annotate rust/hg-core/src/revset.rs @ 50979:4c5f6e95df84

rust: make `Revision` a newtype

This change is the one we've been building towards during this series.
The aim is to make `Revision` mean more than a simple integer, holding
the information that it is valid for a given revlog index.
While this still allows for programmer error, since creating a revision
directly and querying a different index with a "checked" revision are
still possible, the friction created by the newtype will hopefully make
us think twice about which type to use.

Enough of the Rust ecosystem relies on the newtype pattern to be
efficiently optimized away (even compiler in codegen tests¹), so I'm not
worried about this being a fundamental problem.

[1] https://github.com/rust-lang/rust/blob/7a70647f195f6b0a0f1ebd72b1542ba91a32f43a/tests/codegen/vec-in-place.rs#L47

//! 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)
}