view rust/hg-cpython/src/exceptions.rs @ 50979:4c5f6e95df84

rust: make `Revision` a newtype

This change is the one we've been building towards during this series.
The aim is to make `Revision` mean more than a simple integer, holding
the information that it is valid for a given revlog index.
While this still allows for programmer error, since creating a revision
directly and querying a different index with a "checked" revision are
still possible, the friction created by the newtype will hopefully make
us think twice about which type to use.

Enough of the Rust ecosystem relies on the newtype pattern to be
efficiently optimized away (even compiler in codegen tests¹), so I'm not
worried about this being a fundamental problem.

[1] https://github.com/rust-lang/rust/blob/7a70647f195f6b0a0f1ebd72b1542ba91a32f43a/tests/codegen/vec-in-place.rs#L47

// ancestors.rs
//
// Copyright 2018 Georges Racinet <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

//! Bindings for Rust errors
//!
//! [`GraphError`] exposes `hg::GraphError` as a subclass of `ValueError`
//! but some variants of `hg::GraphError` can be converted directly to other
//! existing Python exceptions if appropriate.
//!
//! [`GraphError`]: struct.GraphError.html
use cpython::{
    exc::{RuntimeError, ValueError},
    py_exception, PyErr, Python,
};
use hg;

use crate::PyRevision;

py_exception!(rustext, GraphError, ValueError);

impl GraphError {
    pub fn pynew(py: Python, inner: hg::GraphError) -> PyErr {
        match inner {
            hg::GraphError::ParentOutOfRange(r) => {
                GraphError::new(py, ("ParentOutOfRange", PyRevision(r.0)))
            }
        }
    }

    pub fn pynew_from_vcsgraph(
        py: Python,
        inner: vcsgraph::graph::GraphReadError,
    ) -> PyErr {
        match inner {
            vcsgraph::graph::GraphReadError::InconsistentGraphData => {
                GraphError::new(py, "InconsistentGraphData")
            }
            vcsgraph::graph::GraphReadError::InvalidKey => {
                GraphError::new(py, "ParentOutOfRange")
            }
            vcsgraph::graph::GraphReadError::KeyedInvalidKey(r) => {
                GraphError::new(py, ("ParentOutOfRange", r))
            }
            vcsgraph::graph::GraphReadError::WorkingDirectoryUnsupported => {
                match py
                    .import("mercurial.error")
                    .and_then(|m| m.get(py, "WdirUnsupported"))
                {
                    Err(e) => e,
                    Ok(cls) => PyErr::from_instance(py, cls),
                }
            }
        }
    }
}

py_exception!(rustext, HgPathPyError, RuntimeError);
py_exception!(rustext, FallbackError, RuntimeError);
py_exception!(shared_ref, AlreadyBorrowed, RuntimeError);