annotate rust/hg-cpython/src/conversion.rs @ 45945:50c5ee3bdf9a

copies: introduce the hg-cpython wrapper for `combine_changeset_copies`

This patch focus on the `hg-cpython` part of this work. Bridging the python code
with the new rust code in `hg-core`. The next patch will actually plug this in
the python code.

The rust code use multiple Python callback, python related error within this
callback are not expected unless they are a programming error or a data
corruption. In addition, these callback will slowly be replaced by native Rust
code. For these reasons, we use will deal with unexpected error within this
callback using rust Panic and let the `rust-cpython` layer deal with raising a
Python exception.

The code dealing with the ChangedFile instance is repeating itself a lot. I did
not factor these duplication out because that whole code will get replaced by
entirely different one in a handful of changesets.

Differential Revision: https://phab.mercurial-scm.org/D9298

// conversion.rs
//
// Copyright 2019 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 the hg::ancestors module provided by the
//! `hg-core` crate. From Python, this will be seen as `rustext.ancestor`

use cpython::{ObjectProtocol, PyObject, PyResult, Python};
use hg::Revision;
use std::iter::FromIterator;

/// Utility function to convert a Python iterable into various collections
///
/// We need this in particular to feed to various methods of inner objects
/// with `impl IntoIterator<Item=Revision>` arguments, because
/// a `PyErr` can arise at each step of iteration, whereas these methods
/// expect iterables over `Revision`, not over some `Result<Revision, PyErr>`
pub fn rev_pyiter_collect<C>(py: Python, revs: &PyObject) -> PyResult<C>
where
    C: FromIterator<Revision>,
{
    revs.iter(py)?
        .map(|r| r.and_then(|o| o.extract::<Revision>(py)))
        .collect()
}