annotate rust/hg-cpython/src/dirstate/dirs_multiset.rs @ 43285:ffc1fbd7d1f5

rust-cpython: make PyLeakedRef operations relatively safe

This patch encapsulates the access to the leaked reference to make most
leaked-ref operations safe. The only exception is leaked_ref.map(). I
couldn't figure out how to allow arbitrary map operation safely over an
unsafe static reference. See the docstring and inline comment for details.

Now leak_immutable() can be safely implemented as the PyLeakedRef owns
its inner data.

// dirs_multiset.rs
//
// Copyright 2019 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::dirstate::dirs_multiset` file provided by the
//! `hg-core` package.

use std::cell::RefCell;
use std::convert::TryInto;

use cpython::{
    exc, ObjectProtocol, PyBytes, PyClone, PyDict, PyErr, PyObject, PyResult,
    Python,
};

use crate::dirstate::extract_dirstate;
use crate::ref_sharing::{PyLeakedRef, PySharedRefCell};
use hg::{
    utils::hg_path::{HgPath, HgPathBuf},
    DirsMultiset, DirsMultisetIter, DirstateMapError, DirstateParseError,
    EntryState,
};

py_class!(pub class Dirs |py| {
    data inner: PySharedRefCell<DirsMultiset>;

    // `map` is either a `dict` or a flat iterator (usually a `set`, sometimes
    // a `list`)
    def __new__(
        _cls,
        map: PyObject,
        skip: Option<PyObject> = None
    ) -> PyResult<Self> {
        let mut skip_state: Option<EntryState> = None;
        if let Some(skip) = skip {
            skip_state = Some(
                skip.extract::<PyBytes>(py)?.data(py)[0]
                    .try_into()
                    .map_err(|e: DirstateParseError| {
                        PyErr::new::<exc::ValueError, _>(py, e.to_string())
                    })?,
            );
        }
        let inner = if let Ok(map) = map.cast_as::<PyDict>(py) {
            let dirstate = extract_dirstate(py, &map)?;
            DirsMultiset::from_dirstate(&dirstate, skip_state)
        } else {
            let map: Result<Vec<HgPathBuf>, PyErr> = map
                .iter(py)?
                .map(|o| {
                    Ok(HgPathBuf::from_bytes(
                        o?.extract::<PyBytes>(py)?.data(py),
                    ))
                })
                .collect();
            DirsMultiset::from_manifest(&map?)
        };

        Self::create_instance(
            py,
            PySharedRefCell::new(inner),
        )
    }

    def addpath(&self, path: PyObject) -> PyResult<PyObject> {
        self.inner_shared(py).borrow_mut()?.add_path(
            HgPath::new(path.extract::<PyBytes>(py)?.data(py)),
        );
        Ok(py.None())
    }

    def delpath(&self, path: PyObject) -> PyResult<PyObject> {
        self.inner_shared(py).borrow_mut()?.delete_path(
            HgPath::new(path.extract::<PyBytes>(py)?.data(py)),
        )
            .and(Ok(py.None()))
            .or_else(|e| {
                match e {
                    DirstateMapError::PathNotFound(_p) => {
                        Err(PyErr::new::<exc::ValueError, _>(
                            py,
                            "expected a value, found none".to_string(),
                        ))
                    }
                    DirstateMapError::EmptyPath => {
                        Ok(py.None())
                    }
                }
            })
    }
    def __iter__(&self) -> PyResult<DirsMultisetKeysIterator> {
        let leaked_ref = self.inner_shared(py).leak_immutable()?;
        DirsMultisetKeysIterator::from_inner(
            py,
            unsafe { leaked_ref.map(py, |o| o.iter()) },
        )
    }

    def __contains__(&self, item: PyObject) -> PyResult<bool> {
        Ok(self.inner(py).borrow().contains(HgPath::new(
            item.extract::<PyBytes>(py)?.data(py).as_ref(),
        )))
    }
});

py_shared_ref!(Dirs, DirsMultiset, inner, inner_shared);

impl Dirs {
    pub fn from_inner(py: Python, d: DirsMultiset) -> PyResult<Self> {
        Self::create_instance(py, PySharedRefCell::new(d))
    }

    fn translate_key(
        py: Python,
        res: &HgPathBuf,
    ) -> PyResult<Option<PyBytes>> {
        Ok(Some(PyBytes::new(py, res.as_ref())))
    }
}

py_shared_iterator!(
    DirsMultisetKeysIterator,
    PyLeakedRef<DirsMultisetIter<'static>>,
    Dirs::translate_key,
    Option<PyBytes>
);