Generate comparison method stubs for #[pyclass(eq, ord)]

[termoshtt]

Summary

Fixes #233: Automatically generates Python stub methods for comparison operations (__eq__, __lt__, __le__, __gt__, __ge__) when PyO3 classes use the eq and ord attributes in their #[pyclass] decorator.

Problem

When using #[pyclass(eq, ord)] in PyO3, the Rust compiler automatically generates comparison methods for the class. However, pyo3-stub-gen was not generating corresponding Python stub methods, leading to missing type hints for these operations in IDEs and type checkers.

Solution

Implemented a three-phase solution that follows the existing architecture pattern:

1. Derive Phase (Metadata Collection)

• Added Eq and Ord variants to the Attr enum in pyo3-stub-gen-derive/src/gen_stub/attr.rs
• Enhanced attribute parsing to recognize eq and ord attributes in #[pyclass] decorators
• Extended PyClassInfo to include has_eq and has_ord boolean flags

2. Runtime Phase (Type Information)

• Updated runtime PyClassInfo in pyo3-stub-gen/src/type_info.rs with comparison flags
• Fixed exception macro to include the new fields with default values

3. Generation Phase (Stub Creation)

• Implemented comparison method generation in pyo3-stub-gen/src/generate/class.rs
• Added add_eq_method() to generate __eq__(self, other: object) -> bool
• Added add_ord_methods() to generate __lt__, __le__, __gt__, __ge__ methods
• Integrated into ClassDef::from to automatically add methods when flags are set

Test Coverage

Added comprehensive test coverage in examples/pure/:

• New test struct: ComparableStruct with #[pyclass(eq, ord)]
• Python tests: Verify all comparison operations work correctly
• Stub validation: Confirms proper type hints are generated

Generated Stubs

For a class like:

#[pyclass(eq, ord)]
struct ComparableStruct { ... }

The generator now produces:

class ComparableStruct:
    def __eq__(self, other: builtins.object) -> builtins.bool: ...
    def __lt__(self, other: builtins.object) -> builtins.bool: ...
    def __le__(self, other: builtins.object) -> builtins.bool: ...
    def __gt__(self, other: builtins.object) -> builtins.bool: ...
    def __ge__(self, other: builtins.object) -> builtins.bool: ...

Architecture

The implementation maintains proper separation of concerns:

• Derive side: Only collects metadata about eq/ord presence
• Generate side: Handles actual method creation and stub generation
• No breaking changes: Existing functionality remains unchanged

[Copilot]

Pull Request Overview

This PR implements automatic generation of Python stub methods for comparison operations when PyO3 classes use the eq and ord attributes in their #[pyclass] decorator, addressing issue #233.

• Adds support for detecting eq and ord attributes in #[pyclass] decorators
• Automatically generates stub methods for __eq__, __lt__, __le__, __gt__, and __ge__ operations
• Maintains architectural separation between derive-time metadata collection and generation-time stub creation

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
pyo3-stub-gen/src/type_info.rs	Adds has_eq and has_ord boolean fields to PyClassInfo struct
pyo3-stub-gen/src/lib.rs	Updates documentation example to include new comparison fields
pyo3-stub-gen/src/generate/class.rs	Implements comparison method generation logic with add_eq_method() and add_ord_methods()
pyo3-stub-gen/src/exception.rs	Updates exception macro to include default values for new fields
pyo3-stub-gen-derive/src/gen_stub/pyclass.rs	Adds parsing and processing for eq and ord attributes in derive phase
pyo3-stub-gen-derive/src/gen_stub/attr.rs	Adds Eq and Ord variants to Attr enum and parsing logic
pyo3-stub-gen-derive/src/gen_stub.rs	Updates documentation example with new fields
examples/pure/tests/test_python.py	Adds comprehensive tests for comparison operations
examples/pure/src/lib.rs	Adds ComparableStruct test class with #[pyclass(eq, ord)]
examples/pure/pure.pyi	Shows generated stub output with comparison methods

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