annotate rust/hg-cpython/src/ancestors.rs @ 42609:326fdce22fb2

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

// 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 the `hg::ancestors` module provided by the
//! `hg-core` crate. From Python, this will be seen as `rustext.ancestor`
//! and can be used as replacement for the the pure `ancestor` Python module.
//!
//! # Classes visible from Python:
//! - [`LazyAncestors`] is the Rust implementation of
//!   `mercurial.ancestor.lazyancestors`. The only difference is that it is
//!   instantiated with a C `parsers.index` instance instead of a parents
//!   function.
//!
//! - [`MissingAncestors`] is the Rust implementation of
//!   `mercurial.ancestor.incrementalmissingancestors`.
//!
//!   API differences:
//!    + it is instantiated with a C `parsers.index`
//!      instance instead of a parents function.
//!    + `MissingAncestors.bases` is a method returning a tuple instead of
//!      a set-valued attribute. We could return a Python set easily if our
//!      [PySet PR](https://github.com/dgrunwald/rust-cpython/pull/165)
//!      is accepted.
//!
//! - [`AncestorsIterator`] is the Rust counterpart of the
//!   `ancestor._lazyancestorsiter` Python generator. From Python, instances of
//!   this should be mainly obtained by calling `iter()` on a [`LazyAncestors`]
//!   instance.
//!
//! [`LazyAncestors`]: struct.LazyAncestors.html
//! [`MissingAncestors`]: struct.MissingAncestors.html
//! [`AncestorsIterator`]: struct.AncestorsIterator.html
use crate::{
    cindex::Index,
    conversion::{py_set, rev_pyiter_collect},
    exceptions::GraphError,
};
use cpython::{
    ObjectProtocol, PyClone, PyDict, PyList, PyModule, PyObject, PyResult,
    Python, PythonObject, ToPyObject,
};
use hg::Revision;
use hg::{
    AncestorsIterator as CoreIterator, LazyAncestors as CoreLazy,
    MissingAncestors as CoreMissing,
};
use std::cell::RefCell;
use std::collections::HashSet;

py_class!(pub class AncestorsIterator |py| {
    data inner: RefCell<Box<CoreIterator<Index>>>;

    def __next__(&self) -> PyResult<Option<Revision>> {
        match self.inner(py).borrow_mut().next() {
            Some(Err(e)) => Err(GraphError::pynew(py, e)),
            None => Ok(None),
            Some(Ok(r)) => Ok(Some(r)),
        }
    }

    def __contains__(&self, rev: Revision) -> PyResult<bool> {
        self.inner(py).borrow_mut().contains(rev)
            .map_err(|e| GraphError::pynew(py, e))
    }

    def __iter__(&self) -> PyResult<Self> {
        Ok(self.clone_ref(py))
    }

    def __new__(_cls, index: PyObject, initrevs: PyObject, stoprev: Revision,
                inclusive: bool) -> PyResult<AncestorsIterator> {
        let initvec: Vec<Revision> = rev_pyiter_collect(py, &initrevs)?;
        let ait = CoreIterator::new(
            Index::new(py, index)?,
            initvec,
            stoprev,
            inclusive,
        )
        .map_err(|e| GraphError::pynew(py, e))?;
        AncestorsIterator::from_inner(py, ait)
    }

});

impl AncestorsIterator {
    pub fn from_inner(py: Python, ait: CoreIterator<Index>) -> PyResult<Self> {
        Self::create_instance(py, RefCell::new(Box::new(ait)))
    }
}

py_class!(pub class LazyAncestors |py| {
    data inner: RefCell<Box<CoreLazy<Index>>>;

    def __contains__(&self, rev: Revision) -> PyResult<bool> {
        self.inner(py)
            .borrow_mut()
            .contains(rev)
            .map_err(|e| GraphError::pynew(py, e))
    }

    def __iter__(&self) -> PyResult<AncestorsIterator> {
        AncestorsIterator::from_inner(py, self.inner(py).borrow().iter())
    }

    def __bool__(&self) -> PyResult<bool> {
        Ok(!self.inner(py).borrow().is_empty())
    }

    def __new__(_cls, index: PyObject, initrevs: PyObject, stoprev: Revision,
                inclusive: bool) -> PyResult<Self> {
        let initvec: Vec<Revision> = rev_pyiter_collect(py, &initrevs)?;

        let lazy =
            CoreLazy::new(Index::new(py, index)?, initvec, stoprev, inclusive)
                .map_err(|e| GraphError::pynew(py, e))?;

