annotate rust/rhg/src/commands/status.rs @ 47965:f9e6f2bb721d

rhg: Don’t compare ambiguous files one byte at a time

Even though the use of `BufReader` reduces the number of syscalls to read
the file from disk, `.bytes()` yields a separate `Result` for every byte.
Creating those results and dispatching on them is most likely costly.

Instead, this commit opts for simplicity by reading the entire file into memory
and comparing a single pair of byte strings. Note that memory already needs to
contain the entire previous contents of the file, as read from the filelog.
So with an extremely large file this doubles memory use but does not make it
grow by orders of magnitude.

At first I wrote code that still avoids reading the entire file into memory
and compares one buffer at a time with `BufReader`. Find this code below for
posterity. However its correctness is subtle. I ended up preferring the
simplicity of the obviously-correct single comparison.

```rust
let mut reader = BufReader::new(fobj);
let mut expected = &contents_in_p1[..];
loop {
    let buf = reader.fill_buf().when_reading_file(&fs_path)?;
    if buf.is_empty() {
        // Found EOF
        return Ok(expected.is_empty());
    } else if let Some(rest) = expected.drop_prefix(buf) {
        // What we read so far matches the expected content, continue reading
        let buf_len = buf.len();
        reader.consume(buf_len);
        expected = rest
    } else {
        // Found different content
        return Ok(false);
    }
}
```

Differential Revision: https://phab.mercurial-scm.org/D11412

// status.rs
//
// Copyright 2020, 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.

use crate::error::CommandError;
use crate::ui::Ui;
use clap::{Arg, SubCommand};
use hg;
use hg::dirstate_tree::dispatch::DirstateMapMethods;
use hg::errors::HgError;
use hg::manifest::Manifest;
use hg::matchers::AlwaysMatcher;
use hg::repo::Repo;
use hg::utils::hg_path::{hg_path_to_os_string, HgPath};
use hg::{HgPathCow, StatusOptions};
use log::{info, warn};

pub const HELP_TEXT: &str = "
Show changed files in the working directory

This is a pure Rust version of `hg status`.

Some options might be missing, check the list below.
";

pub fn args() -> clap::App<'static, 'static> {
    SubCommand::with_name("status")
        .alias("st")
        .about(HELP_TEXT)
        .arg(
            Arg::with_name("all")
                .help("show status of all files")
                .short("-A")
                .long("--all"),
        )
        .arg(
            Arg::with_name("modified")
                .help("show only modified files")
                .short("-m")
                .long("--modified"),
        )
        .arg(
            Arg::with_name("added")
                .help("show only added files")
                .short("-a")
                .long("--added"),
        )
        .arg(
            Arg::with_name("removed")
                .help("show only removed files")
                .short("-r")
                .long("--removed"),
        )
        .arg(
            Arg::with_name("clean")
                .help("show only clean files")
                .short("-c")
                .long("--clean"),
        )
        .arg(
            Arg::with_name("deleted")
                .help("show only deleted files")
                .short("-d")
                .long("--deleted"),
        )
        .arg(
            Arg::with_name("unknown")
                .help("show only unknown (not tracked) files")
                .short("-u")
                .long("--unknown"),
        )
        .arg(
            Arg::with_name("ignored")
                .help("show only ignored files")
                .short("-i")
                .long("--ignored"),
        )
}

/// Pure data type allowing the caller to specify file states to display
#[derive(Copy, Clone, Debug)]
pub struct DisplayStates {
    pub modified: bool,
    pub added: bool,
    pub removed: bool,
    pub clean: bool,
    pub deleted: bool,
    pub unknown: bool,
    pub ignored: bool,
}

pub const DEFAULT_DISPLAY_STATES: DisplayStates = DisplayStates {
    modified: true,
    added: true,
    removed: true,
    clean: false,
    deleted: true,
    unknown: true,
    ignored: false,
};

pub const ALL_DISPLAY_STATES: DisplayStates = DisplayStates {
    modified: true,
    added: true,
    removed: true,
    clean: true,
    deleted: true,
    unknown: true,
    ignored: true,
};

impl DisplayStates {
    pub fn is_empty(&self) -> bool {
        !(self.modified
            || self.added
            || self.removed
            || self.clean
            || self.deleted
            || self.unknown
            || self.ignored)
    }
}

pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
    let status_enabled_default = false;
    let status_enabled = invocation.config.get_option(b"rhg", b"status")?;
    if !status_enabled.unwrap_or(status_enabled_default) {
        return Err(CommandError::unsupported(
            "status is experimental in rhg (enable it with 'rhg.status = true' \
            or enable fallback with 'rhg.on-unsupported = fallback')"
        ));
    }

