rust/hg-cpython/src/copy_tracing.rs

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

use cpython::ObjectProtocol;
use cpython::PyBool;
use cpython::PyBytes;
use cpython::PyDict;
use cpython::PyList;
use cpython::PyModule;
use cpython::PyObject;
use cpython::PyResult;
use cpython::PyTuple;
use cpython::Python;

use hg::copy_tracing::combine_changeset_copies;
use hg::copy_tracing::ChangedFiles;
use hg::copy_tracing::RevInfo;
use hg::utils::hg_path::HgPathBuf;
use hg::Revision;

/// Combines copies information contained into revision `revs` to build a copy
/// map.
///
/// See mercurial/copies.py for details
pub fn combine_changeset_copies_wrapper(
    py: Python,
    revs: PyList,
    children: PyDict,
    target_rev: Revision,
    rev_info: PyObject,
    is_ancestor: PyObject,
) -> PyResult<PyDict> {
    let revs: PyResult<_> =
        revs.iter(py).map(|r| Ok(r.extract(py)?)).collect();

    // Wrap the `is_ancestor` python callback as a Rust closure
    //
    // No errors are expected from the Python side, and they will should only
    // happens in case of programing error or severe data corruption. Such
    // errors will raise panic and the rust-cpython harness will turn them into
    // Python exception.
    let is_ancestor_wrap = |anc: Revision, desc: Revision| -> bool {
        is_ancestor
            .call(py, (anc, desc), None)
            .expect(
                "rust-copy-tracing: python call  to `is_ancestor` \
                failed",
            )
            .cast_into::<PyBool>(py)
            .expect(
                "rust-copy-tracing: python call  to `is_ancestor` \
                returned unexpected non-Bool value",
            )
            .is_true()
    };

    // Wrap the `rev_info_maker` python callback as a Rust closure
    //
    // No errors are expected from the Python side, and they will should only
    // happens in case of programing error or severe data corruption. Such
    // errors will raise panic and the rust-cpython harness will turn them into
    // Python exception.
    let rev_info_maker = |rev: Revision| -> RevInfo {
        let res: PyTuple = rev_info
            .call(py, (rev,), None)
            .expect("rust-copy-tracing: python call to `rev_info` failed")
            .cast_into(py)
            .expect(
                "rust-copy_tracing: python call to `rev_info` returned \
                unexpected non-Tuple value",
            );
        let p1 = res.get_item(py, 0).extract(py).expect(
            "rust-copy-tracing: \
            rev_info return is invalid, first item is a not a revision",
        );
        let p2 = res.get_item(py, 1).extract(py).expect(
            "rust-copy-tracing: \
            rev_info return is invalid, second item is a not a revision",
        );

        let changes = res.get_item(py, 2);

        let files;
        if !changes
            .hasattr(py, "copied_from_p1")
            .expect("rust-copy-tracing: python call to `hasattr` failed")
        {
            files = ChangedFiles::new_empty();
        } else {
            let p1_copies: PyDict = changes
                .getattr(py, "copied_from_p1")
                .expect(
                    "rust-copy-tracing: retrieval of python attribute \
                    `copied_from_p1` failed",
                )
                .cast_into(py)
                .expect(
                    "rust-copy-tracing: failed to convert `copied_from_p1` \
                    to PyDict",
                );
            let p1_copies: PyResult<_> = p1_copies
                .items(py)
                .iter()
                .map(|(key, value)| {
                    let key = key.extract::<PyBytes>(py).expect(
                        "rust-copy-tracing: conversion of copy destination to\
                        PyBytes failed",
                    );
                    let key = key.data(py);
                    let value = value.extract::<PyBytes>(py).expect(
                        "rust-copy-tracing: conversion of copy source to \
                        PyBytes failed",
                    );
                    let value = value.data(py);
                    Ok((
                        HgPathBuf::from_bytes(key),
                        HgPathBuf::from_bytes(value),
                    ))
                })
                .collect();

            let p2_copies: PyDict = changes
                .getattr(py, "copied_from_p2")
                .expect(
                    "rust-copy-tracing: retrieval of python attribute \
                    `copied_from_p2` failed",
                )
                .cast_into(py)
                .expect(
                    "rust-copy-tracing: failed to convert `copied_from_p2` \
                    to PyDict",
                );
            let p2_copies: PyResult<_> = p2_copies
                .items(py)
                .iter()
                .map(|(key, value)| {
                    let key = key.extract::<PyBytes>(py).expect(
                        "rust-copy-tracing: conversion of copy destination to \
                        PyBytes failed");
                    let key = key.data(py);
                    let value = value.extract::<PyBytes>(py).expect(
                        "rust-copy-tracing: conversion of copy source to \
                        PyBytes failed",
                    );
                    let value = value.data(py);
                    Ok((
                        HgPathBuf::from_bytes(key),
                        HgPathBuf::from_bytes(value),
                    ))
                })
                .collect();

