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use crate::err::{error_on_minusone, PyResult};
use crate::types::{any::PyAnyMethods, string::PyStringMethods, PyString};
use crate::{ffi, Bound, PyAny};
/// Represents a Python traceback.
///
/// Values of this type are accessed via PyO3's smart pointers, e.g. as
/// [`Py<PyTraceback>`][crate::Py] or [`Bound<'py, PyTraceback>`][Bound].
///
/// For APIs available on traceback objects, see the [`PyTracebackMethods`] trait which is implemented for
/// [`Bound<'py, PyTraceback>`][Bound].
#[repr(transparent)]
pub struct PyTraceback(PyAny);
pyobject_native_type_core!(
PyTraceback,
pyobject_native_static_type_object!(ffi::PyTraceBack_Type),
"builtins",
"traceback",
#checkfunction=ffi::PyTraceBack_Check
);
/// Implementation of functionality for [`PyTraceback`].
///
/// These methods are defined for the `Bound<'py, PyTraceback>` smart pointer, so to use method call
/// syntax these methods are separated into a trait, because stable Rust does not yet support
/// `arbitrary_self_types`.
#[doc(alias = "PyTraceback")]
pub trait PyTracebackMethods<'py>: crate::sealed::Sealed {
/// Formats the traceback as a string.
///
/// This does not include the exception type and value. The exception type and value can be
/// formatted using the `Display` implementation for `PyErr`.
///
/// # Example
///
/// The following code formats a Python traceback and exception pair from Rust:
///
/// ```rust
/// # use pyo3::{Python, PyResult, prelude::PyTracebackMethods, ffi::c_str};
/// # let result: PyResult<()> =
/// Python::attach(|py| {
/// let err = py
/// .run(c"raise Exception('banana')", None, None)
/// .expect_err("raise will create a Python error");
///
/// let traceback = err.traceback(py).expect("raised exception will have a traceback");
/// assert_eq!(
/// format!("{}{}", traceback.format()?, err),
/// "\
/// Traceback (most recent call last):
/// File \"<string>\", line 1, in <module>
/// Exception: banana\
/// "
/// );
/// Ok(())
/// })
/// # ;
/// # result.expect("example failed");
/// ```
fn format(&self) -> PyResult<String>;
}
impl<'py> PyTracebackMethods<'py> for Bound<'py, PyTraceback> {
fn format(&self) -> PyResult<String> {
let py = self.py();
let string_io = py
.import(intern!(py, "io"))?
.getattr(intern!(py, "StringIO"))?
.call0()?;
let result = unsafe { ffi::PyTraceBack_Print(self.as_ptr(), string_io.as_ptr()) };
error_on_minusone(py, result)?;
let formatted = string_io
.getattr(intern!(py, "getvalue"))?
.call0()?
.cast::<PyString>()?
.to_cow()?
.into_owned();
Ok(formatted)
}
}
#[cfg(test)]
mod tests {
use crate::IntoPyObject;
use crate::{
types::{any::PyAnyMethods, dict::PyDictMethods, traceback::PyTracebackMethods, PyDict},
PyErr, Python,
};
#[test]
fn format_traceback() {
Python::attach(|py| {
let err = py
.run(c"raise Exception('banana')", None, None)
.expect_err("raising should have given us an error");
assert_eq!(
err.traceback(py).unwrap().format().unwrap(),
"Traceback (most recent call last):\n File \"<string>\", line 1, in <module>\n"
);
})
}
#[test]
fn test_err_from_value() {
Python::attach(|py| {
let locals = PyDict::new(py);
// Produce an error from python so that it has a traceback
py.run(
cr"
try:
raise ValueError('raised exception')
except Exception as e:
err = e
",
None,
Some(&locals),
)
.unwrap();
let err = PyErr::from_value(locals.get_item("err").unwrap().unwrap());
let traceback = err.value(py).getattr("__traceback__").unwrap();
assert!(err.traceback(py).unwrap().is(&traceback));
})
}
#[test]
fn test_err_into_py() {
Python::attach(|py| {
let locals = PyDict::new(py);
// Produce an error from python so that it has a traceback
py.run(
cr"
def f():
raise ValueError('raised exception')
",
None,
Some(&locals),
)
.unwrap();
let f = locals.get_item("f").unwrap().unwrap();
let err = f.call0().unwrap_err();
let traceback = err.traceback(py).unwrap();
let err_object = err.clone_ref(py).into_pyobject(py).unwrap();
assert!(err_object.getattr("__traceback__").unwrap().is(&traceback));
})
}
}