view rust/hg-cpython/src/utils.rs @ 49487:e8481625c582

rust: add Debug constraint to Matcher trait

This makes sure we can easily debug which Matcher we're looking at when using
trait objects, and is just generally useful. Effort to make the debugging
output nicer has been kept to a minimum, please feel free to improve.

use cpython::exc::ValueError;
use cpython::{PyBytes, PyDict, PyErr, PyObject, PyResult, PyTuple, Python};
use hg::revlog::Node;
use std::convert::TryFrom;

#[allow(unused)]
pub fn print_python_trace(py: Python) -> PyResult<PyObject> {
    eprintln!("===============================");
    eprintln!("Printing Python stack from Rust");
    eprintln!("===============================");
    let traceback = py.import("traceback")?;
    let sys = py.import("sys")?;
    let kwargs = PyDict::new(py);
    kwargs.set_item(py, "file", sys.get(py, "stderr")?)?;
    traceback.call(py, "print_stack", PyTuple::new(py, &[]), Some(&kwargs))
}

// Necessary evil for the time being, could maybe be moved to
// a TryFrom in Node itself
const NODE_BYTES_LENGTH: usize = 20;
type NodeData = [u8; NODE_BYTES_LENGTH];

/// Copy incoming Python bytes given as `PyObject` into `Node`,
/// doing the necessary checks
pub fn node_from_py_object<'a>(
    py: Python,
    bytes: &'a PyObject,
) -> PyResult<Node> {
    let as_py_bytes: &'a PyBytes = bytes.extract(py)?;
    node_from_py_bytes(py, as_py_bytes)
}

/// Clone incoming Python bytes given as `PyBytes` as a `Node`,
/// doing the necessary checks.
pub fn node_from_py_bytes(py: Python, bytes: &PyBytes) -> PyResult<Node> {
    <NodeData>::try_from(bytes.data(py))
        .map_err(|_| {
            PyErr::new::<ValueError, _>(
                py,
                format!("{}-byte hash required", NODE_BYTES_LENGTH),
            )
        })
        .map(Into::into)
}