annotate rust/hg-core/src/operations/dirstate_status.rs @ 47347:73ddcedeaadf

dirstate-tree: Change status() results to not borrow DirstateMap

The `status` function takes a `&'tree mut DirstateMap<'on_disk>` parameter.
`'on_disk` borrows a read-only byte buffer with the contents of the
`.hg/dirstate` file. `DirstateMap` internally uses represents file paths as
`std::borrow::Cow<'on_disk, HgPath>`, which borrows the byte buffer when
possible and allocates an owned string if not, such as for files added to the
dirstate after it was loaded from disk.

Previously the return type of of `status` has a `'tree` lifetime, meaning it
could borrow all paths from the `DirstateMap`. With this changeset, that
lifetime is changed to `'on_disk` meaning that only paths from the byte buffer
can be borrowed, and paths allocated by `DirstateMap` must be copied.

Usually most paths are in the byte buffer, and most paths are not part of the
return value of `status`, so the number of extra copies should be small.

This change will enable `status` to mutate the `DirstateMap` after it has
finished constructing its return value. Previously such mutation would be
prevented by possible on-going borrows.

Differential Revision: https://phab.mercurial-scm.org/D10824

// dirstate_status.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.

use crate::dirstate::status::{build_response, Dispatch, Status};
use crate::matchers::Matcher;
use crate::{DirstateStatus, StatusError};

impl<'a, M: ?Sized + Matcher + Sync> Status<'a, M> {
    pub(crate) fn run(&self) -> Result<DirstateStatus<'a>, StatusError> {
        let (traversed_sender, traversed_receiver) =
            crossbeam_channel::unbounded();

        // Step 1: check the files explicitly mentioned by the user
        let (work, mut results) = self.walk_explicit(traversed_sender.clone());

        if !work.is_empty() {
            // Hashmaps are quite a bit slower to build than vecs, so only
            // build it if needed.
            let old_results = results.iter().cloned().collect();

            // Step 2: recursively check the working directory for changes if
            // needed
            for (dir, dispatch) in work {
                match dispatch {
                    Dispatch::Directory { was_file } => {
                        if was_file {
                            results.push((dir.to_owned(), Dispatch::Removed));
                        }
                        if self.options.list_ignored
                            || self.options.list_unknown
                                && !self.dir_ignore(&dir)
                        {
                            self.traverse(
                                &dir,
                                &old_results,
                                &mut results,
                                traversed_sender.clone(),
                            );
                        }
                    }
                    _ => {
                        unreachable!("There can only be directories in `work`")
                    }
                }
            }
        }

        if !self.matcher.is_exact() {
            if self.options.list_unknown {
                self.handle_unknowns(&mut results);
            } else {
                // TODO this is incorrect, see issue6335
                // This requires a fix in both Python and Rust that can happen
                // with other pending changes to `status`.
                self.extend_from_dmap(&mut results);
            }
        }

        drop(traversed_sender);
        let traversed = traversed_receiver
            .into_iter()
            .map(std::borrow::Cow::Owned)
            .collect();

        Ok(build_response(results, traversed))
    }
}