view rust/hg-core/src/revset.rs @ 51397:b01e7d97e167

revlog: add a Rust implementation of `headrevsdiff`

Python implementation of `headrevsdiff` can be very slow in the worst
case compared with the `heads` computation it replaces, since the
latter is done in Rust.

Even the average case of this Python implementation is still
noticeable in the profiles.

This patch makes the computation much much faster by doing it in Rust.

//! The revset query language
//!
//! <https://www.mercurial-scm.org/repo/hg/help/revsets>

use crate::errors::HgError;
use crate::repo::Repo;
use crate::revlog::NodePrefix;
use crate::revlog::{Revision, NULL_REVISION, WORKING_DIRECTORY_HEX};
use crate::revlog::{Revlog, RevlogError};
use crate::Node;

/// Resolve a query string into a single revision.
///
/// Only some of the revset language is implemented yet.
pub fn resolve_single(
    input: &str,
    repo: &Repo,
) -> Result<Revision, RevlogError> {
    let changelog = repo.changelog()?;

    match input {
        "." => {
            let p1 = repo.dirstate_parents()?.p1;
            return changelog.revlog.rev_from_node(p1.into());
        }
        "null" => return Ok(NULL_REVISION),
        _ => {}
    }

    match resolve_rev_number_or_hex_prefix(input, &changelog.revlog) {
        Err(RevlogError::InvalidRevision) => {
            // TODO: support for the rest of the language here.
            let msg = format!("cannot parse revset '{}'", input);
            Err(HgError::unsupported(msg).into())
        }
        result => result,
    }
}

/// Resolve the small subset of the language suitable for revlogs other than
/// the changelog, such as in `hg debugdata --manifest` CLI argument.
///
/// * A non-negative decimal integer for a revision number, or
/// * An hexadecimal string, for the unique node ID that starts with this
///   prefix
pub fn resolve_rev_number_or_hex_prefix(
    input: &str,
    revlog: &Revlog,
) -> Result<Revision, RevlogError> {
    // The Python equivalent of this is part of `revsymbol` in
    // `mercurial/scmutil.py`

    if let Ok(integer) = input.parse::<i32>() {
        if integer.to_string() == input
            && integer >= 0
            && revlog.has_rev(integer.into())
        {
            // This is fine because we've just checked that the revision is
            // valid for the given revlog.
            return Ok(Revision(integer));
        }
    }
    if let Ok(prefix) = NodePrefix::from_hex(input) {
        if prefix.is_prefix_of(&Node::from_hex(WORKING_DIRECTORY_HEX).unwrap())
        {
            return Err(RevlogError::WDirUnsupported);
        }
        return revlog.rev_from_node(prefix);
    }
    Err(RevlogError::InvalidRevision)
}