    let ui = invocation.ui;
    let args = invocation.subcommand_args;
    let display_states = if args.is_present("all") {
        // TODO when implementing `--quiet`: it excludes clean files
        // from `--all`
        ALL_DISPLAY_STATES
    } else {
        let requested = DisplayStates {
            modified: args.is_present("modified"),
            added: args.is_present("added"),
            removed: args.is_present("removed"),
            clean: args.is_present("clean"),
            deleted: args.is_present("deleted"),
            unknown: args.is_present("unknown"),
            ignored: args.is_present("ignored"),
        };
        if requested.is_empty() {
            DEFAULT_DISPLAY_STATES
        } else {
            requested
        }
    };

    let repo = invocation.repo?;
    let mut dmap = repo.dirstate_map_mut()?;

    let options = StatusOptions {
        // TODO should be provided by the dirstate parsing and
        // hence be stored on dmap. Using a value that assumes we aren't
        // below the time resolution granularity of the FS and the
        // dirstate.
        last_normal_time: 0,
        // we're currently supporting file systems with exec flags only
        // anyway
        check_exec: true,
        list_clean: display_states.clean,
        list_unknown: display_states.unknown,
        list_ignored: display_states.ignored,
        collect_traversed_dirs: false,
    };
    let ignore_file = repo.working_directory_vfs().join(".hgignore"); // TODO hardcoded
    let (mut ds_status, pattern_warnings) = dmap.status(
        &AlwaysMatcher,
        repo.working_directory_path().to_owned(),
        vec![ignore_file],
        options,
    )?;
    if !pattern_warnings.is_empty() {
        warn!("Pattern warnings: {:?}", &pattern_warnings);
    }

    if !ds_status.bad.is_empty() {
        warn!("Bad matches {:?}", &(ds_status.bad))
    }
    if !ds_status.unsure.is_empty() {
        info!(
            "Files to be rechecked by retrieval from filelog: {:?}",
            &ds_status.unsure
        );
    }
    if !ds_status.unsure.is_empty()
        && (display_states.modified || display_states.clean)
    {
        let p1 = repo.dirstate_parents()?.p1;
        let manifest = repo.manifest_for_node(p1).map_err(|e| {
            CommandError::from((e, &*format!("{:x}", p1.short())))
        })?;
        for to_check in ds_status.unsure {
            if cat_file_is_modified(repo, &manifest, &to_check)? {
                if display_states.modified {
                    ds_status.modified.push(to_check);
                }
            } else {
                if display_states.clean {
                    ds_status.clean.push(to_check);
                }
            }
        }
    }
    if display_states.modified {
        display_status_paths(ui, &mut ds_status.modified, b"M")?;
    }
    if display_states.added {
        display_status_paths(ui, &mut ds_status.added, b"A")?;
    }
    if display_states.removed {
        display_status_paths(ui, &mut ds_status.removed, b"R")?;
    }
    if display_states.deleted {
        display_status_paths(ui, &mut ds_status.deleted, b"!")?;
    }
    if display_states.unknown {
        display_status_paths(ui, &mut ds_status.unknown, b"?")?;
    }
    if display_states.ignored {
        display_status_paths(ui, &mut ds_status.ignored, b"I")?;
    }
    if display_states.clean {
        display_status_paths(ui, &mut ds_status.clean, b"C")?;
    }
    Ok(())
}

// Probably more elegant to use a Deref or Borrow trait rather than
// harcode HgPathBuf, but probably not really useful at this point
fn display_status_paths(
    ui: &Ui,
    paths: &mut [HgPathCow],
    status_prefix: &[u8],
) -> Result<(), CommandError> {
    paths.sort_unstable();
    for path in paths {
        // Same TODO as in commands::root
        let bytes: &[u8] = path.as_bytes();
        // TODO optim, probably lots of unneeded copies here, especially
        // if out stream is buffered
        ui.write_stdout(&[status_prefix, b" ", bytes, b"\n"].concat())?;
    }
    Ok(())
}

/// Check if a file is modified by comparing actual repo store and file system.
///
/// This meant to be used for those that the dirstate cannot resolve, due
/// to time resolution limits.
///
/// TODO: detect permission bits and similar metadata modifications
fn cat_file_is_modified(
    repo: &Repo,
    manifest: &Manifest,
    hg_path: &HgPath,
) -> Result<bool, HgError> {
    let file_node = manifest
        .find_file(hg_path)?
        .expect("ambgious file not in p1");
    let filelog = repo.filelog(hg_path)?;
    let filelog_entry = filelog.get_node(file_node).map_err(|_| {
        HgError::corrupted("filelog missing node from manifest")
    })?;
    let contents_in_p1 = filelog_entry.data()?;

    let fs_path = hg_path_to_os_string(hg_path).expect("HgPath conversion");
    let fs_contents = repo.working_directory_vfs().read(fs_path)?;
    return Ok(contents_in_p1 == &*fs_contents);
}