annotate rust/hg-core/src/requirements.rs @ 46243:63c923fd7fa8

setup: when possible, build and bundle man pages

This makes it so the manual pages are built as part of the Python
build, and includes them in any wheel generated. This should make
Python wheels a much more useful and complete way of distributing
Mercurial binaries.

Differential Revision: https://phab.mercurial-scm.org/D9640

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",
];