view rust/hg-core/src/requirements.rs @ 46209:a51d345f1404

upgrade: move optimization addition to determineactions()

The documentation of `determineactions()` mention that it is given a list
returned from `findoptimizations()` however it was not true before this patch.

The code extending actions with optimizations also mentioned about it that this
should be in determineactions.

So let's do what comments at couple of places say.

Differential Revision: https://phab.mercurial-scm.org/D9615

use crate::repo::Repo;
use std::io;

#[derive(Debug)]
pub enum RequirementsError {
    // TODO: include a path?
    Io(io::Error),
    /// The `requires` file is corrupted
    Corrupted,
    /// The repository requires a feature that we don't support
    Unsupported {
        feature: String,
    },
}

fn parse(bytes: &[u8]) -> Result<Vec<String>, ()> {
    // The Python code reading this file uses `str.splitlines`
    // which looks for a number of line separators (even including a couple of
    // non-ASCII ones), but Python code writing it always uses `\n`.
    let lines = bytes.split(|&byte| byte == b'\n');

    lines
        .filter(|line| !line.is_empty())
        .map(|line| {
            // Python uses Unicode `str.isalnum` but feature names are all
            // ASCII
            if line[0].is_ascii_alphanumeric() && line.is_ascii() {
                Ok(String::from_utf8(line.into()).unwrap())
            } else {
                Err(())
            }
        })
        .collect()
}

pub fn load(repo: &Repo) -> Result<Vec<String>, RequirementsError> {
    match repo.hg_vfs().read("requires") {
        Ok(bytes) => parse(&bytes).map_err(|()| RequirementsError::Corrupted),

        // Treat a missing file the same as an empty file.
        // From `mercurial/localrepo.py`:
        // > requires file contains a newline-delimited list of
        // > features/capabilities the opener (us) must have in order to use
        // > the repository. This file was introduced in Mercurial 0.9.2,
        // > which means very old repositories may not have one. We assume
        // > a missing file translates to no requirements.
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
            Ok(Vec::new())
        }

        Err(error) => Err(RequirementsError::Io(error))?,
    }
}

pub fn check(repo: &Repo) -> Result<(), RequirementsError> {
    for feature in load(repo)? {
        if !SUPPORTED.contains(&&*feature) {
            return Err(RequirementsError::Unsupported { feature });
        }
    }
    Ok(())
}

// TODO: set this to actually-supported features
const SUPPORTED: &[&str] = &[
    "dotencode",
    "fncache",
    "generaldelta",
    "revlogv1",
    "sparserevlog",
    "store",
    // As of this writing everything rhg does is read-only.
    // When it starts writing to the repository, it’ll need to either keep the
    // persistent nodemap up to date or remove this entry:
    "persistent-nodemap",
];