annotate rust/hg-cpython/src/ancestors.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 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::revlog::pyindex_to_graph;
use crate::PyRevision;
use crate::{
    cindex::Index, conversion::rev_pyiter_collect, exceptions::GraphError,
};
use cpython::{
    ObjectProtocol, PyClone, PyDict, PyList, PyModule, PyObject, PyResult,
    Python, PythonObject, ToPyObject,
};
use hg::MissingAncestors as CoreMissing;
use hg::Revision;
use std::cell::RefCell;
use std::collections::HashSet;
use vcsgraph::lazy_ancestors::{
    AncestorsIterator as VCGAncestorsIterator,
    LazyAncestors as VCGLazyAncestors,
};

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

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

    def __contains__(&self, rev: PyRevision) -> PyResult<bool> {
        self.inner(py).borrow_mut().contains(rev.0)
            .map_err(|e| GraphError::pynew_from_vcsgraph(py, e))
    }

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

    def __new__(
        _cls,
        index: PyObject,
        initrevs: PyObject,
        stoprev: PyRevision,
        inclusive: bool
    ) -> PyResult<AncestorsIterator> {
        let index = pyindex_to_graph(py, index)?;
        let initvec: Vec<_> = rev_pyiter_collect(py, &initrevs, &index)?;
        let ait = VCGAncestorsIterator::new(
            index,
            initvec.into_iter().map(|r| r.0),
            stoprev.0,
            inclusive,
        )
        .map_err(|e| GraphError::pynew_from_vcsgraph(py, e))?;
        AncestorsIterator::from_inner(py, ait)
    }

});

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

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

    def __contains__(&self, rev: PyRevision) -> PyResult<bool> {
        self.inner(py)
            .borrow_mut()
            .contains(rev.0)
            .map_err(|e| GraphError::pynew_from_vcsgraph(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: PyRevision,
        inclusive: bool
    ) -> PyResult<Self> {
        let index = pyindex_to_graph(py, index)?;
        let initvec: Vec<_> = rev_pyiter_collect(py, &initrevs, &index)?;

        let lazy =
            VCGLazyAncestors::new(
                index,
                initvec.into_iter().map(|r| r.0),
                stoprev.0,
                inclusive
            )
            .map_err(|e| GraphError::pynew_from_vcsgraph(py, e))?;

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

});

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

    def __new__(
        _cls,
        index: PyObject,
        bases: PyObject
    )
    -> PyResult<MissingAncestors> {
        let index = pyindex_to_graph(py, index)?;
        let bases_vec: Vec<_> = rev_pyiter_collect(py, &bases, &index)?;

        let inner = CoreMissing::new(index.clone_ref(py), bases_vec);
        MissingAncestors::create_instance(
            py,
            RefCell::new(Box::new(inner)),
            RefCell::new(index)
        )
    }

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

    def addbases(&self, bases: PyObject) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        let bases_vec: Vec<_> = rev_pyiter_collect(py, &bases, &*index)?;
        let mut inner = self.inner(py).borrow_mut();
        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<HashSet<PyRevision>> {
        Ok(
            self.inner(py)
                .borrow()
                .get_bases()
                .iter()
                .map(|r| PyRevision(r.0))
                .collect()
        )
    }

    def basesheads(&self) -> PyResult<HashSet<PyRevision>> {
        let inner = self.inner(py).borrow();
        Ok(
            inner
                .bases_heads()
                .map_err(|e| GraphError::pynew(py, e))?
                .into_iter()
                .map(|r| PyRevision(r.0))
                .collect()
        )
    }

    def removeancestorsfrom(&self, revs: PyObject) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        // 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, &*index
        )?;
        let mut inner = self.inner(py).borrow_mut();
        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(
                PyRevision(rev.0).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 index = self.index(py).borrow();
        let revs_vec: Vec<Revision> = rev_pyiter_collect(py, &revs, &*index)?;

        let mut inner = self.inner(py).borrow_mut();
        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(
                PyRevision(rev.0).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)
}