rust/rhg/src/main.rs

rhg: add support for detailed exit code for ConfigParseError

This patch adds basic support for detailed exit code to rhg with support for
ConfigParseError.

For now, if parsing the config results in error, we silently fallbacks to
`false`. The python version in this case emits a traceback.

Differential Revision: https://phab.mercurial-scm.org/D10253

extern crate log;
use crate::ui::Ui;
use clap::App;
use clap::AppSettings;
use clap::Arg;
use clap::ArgMatches;
use format_bytes::{format_bytes, join};
use hg::config::Config;
use hg::repo::{Repo, RepoError};
use hg::utils::files::{get_bytes_from_os_str, get_path_from_bytes};
use hg::utils::SliceExt;
use std::ffi::OsString;
use std::path::PathBuf;
use std::process::Command;

mod blackbox;
mod error;
mod exitcode;
mod ui;
use error::CommandError;

fn main_with_result(
    process_start_time: &blackbox::ProcessStartTime,
    ui: &ui::Ui,
    repo: Result<&Repo, &NoRepoInCwdError>,
    config: &Config,
) -> Result<(), CommandError> {
    check_extensions(config)?;

    let app = App::new("rhg")
        .global_setting(AppSettings::AllowInvalidUtf8)
        .global_setting(AppSettings::DisableVersion)
        .setting(AppSettings::SubcommandRequired)
        .setting(AppSettings::VersionlessSubcommands)
        .arg(
            Arg::with_name("repository")
                .help("repository root directory")
                .short("-R")
                .long("--repository")
                .value_name("REPO")
                .takes_value(true)
                // Both ok: `hg -R ./foo log` or `hg log -R ./foo`
                .global(true),
        )
        .arg(
            Arg::with_name("config")
                .help("set/override config option (use 'section.name=value')")
                .long("--config")
                .value_name("CONFIG")
                .takes_value(true)
                .global(true)
                // Ok: `--config section.key1=val --config section.key2=val2`
                .multiple(true)
                // Not ok: `--config section.key1=val section.key2=val2`
                .number_of_values(1),
        )
        .arg(
            Arg::with_name("cwd")
                .help("change working directory")
                .long("--cwd")
                .value_name("DIR")
                .takes_value(true)
                .global(true),
        )
        .version("0.0.1");
    let app = add_subcommand_args(app);

    let matches = app.clone().get_matches_safe()?;

    let (subcommand_name, subcommand_matches) = matches.subcommand();
    let run = subcommand_run_fn(subcommand_name)
        .expect("unknown subcommand name from clap despite AppSettings::SubcommandRequired");
    let subcommand_args = subcommand_matches
        .expect("no subcommand arguments from clap despite AppSettings::SubcommandRequired");

    let invocation = CliInvocation {
        ui,
        subcommand_args,
        config,
        repo,
    };
    let blackbox = blackbox::Blackbox::new(&invocation, process_start_time)?;
    blackbox.log_command_start();
    let result = run(&invocation);
    blackbox.log_command_end(exit_code(
        &result,
        // TODO: show a warning or combine with original error if `get_bool`
        // returns an error
        config
            .get_bool(b"ui", b"detailed-exit-code")
            .unwrap_or(false),
    ));
    result
}

fn main() {
    // Run this first, before we find out if the blackbox extension is even
    // enabled, in order to include everything in-between in the duration
    // measurements. Reading config files can be slow if they’re on NFS.
    let process_start_time = blackbox::ProcessStartTime::now();

    env_logger::init();
    let ui = ui::Ui::new();

    let early_args = EarlyArgs::parse(std::env::args_os());

    let initial_current_dir = early_args.cwd.map(|cwd| {
        let cwd = get_path_from_bytes(&cwd);
        std::env::current_dir()
            .and_then(|initial| {
                std::env::set_current_dir(cwd)?;
                Ok(initial)
            })
            .unwrap_or_else(|error| {
                exit(
                    &None,
                    &ui,
                    OnUnsupported::Abort,
                    Err(CommandError::abort(format!(
                        "abort: {}: '{}'",
                        error,
                        cwd.display()
                    ))),
                    false,
                )
            })
    });

    let non_repo_config =
        Config::load(early_args.config).unwrap_or_else(|error| {
            // Normally this is decided based on config, but we don’t have that
            // available. As of this writing config loading never returns an
            // "unsupported" error but that is not enforced by the type system.
            let on_unsupported = OnUnsupported::Abort;

            exit(
                &initial_current_dir,
                &ui,
                on_unsupported,
                Err(error.into()),
                false,
            )
        });

