pyo3/tests/test_exceptions.rs

use pyo3::prelude::*;
use pyo3::{exceptions, py_run, wrap_pyfunction, PyErr, PyResult};
use std::error::Error;
use std::fmt;
use std::fs::File;

mod common;

#[pyfunction]
fn fail_to_open_file() -> PyResult<()> {
    File::open("not_there.txt")?;
    Ok(())
}

#[test]
#[cfg(not(target_os = "windows"))]
fn test_filenotfounderror() {
    let gil = Python::acquire_gil();
    let py = gil.python();
    let fail_to_open_file = wrap_pyfunction!(fail_to_open_file)(py);

    py_run!(
        py,
        fail_to_open_file,
        r#"
        try:
            fail_to_open_file()
        except FileNotFoundError as e:
            assert str(e) == "No such file or directory (os error 2)"
        "#
    );
}

#[derive(Debug)]
struct CustomError;

impl Error for CustomError {}

impl fmt::Display for CustomError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Oh no!")
    }
}

impl std::convert::From<CustomError> for PyErr {
    fn from(err: CustomError) -> PyErr {
        exceptions::OSError::py_err(err.to_string())
    }
}

fn fail_with_custom_error() -> Result<(), CustomError> {
    Err(CustomError)
}

#[pyfunction]
fn call_fail_with_custom_error() -> PyResult<()> {
    fail_with_custom_error()?;
    Ok(())
}

#[test]
fn test_custom_error() {
    let gil = Python::acquire_gil();
    let py = gil.python();
    let call_fail_with_custom_error = wrap_pyfunction!(call_fail_with_custom_error)(py);

    py_run!(
        py,
        call_fail_with_custom_error,
        r#"
        try:
            call_fail_with_custom_error()
        except OSError as e:
            assert str(e) == "Oh no!"
        "#
    );
}