            let removed: PyObject = changes.getattr(py, "removed").expect(
                "rust-copy-tracing: retrieval of python attribute \
                    `removed` failed",
            );
            let removed: PyResult<_> = removed
                .iter(py)
                .expect(
                    "rust-copy-tracing: getting a python iterator over the \
                    `removed` set failed",
                )
                .map(|filename| {
                    let filename = filename
                        .expect(
                            "rust-copy-tracing: python iteration over the \
                            `removed` set failed",
                        )
                        .extract::<PyBytes>(py)
                        .expect(
                            "rust-copy-tracing: \
                            conversion of `removed` item to PyBytes failed",
                        );
                    let filename = filename.data(py);
                    Ok(HgPathBuf::from_bytes(filename))
                })
                .collect();

            let merged: PyObject = changes.getattr(py, "merged").expect(
                "rust-copy-tracing: retrieval of python attribute \
                    `merged` failed",
            );
            let merged: PyResult<_> = merged
                .iter(py)
                .expect(
                    "rust-copy-tracing: getting a python iterator over the \
                    `merged` set failed",
                )
                .map(|filename| {
                    let filename = filename
                        .expect(
                            "rust-copy-tracing: python iteration over the \
                            `merged` set failed",
                        )
                        .extract::<PyBytes>(py)
                        .expect(
                            "rust-copy-tracing: \
                            conversion of `merged` item to PyBytes failed",
                        );
                    let filename = filename.data(py);
                    Ok(HgPathBuf::from_bytes(filename))
                })
                .collect();

            let salvaged: PyObject = changes.getattr(py, "salvaged").expect(
                "rust-copy-tracing: retrieval of python attribute \
                    `salvaged` failed",
            );
            let salvaged: PyResult<_> = salvaged
                .iter(py)
                .expect(
                    "rust-copy-tracing: getting a python iterator over the \
                    `salvaged` set failed",
                )
                .map(|filename| {
                    let filename = filename
                        .expect(
                            "rust-copy-tracing: python iteration over the \
                            `salvaged` set failed",
                        )
                        .extract::<PyBytes>(py)
                        .expect(
                            "rust-copy-tracing: \
                            conversion of `salvaged` item to PyBytes failed",
                        );
                    let filename = filename.data(py);
                    Ok(HgPathBuf::from_bytes(filename))
                })
                .collect();
            files = ChangedFiles::new(
                removed.unwrap(),
                merged.unwrap(),
                salvaged.unwrap(),
                p1_copies.unwrap(),
                p2_copies.unwrap(),
            );
        }

        (p1, p2, files)
    };
    let children: PyResult<_> = children
        .items(py)
        .iter()
        .map(|(k, v)| {
            let v: &PyList = v.cast_as(py)?;
            let v: PyResult<_> =
                v.iter(py).map(|child| Ok(child.extract(py)?)).collect();
            Ok((k.extract(py)?, v?))
        })
        .collect();

    let res = combine_changeset_copies(
        revs?,
        children?,
        target_rev,
        &rev_info_maker,
        &is_ancestor_wrap,
    );
    let out = PyDict::new(py);
    for (dest, source) in res.into_iter() {
        out.set_item(
            py,
            PyBytes::new(py, &dest.into_vec()),
            PyBytes::new(py, &source.into_vec()),
        )?;
    }
    Ok(out)
}

/// Create the module, with `__package__` given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.copy_tracing", package);
    let m = PyModule::new(py, dotted_name)?;

    m.add(py, "__package__", package)?;
    m.add(py, "__doc__", "Copy tracing - Rust implementation")?;

    m.add(
        py,
        "combine_changeset_copies",
        py_fn!(
            py,
            combine_changeset_copies_wrapper(
                revs: PyList,
                children: PyDict,
                target_rev: Revision,
                rev_info: PyObject,
                is_ancestor: PyObject
            )
        ),
    )?;

    let sys = PyModule::import(py, "sys")?;
    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
    sys_modules.set_item(py, dotted_name, &m)?;

    Ok(m)
}