implement sys.implementation cache_tag

[youknowone]

fix #6254

Summary by CodeRabbit

• Refactor
  • Updated system namespace implementation to compute values dynamically instead of using static literals.

[coderabbitai]

Walkthrough

The sys::implementation function now dynamically computes the cache_tag field by combining a constant implementation name with the major and minor version numbers, instead of using a hardcoded string literal. Other namespace fields remain unchanged.

Changes

Cohort / File(s)	Summary
sys::implementation cache_tag computation vm/src/stdlib/sys.rs	Replaced hardcoded cache_tag value with dynamic computation using {NAME}-{MAJOR}{MINOR} format; name field now references a NAME constant instead of a literal string

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

• Single file modification with straightforward logic replacement
• String formatting using existing version constants
• No architectural or control-flow changes

Poem

🐰 A cache tag once frozen in time,
"01" it was, oh what a crime!
Now swift like a hare, it bounds,
With versions that match—313 sounds!
Dynamic at last, the rabbit declares with delight! 🥕

Pre-merge checks and finishing touches

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'implement sys.implementation cache_tag' clearly and specifically summarizes the main change: implementing the cache_tag field in sys.implementation.
Linked Issues check	✅ Passed	The PR fixes issue #6254 by replacing the hardcoded 'rustpython-01' cache_tag with dynamic computation using version::MAJOR and version::MINOR ('{NAME}-MAJORMINOR'), which now correctly returns 'rustpython-313'.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the cache_tag issue: only sys::implementation was modified to compute cache_tag dynamically. No extraneous alterations or unrelated changes detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 9ce8586 and fb8d399.

📒 Files selected for processing (1)

• vm/src/stdlib/sys.rs (1 hunks)

🧰 Additional context used

🧠 Learnings (2)

📚 Learning: 2025-06-27T14:47:28.810Z

Learnt from: moreal
Repo: RustPython/RustPython PR: 5847
File: vm/src/stdlib/stat.rs:547-567
Timestamp: 2025-06-27T14:47:28.810Z
Learning: In RustPython's stat module implementation, platform-specific constants like SF_SUPPORTED and SF_SYNTHETIC should be conditionally declared only for the platforms where they're available (e.g., macOS), following CPython's approach of optional declaration using #ifdef checks rather than providing fallback values for other platforms.

Applied to files:

• vm/src/stdlib/sys.rs

📚 Learning: 2025-06-27T14:47:28.810Z

Learnt from: moreal
Repo: RustPython/RustPython PR: 5847
File: vm/src/stdlib/stat.rs:547-567
Timestamp: 2025-06-27T14:47:28.810Z
Learning: In RustPython's stat module implementation, platform-specific constants like SF_SUPPORTED and SF_SYNTHETIC should be conditionally declared only for the platforms where they're available (e.g., macOS), following CPython's approach of optional declaration rather than providing fallback values for other platforms.

Applied to files:

• vm/src/stdlib/sys.rs

🧬 Code graph analysis (1)

vm/src/stdlib/sys.rs (1)

vm/src/vm/context.rs (1)

• new_str (421-423)

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🔇 Additional comments (2)

vm/src/stdlib/sys.rs (2)

237-238: Consistent use of the new NAME constant and computed cache_tag.

The namespace correctly uses the NAME constant and dynamically computed cache_tag, ensuring consistency throughout the implementation.

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232-234: Good fix for the cache_tag computation.

The dynamic cache_tag computation correctly addresses the issue. The format produces "rustpython-313" matching PEP 3147 specifications. Verification confirms version::MAJOR and version::MINOR are correctly set to 3 and 13 respectively.

Since implementation() is decorated with #[pyattr], it's invoked once during module initialization and the result is cached as an attribute. The suggested Lazy<String> optimization is valid but has minimal practical impact given the single initialization call. The fix is correct as-is.

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