        Self::create_instance(py, RefCell::new(Box::new(lazy)))
        }

});

py_class!(pub class MissingAncestors |py| {
    data inner: RefCell<Box<CoreMissing<Index>>>;

    def __new__(_cls, index: PyObject, bases: PyObject) -> PyResult<MissingAncestors> {
        let bases_vec: Vec<Revision> = rev_pyiter_collect(py, &bases)?;
        let inner = CoreMissing::new(Index::new(py, index)?, bases_vec);
        MissingAncestors::create_instance(py, RefCell::new(Box::new(inner)))
    }

    def hasbases(&self) -> PyResult<bool> {
        Ok(self.inner(py).borrow().has_bases())
    }

    def addbases(&self, bases: PyObject) -> PyResult<PyObject> {
        let mut inner = self.inner(py).borrow_mut();
        let bases_vec: Vec<Revision> = rev_pyiter_collect(py, &bases)?;
        inner.add_bases(bases_vec);
        // cpython doc has examples with PyResult<()> but this gives me
        //   the trait `cpython::ToPyObject` is not implemented for `()`
        // so let's return an explicit None
        Ok(py.None())
    }

    def bases(&self) -> PyResult<PyObject> {
        py_set(py, self.inner(py).borrow().get_bases())
    }

    def basesheads(&self) -> PyResult<PyObject> {
        let inner = self.inner(py).borrow();
        py_set(py, &inner.bases_heads().map_err(|e| GraphError::pynew(py, e))?)
    }

    def removeancestorsfrom(&self, revs: PyObject) -> PyResult<PyObject> {
        let mut inner = self.inner(py).borrow_mut();
        // this is very lame: we convert to a Rust set, update it in place
        // and then convert back to Python, only to have Python remove the
        // excess (thankfully, Python is happy with a list or even an iterator)
        // Leads to improve this:
        //  - have the CoreMissing instead do something emit revisions to
        //    discard
        //  - define a trait for sets of revisions in the core and implement
        //    it for a Python set rewrapped with the GIL marker
        let mut revs_pyset: HashSet<Revision> = rev_pyiter_collect(py, &revs)?;
        inner.remove_ancestors_from(&mut revs_pyset)
            .map_err(|e| GraphError::pynew(py, e))?;

        // convert as Python list
        let mut remaining_pyint_vec: Vec<PyObject> = Vec::with_capacity(
            revs_pyset.len());
        for rev in revs_pyset {
            remaining_pyint_vec.push(rev.to_py_object(py).into_object());
        }
        let remaining_pylist = PyList::new(py, remaining_pyint_vec.as_slice());
        revs.call_method(py, "intersection_update", (remaining_pylist, ), None)
    }

    def missingancestors(&self, revs: PyObject) -> PyResult<PyList> {
        let mut inner = self.inner(py).borrow_mut();
        let revs_vec: Vec<Revision> = rev_pyiter_collect(py, &revs)?;
        let missing_vec = match inner.missing_ancestors(revs_vec) {
            Ok(missing) => missing,
            Err(e) => {
                return Err(GraphError::pynew(py, e));
            }
        };
        // convert as Python list
        let mut missing_pyint_vec: Vec<PyObject> = Vec::with_capacity(
            missing_vec.len());
        for rev in missing_vec {
            missing_pyint_vec.push(rev.to_py_object(py).into_object());
        }
        Ok(PyList::new(py, missing_pyint_vec.as_slice()))
    }
});

/// Create the module, with __package__ given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.ancestor", package);
    let m = PyModule::new(py, dotted_name)?;
    m.add(py, "__package__", package)?;
    m.add(
        py,
        "__doc__",
        "Generic DAG ancestor algorithms - Rust implementation",
    )?;
    m.add_class::<AncestorsIterator>(py)?;
    m.add_class::<LazyAncestors>(py)?;
    m.add_class::<MissingAncestors>(py)?;

    let sys = PyModule::import(py, "sys")?;
    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
    sys_modules.set_item(py, dotted_name, &m)?;
    // Example C code (see pyexpat.c and import.c) will "give away the
    // reference", but we won't because it will be consumed once the
    // Rust PyObject is dropped.
    Ok(m)
}