rust/hg-cpython/src/filepatterns.rs

rust: switch hg-core and hg-cpython to rust 2018 edition

Many interesting changes have happened in Rust since the Oxidation Plan was
introduced, like the 2018 edition and procedural macros:

    - Opting in to the 2018 edition is a clear benefit in terms of future
      proofing, new (nice to have) syntactical sugar notwithstanding. It
      also has a new non-lexical, non-AST based borrow checker that has
      fewer bugs(!) and allows us to write correct code that in some cases
      would have been rejected by the old one.
    - Procedural macros allow us to use the PyO3 crate which maintainers have
      expressed the clear goal of compiling on stable, which would help in
      code maintainability compared to rust-cpython.

In this patch are the following changes:
    - Removing most `extern crate` uses
    - Updating `use` clauses (`crate` keyword, nested `use`)
    - Removing `mod.rs` in favor of an aptly named module file

Like discussed in the mailing list (
https://www.mercurial-scm.org/pipermail/mercurial-devel/2019-July/132316.html
), until Rust integration in Mercurial is considered to be out of the
experimental phase, the maximum version of Rust allowed is whatever the latest
version Debian packages.

Differential Revision: https://phab.mercurial-scm.org/D6597

// filepatterns.rs
//
// Copyright 2019, Georges Racinet <[e-mail]>,
// Raphaël Gomès <[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::filepatterns` module provided by the
//! `hg-core` crate. From Python, this will be seen as `rustext.filepatterns`
//! and can be used as replacement for the the pure `filepatterns` Python module.
//!
use crate::exceptions::{PatternError, PatternFileError};
use cpython::{
    PyBytes, PyDict, PyModule, PyObject, PyResult, PyTuple, Python, ToPyObject,
};
use hg::{build_single_regex, read_pattern_file, LineNumber, PatternTuple};

/// Rust does not like functions with different return signatures.
/// The 3-tuple version is always returned by the hg-core function,
/// the (potential) conversion is handled at this level since it is not likely
/// to have any measurable impact on performance.
///
/// The Python implementation passes a function reference for `warn` instead
/// of a boolean that is used to emit warnings while parsing. The Rust
/// implementation chooses to accumulate the warnings and propagate them to
/// Python upon completion. See the `readpatternfile` function in `match.py`
/// for more details.
fn read_pattern_file_wrapper(
    py: Python,
    file_path: PyObject,
    warn: bool,
    source_info: bool,
) -> PyResult<PyTuple> {
    match read_pattern_file(file_path.extract::<PyBytes>(py)?.data(py), warn) {
        Ok((patterns, warnings)) => {
            if source_info {
                let itemgetter = |x: &PatternTuple| {
                    (PyBytes::new(py, &x.0), x.1, PyBytes::new(py, &x.2))
                };
                let results: Vec<(PyBytes, LineNumber, PyBytes)> =
                    patterns.iter().map(itemgetter).collect();
                return Ok((results, warnings).to_py_object(py));
            }
            let itemgetter = |x: &PatternTuple| PyBytes::new(py, &x.0);
            let results: Vec<PyBytes> =
                patterns.iter().map(itemgetter).collect();
            Ok((results, warnings).to_py_object(py))
        }
        Err(e) => Err(PatternFileError::pynew(py, e)),
    }
}

fn build_single_regex_wrapper(
    py: Python,
    kind: PyObject,
    pat: PyObject,
    globsuffix: PyObject,
) -> PyResult<PyBytes> {
    match build_single_regex(
        kind.extract::<PyBytes>(py)?.data(py),
        pat.extract::<PyBytes>(py)?.data(py),
        globsuffix.extract::<PyBytes>(py)?.data(py),
    ) {
        Ok(regex) => Ok(PyBytes::new(py, &regex)),
        Err(e) => Err(PatternError::pynew(py, e)),
    }
}

pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.filepatterns", package);
    let m = PyModule::new(py, dotted_name)?;

    m.add(py, "__package__", package)?;
    m.add(
        py,
        "__doc__",
        "Patterns files parsing - Rust implementation",
    )?;
    m.add(
        py,
        "build_single_regex",
        py_fn!(
            py,
            build_single_regex_wrapper(
                kind: PyObject,
                pat: PyObject,
                globsuffix: PyObject
            )
        ),
    )?;
    m.add(
        py,
        "read_pattern_file",
        py_fn!(
            py,
            read_pattern_file_wrapper(
                file_path: PyObject,
                warn: bool,
                source_info: bool
            )
        ),
    )?;
    m.add(py, "PatternError", py.get_type::<PatternError>())?;
    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)
}