    if let Some(repo_path_bytes) = &early_args.repo {
        lazy_static::lazy_static! {
            static ref SCHEME_RE: regex::bytes::Regex =
                // Same as `_matchscheme` in `mercurial/util.py`
                regex::bytes::Regex::new("^[a-zA-Z0-9+.\\-]+:").unwrap();
        }
        if SCHEME_RE.is_match(&repo_path_bytes) {
            exit(
                &initial_current_dir,
                &ui,
                OnUnsupported::from_config(&ui, &non_repo_config),
                Err(CommandError::UnsupportedFeature {
                    message: format_bytes!(
                        b"URL-like --repository {}",
                        repo_path_bytes
                    ),
                }),
                // TODO: show a warning or combine with original error if
                // `get_bool` returns an error
                non_repo_config
                    .get_bool(b"ui", b"detailed-exit-code")
                    .unwrap_or(false),
            )
        }
    }
    let repo_path = early_args.repo.as_deref().map(get_path_from_bytes);
    let repo_result = match Repo::find(&non_repo_config, repo_path) {
        Ok(repo) => Ok(repo),
        Err(RepoError::NotFound { at }) if repo_path.is_none() => {
            // Not finding a repo is not fatal yet, if `-R` was not given
            Err(NoRepoInCwdError { cwd: at })
        }
        Err(error) => exit(
            &initial_current_dir,
            &ui,
            OnUnsupported::from_config(&ui, &non_repo_config),
            Err(error.into()),
            // TODO: show a warning or combine with original error if
            // `get_bool` returns an error
            non_repo_config
                .get_bool(b"ui", b"detailed-exit-code")
                .unwrap_or(false),
        ),
    };

    let config = if let Ok(repo) = &repo_result {
        repo.config()
    } else {
        &non_repo_config
    };
    let on_unsupported = OnUnsupported::from_config(&ui, config);

    let result = main_with_result(
        &process_start_time,
        &ui,
        repo_result.as_ref(),
        config,
    );
    exit(
        &initial_current_dir,
        &ui,
        on_unsupported,
        result,
        // TODO: show a warning or combine with original error if `get_bool`
        // returns an error
        config
            .get_bool(b"ui", b"detailed-exit-code")
            .unwrap_or(false),
    )
}

fn exit_code(
    result: &Result<(), CommandError>,
    use_detailed_exit_code: bool,
) -> i32 {
    match result {
        Ok(()) => exitcode::OK,
        Err(CommandError::Abort {
            message: _,
            detailed_exit_code,
        }) => {
            if use_detailed_exit_code {
                *detailed_exit_code
            } else {
                exitcode::ABORT
            }
        }
        Err(CommandError::Unsuccessful) => exitcode::UNSUCCESSFUL,

        // Exit with a specific code and no error message to let a potential
        // wrapper script fallback to Python-based Mercurial.
        Err(CommandError::UnsupportedFeature { .. }) => {
            exitcode::UNIMPLEMENTED
        }
    }
}

fn exit(
    initial_current_dir: &Option<PathBuf>,
    ui: &Ui,
    mut on_unsupported: OnUnsupported,
    result: Result<(), CommandError>,
    use_detailed_exit_code: bool,
) -> ! {
    if let (
        OnUnsupported::Fallback { executable },
        Err(CommandError::UnsupportedFeature { .. }),
    ) = (&on_unsupported, &result)
    {
        let mut args = std::env::args_os();
        let executable_path = get_path_from_bytes(&executable);
        let this_executable = args.next().expect("exepcted argv[0] to exist");
        if executable_path == &PathBuf::from(this_executable) {
            // Avoid spawning infinitely many processes until resource
            // exhaustion.
            let _ = ui.write_stderr(&format_bytes!(
                b"Blocking recursive fallback. The 'rhg.fallback-executable = {}' config \
                points to `rhg` itself.\n",
                executable
            ));
            on_unsupported = OnUnsupported::Abort
        } else {
            // `args` is now `argv[1..]` since we’ve already consumed `argv[0]`
            let mut command = Command::new(executable_path);
            command.args(args);
            if let Some(initial) = initial_current_dir {
                command.current_dir(initial);
            }
            let result = command.status();
            match result {
                Ok(status) => std::process::exit(
                    status.code().unwrap_or(exitcode::ABORT),
                ),
                Err(error) => {
                    let _ = ui.write_stderr(&format_bytes!(
                        b"tried to fall back to a '{}' sub-process but got error {}\n",
                        executable, format_bytes::Utf8(error)
                    ));
                    on_unsupported = OnUnsupported::Abort
                }
            }
        }
    }
    exit_no_fallback(ui, on_unsupported, result, use_detailed_exit_code)
}

