Sandbox::https://github.com/RustPython/RustPython/pull/9005

youknowone · 2026-10-08T05:24:36Z

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Summary

Native functions now get their calling convention flags (NOARGS, O, FASTCALL, FASTCALL | KEYWORDS) from the FromArgs::PARAMS metadata of each argument. The PyMethodDef constructors compute them. Before this change, the derive macros guessed the flags from Rust type names.

This is split out of #8957. That PR rejects unsupported keywords before argument binding, which only works if KEYWORDS is accurate on every PyMethodDef. On main it is not:

list.sort(&self, options: SortOptions) is flagged O.
sorted is flagged FASTCALL without KEYWORDS.
Definitions built without the macros (the __new__ wrapper, vm.new_function, AST.__replace__) have no calling convention at all.

Details

IntoPyNativeFn::ARGS exposes the binding metadata of each argument. A &self / &Py<Self> receiver appears as the $self marker.
PyMethodFlags::with_call_convention adds the inferred calling convention unless the flags already contain one. Flags that already have one, such as C-API ml_flags, are kept as they are. With METHOD or CLASS, the first argument is the bound receiver and is not counted.
PyMethodDef::new_const, PyMethodDef::new_raw_const and Context::new_method_def apply it. Raw functions get FASTCALL | KEYWORDS.
The derive macros pass only binding flags. The string-based infer_native_call_flags is removed.

Behavior

Nothing visible from Python changes. On main, these flags are read only to pick a CALL specialization in frame.rs, and specialized calls still bind arguments through vectorcall. What changes is which specialization gets picked:

Definitions built without the macros now carry flags, so they can be specialized.
derive(FromArgs) struct arguments get accurate flags instead of being counted as one positional argument.

API: PyMethodDef::new_const takes a generic F: IntoPyNativeFn<Kind> instead of impl IntoPyNativeFn<Kind>. IntoPyNativeFn gains an associated ARGS const with a default.

Testing

cargo test --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher --exclude rustpython-capi
cargo test from crates/capi
Workspace and C-API clippy, cargo fmt --all --check
Snippets: syntax_function_args.py, builtin_type.py
Release -m test: test_extcall test_call test_builtin test_list test_ast test_descr test_int test_inspect test_datetime test_csv test_enum test_types test_functools test_dataclasses test_typing test_copy test_dict test_str test_os test_io (20 modules, all passed)

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Summary by CodeRabbit

Bug Fixes
- Native methods and module functions now use calling conventions based on their argument signatures, improving compatibility for functions with positional, keyword, optional, and variadic arguments.
- Bound methods and class methods now account for their receiver when determining how calls are handled.

`PyMethodDef::new_const`, `PyMethodDef::new_raw_const` and `Context::new_method_def` add the calling convention (`NOARGS`, `O`, `FASTCALL`, or `FASTCALL | KEYWORDS`) inferred from the `FromArgs::PARAMS` of each argument, exposed as `IntoPyNativeFn::ARGS`. Flags that already contain a calling convention, such as C-API `ml_flags`, are kept. For `METHOD` and `CLASS` the first argument is the bound receiver. Raw functions get `FASTCALL | KEYWORDS`. The derive macros pass only binding flags and no longer infer call flags from Rust type names. Definitions built without the macros, such as the `__new__` wrapper and `vm.new_function`, get calling convention flags the same way. Assisted-by: Claude Code:claude-opus-5-5

coderabbitai · 2026-10-08T05:24:54Z

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Reviewing files that changed from the base of the PR and between ca9dbb4 and 823ca0c.

📒 Files selected for processing (7)

crates/derive-impl/src/pyclass.rs
crates/derive-impl/src/pymodule.rs
crates/derive-impl/src/util.rs
crates/vm/src/function/builtin.rs
crates/vm/src/function/method.rs
crates/vm/src/function/signature.rs
crates/vm/src/vm/context.rs

💤 Files with no reviewable changes (1)

crates/derive-impl/src/util.rs

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📝 Walkthrough

Walkthrough

Native function implementations now expose argument-signature metadata. Method definitions use that metadata to infer native call-convention flags. Derive macros no longer infer these flags from Rust function signatures.

Changes

Native call conventions

Layer / File(s)	Summary
Expose native argument metadata `crates/vm/src/function/builtin.rs`	`IntoPyNativeFn` exposes `ARGS` metadata. Generated implementations describe extracted arguments and mark receiver arguments with `"$self"`.
Infer and apply call-convention flags `crates/vm/src/function/signature.rs`, `crates/vm/src/function/method.rs`, `crates/vm/src/vm/context.rs`	`native_call_flags` selects flags from argument metadata, including defaults, keyword-capable parameters, variadics, flattened parameters, and receivers. Method-definition construction applies inferred flags unless a convention is already supplied.
Remove derive-time call-flag inference `crates/derive-impl/src/pyclass.rs`, `crates/derive-impl/src/pymodule.rs`, `crates/derive-impl/src/util.rs`	Class and module derives stop inferring and storing call flags from Rust signatures. Generated definitions retain binding flags or use empty flags. The old inference utility is removed.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Suggested reviewers: leehanjeong

Merge Risk: ⚪ Minimal · up to 823ca

This change infers native call-convention flags from argument metadata instead of from Rust signatures in the derive macros. Python-visible behavior is reported to stay the same, and the author reports the test suites passing. No merge-blocking risk was found.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 47.37% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 6 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the primary change: deriving native calling-convention flags from argument metadata.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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youknowone · 2026-10-08T08:43:26Z

cc @widehyo1

youknowone merged commit bb9ef5d into RustPython:main Oct 8, 2026
21 checks passed

youknowone deleted the native-call-convention branch October 8, 2026 08:43

youknowone mentioned this pull request Oct 9, 2026

Reject unsupported native keywords before argument binding #8957

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Infer native calling convention flags from argument metadata - #9005

Infer native calling convention flags from argument metadata#9005
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