpreter startup reaches Instant::now() on the first uncached import; Rust's standard-library implementation panics on that target because no monotonic clock is available. This makes enabling the diagnostic abort execution instead of reporting timings, so this path needs a wasm clock implementation or a target-specific graceful fallback.

AGENTS.md reference: AGENTS.md:L11-L12

Useful? React with 👍 / 👎.

youknowdot added 3 commits October 18, 2026 19:30

Implement import timing and cached import diagnostics

6b23db7

Support -X importtime and PYTHONPROFILEIMPORTTIME, including mode 2 cached imports. Track nested timing separately in each VM thread and share the output header per interpreter. Assisted-by: OpenAI Codex:model version unavailable

Match encoded-byte padding for cached imports

4fae399

Keep CPython cached-import minimum width semantics for UTF-8 and backslash-replaced surrogate names. Scope the diagnostic blank line to importtime without changing CPU-count errors. Assisted-by: OpenAI Codex:model version unavailable

youknowone approved these changes Oct 18, 2026

View reviewed changes

youknowone marked this pull request as ready for review October 18, 2026 13:38

youknowone merged commit 6e064e5 into RustPython:main Oct 18, 2026
32 checks passed

chatgpt-codex-connector Bot reviewed Oct 18, 2026

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Support import timing and cached import diagnostics - #9190

Support import timing and cached import diagnostics#9190
youknowone merged 3 commits into
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youknowdot:python315-import-timing

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youknowdot commented Oct 18, 2026

Summary

Reference

Validation

Known boundary

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📦 Library Dependencies

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Merging this PR will not alter performance

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