pyenum 0.0.2

Expose Rust enums to Python as real enum.Enum subclasses via PyO3.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

//! Build a Python enum class via CPython's functional API.

use pyo3::IntoPyObject;
use pyo3::prelude::*;
use pyo3::types::{PyList, PyTuple, PyType};

use crate::trait_def::{PyEnumSpec, VariantLiteral};

/// Construct the Python enum class described by `spec`.
///
/// Imports the `enum` module, calls `enum.<Base>(name, members)`, and hands
/// back an owned `Bound<PyType>`. Variant values marked as
/// [`VariantLiteral::Auto`] are passed as `enum.auto()` so CPython applies
/// its per-base defaulting rules.
pub fn build_py_enum<'py>(py: Python<'py>, spec: &PyEnumSpec) -> PyResult<Bound<'py, PyType>> {
    let enum_mod = py.import("enum")?;
    let base_cls = enum_mod.getattr(spec.base.class_name())?;
    let auto_fn = enum_mod.getattr("auto")?;

    let members = PyList::empty(py);
    for (variant_name, literal) in spec.variants {
        let value: Bound<'py, PyAny> = match literal {
            VariantLiteral::Int(v) => v.into_pyobject(py)?.into_any(),
            VariantLiteral::Str(s) => (*s).into_pyobject(py)?.into_any(),
            VariantLiteral::Auto => auto_fn.call0()?,
        };
        let name_obj: Bound<'py, PyAny> = variant_name.into_pyobject(py)?.into_any();
        let entry = PyTuple::new(py, [name_obj, value])?;
        members.append(entry)?;
    }

    let name_arg: Bound<'py, PyAny> = spec.name.into_pyobject(py)?.into_any();
    let args = PyTuple::new(py, [name_arg, members.into_any()])?;
    let class = base_cls.call1(args)?;
    class.cast_into::<PyType>().map_err(Into::into)
}