view rust/hg-core/src/operations/dirstate_status.rs @ 47093:787ff5d21bcd

dirstate-tree: Make Rust DirstateMap bindings go through a trait object

This changeset starts a series that adds an experiment to make status faster
by changing the dirstate (first only in memory and later also on disk) to
be shaped as a tree matching the directory structure, instead of the current
flat collection of entries. The status algorithm can then traverse this tree
dirstate at the same time as it traverses the filesystem.

We (Octobus) have made prototypes that show promising results but are prone
to bitrot. We would like to start upstreaming some experimental Rust code that
goes in this direction, but to avoid disrupting users it should only be
enabled by some run-time opt-in while keeping the existing dirstate structure
and status algorithm as-is.

The `DirstateMap` type and `status` function look like the appropriate
boundary. This adds a new trait that abstracts everything Python bindings need
and makes those bindings go through a `dyn` trait object. Later we’ll have two
implementations of this trait, and the same bindings can use either.

Differential Revision: https://phab.mercurial-scm.org/D10362

// 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, HgPathCow, Status};
use crate::matchers::Matcher;
use crate::{DirstateStatus, StatusError};

/// A tuple of the paths that need to be checked in the filelog because it's
/// ambiguous whether they've changed, and the rest of the already dispatched
/// files.
pub type LookupAndStatus<'a> = (Vec<HgPathCow<'a>>, DirstateStatus<'a>);

impl<'a, M: ?Sized + Matcher + Sync> Status<'a, M> {
    pub(crate) fn run(&self) -> Result<LookupAndStatus<'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().collect();

        Ok(build_response(results, traversed))
    }
}