Implement maybe_pyc_file and .pyc file execution by youknowone · Pull Request #6539 · RustPython/RustPython

youknowone

📝 Walkthrough

Walkthrough

Adds CPython-aligned .pyc magic constants, detects and executes .pyc files via a sourceless loader in the compiler path, removes dynamic git-derived MAGIC_NUMBER setup in import initialization, and exposes the pyc magic token to Python via the _imp module attribute.

Changes

Cohort / File(s)	Summary
PYC magic constants `crates/vm/src/version.rs`	Added public constants: `PYC_MAGIC_NUMBER: u16`, `PYC_MAGIC_NUMBER_TOKEN: u32`, and `PYC_MAGIC_NUMBER_BYTES: [u8;4]`.
Pyc detection & execution `crates/vm/src/vm/compile.rs`	Added `maybe_pyc_file` (and `maybe_pyc_file_with_magic`) to detect .pyc by extension/magic; branched execution to use `SourcelessFileLoader` for .pyc and `SourceFileLoader` for source; updated `set_main_loader` to accept `loader_name`.
Import init cleanup `crates/vm/src/import.rs`	Removed code that computed/assigned a dynamic 4-byte MAGIC_NUMBER from the git revision and the `get_git_revision` import; zipimport initialization unchanged.
Expose magic to Python `crates/vm/src/stdlib/imp.rs`	Added `pyc_magic_number_token` attribute to the `_imp` module, sourced from `version::PYC_MAGIC_NUMBER_TOKEN`.

Sequence Diagram(s)

sequenceDiagram
    autonumber
    participant CLI as RustPython CLI
    participant Detector as Pyc Detector (compile.rs)
    participant Loader as Import Loader (Sourceless/SourceFileLoader)
    participant VM as VirtualMachine

    CLI->>Detector: execute_file(path)
    Detector->>Detector: check extension and PYC magic
    alt .pyc detected
        Detector->>Loader: set_main_loader(..., "SourcelessFileLoader")
        Loader->>VM: get_code(module_name="__main__")
        VM->>VM: execute PyCode (bytecode)
    else source file
        Detector->>Loader: set_main_loader(..., "SourceFileLoader")
        Loader->>Loader: read source -> compile to PyCode
        Loader->>VM: run compiled PyCode
    end
    VM-->>CLI: execution result

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐇
I sniffed the bytes and found the cue,
Magic stamped in four-byte blue,
Sourceless hops — the bytecode runs,
A rabbit's cheer for faster fun! 🥕

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 77.78% which is insufficient. The required threshold is 80.00%.	You can run `@coderabbitai generate docstrings` to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly summarizes the main change: implementing maybe_pyc_file function and enabling .pyc file execution, which directly matches the file-level changes in compile.rs and the PR objectives.
Linked Issues check	✅ Passed	All coding requirements from issue #6273 are met: the PR detects .pyc files via maybe_pyc_file, handles .pyc execution with SourcelessFileLoader, and executes compiled code appropriately.
Out of Scope Changes check	✅ Passed	All changes are scoped to .pyc file support: version.rs adds magic number constants, compile.rs implements detection and execution, import.rs removes dynamic magic number setup, and imp.rs exposes the constant to Python.

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

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

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