fn exit_no_fallback(
    ui: &Ui,
    on_unsupported: OnUnsupported,
    result: Result<(), CommandError>,
    use_detailed_exit_code: bool,
) -> ! {
    match &result {
        Ok(_) => {}
        Err(CommandError::Unsuccessful) => {}
        Err(CommandError::Abort {
            message,
            detailed_exit_code: _,
        }) => {
            if !message.is_empty() {
                // Ignore errors when writing to stderr, we’re already exiting
                // with failure code so there’s not much more we can do.
                let _ = ui.write_stderr(&format_bytes!(b"{}\n", message));
            }
        }
        Err(CommandError::UnsupportedFeature { message }) => {
            match on_unsupported {
                OnUnsupported::Abort => {
                    let _ = ui.write_stderr(&format_bytes!(
                        b"unsupported feature: {}\n",
                        message
                    ));
                }
                OnUnsupported::AbortSilent => {}
                OnUnsupported::Fallback { .. } => unreachable!(),
            }
        }
    }
    std::process::exit(exit_code(&result, use_detailed_exit_code))
}

macro_rules! subcommands {
    ($( $command: ident )+) => {
        mod commands {
            $(
                pub mod $command;
            )+
        }

        fn add_subcommand_args<'a, 'b>(app: App<'a, 'b>) -> App<'a, 'b> {
            app
            $(
                .subcommand(commands::$command::args())
            )+
        }

        pub type RunFn = fn(&CliInvocation) -> Result<(), CommandError>;

        fn subcommand_run_fn(name: &str) -> Option<RunFn> {
            match name {
                $(
                    stringify!($command) => Some(commands::$command::run),
                )+
                _ => None,
            }
        }
    };
}

subcommands! {
    cat
    debugdata
    debugrequirements
    files
    root
    config
}
pub struct CliInvocation<'a> {
    ui: &'a Ui,
    subcommand_args: &'a ArgMatches<'a>,
    config: &'a Config,
    /// References inside `Result` is a bit peculiar but allow
    /// `invocation.repo?` to work out with `&CliInvocation` since this
    /// `Result` type is `Copy`.
    repo: Result<&'a Repo, &'a NoRepoInCwdError>,
}

struct NoRepoInCwdError {
    cwd: PathBuf,
}

/// CLI arguments to be parsed "early" in order to be able to read
/// configuration before using Clap. Ideally we would also use Clap for this,
/// see <https://github.com/clap-rs/clap/discussions/2366>.
///
/// These arguments are still declared when we do use Clap later, so that Clap
/// does not return an error for their presence.
struct EarlyArgs {
    /// Values of all `--config` arguments. (Possibly none)
    config: Vec<Vec<u8>>,
    /// Value of the `-R` or `--repository` argument, if any.
    repo: Option<Vec<u8>>,
    /// Value of the `--cwd` argument, if any.
    cwd: Option<Vec<u8>>,
}

impl EarlyArgs {
    fn parse(args: impl IntoIterator<Item = OsString>) -> Self {
        let mut args = args.into_iter().map(get_bytes_from_os_str);
        let mut config = Vec::new();
        let mut repo = None;
        let mut cwd = None;
        // Use `while let` instead of `for` so that we can also call
        // `args.next()` inside the loop.
        while let Some(arg) = args.next() {
            if arg == b"--config" {
                if let Some(value) = args.next() {
                    config.push(value)
                }
            } else if let Some(value) = arg.drop_prefix(b"--config=") {
                config.push(value.to_owned())
            }

            if arg == b"--cwd" {
                if let Some(value) = args.next() {
                    cwd = Some(value)
                }
            } else if let Some(value) = arg.drop_prefix(b"--cwd=") {
                cwd = Some(value.to_owned())
            }

            if arg == b"--repository" || arg == b"-R" {
                if let Some(value) = args.next() {
                    repo = Some(value)
                }
            } else if let Some(value) = arg.drop_prefix(b"--repository=") {
                repo = Some(value.to_owned())
            } else if let Some(value) = arg.drop_prefix(b"-R") {
                repo = Some(value.to_owned())
            }
        }
        Self { config, repo, cwd }
    }
}

/// What to do when encountering some unsupported feature.
///
/// See `HgError::UnsupportedFeature` and `CommandError::UnsupportedFeature`.
enum OnUnsupported {
    /// Print an error message describing what feature is not supported,
    /// and exit with code 252.
    Abort,
    /// Silently exit with code 252.
    AbortSilent,
    /// Try running a Python implementation
    Fallback { executable: Vec<u8> },
}

impl OnUnsupported {
    const DEFAULT: Self = OnUnsupported::Abort;

    fn from_config(ui: &Ui, config: &Config) -> Self {
        match config
            .get(b"rhg", b"on-unsupported")
            .map(|value| value.to_ascii_lowercase())
            .as_deref()
        {
            Some(b"abort") => OnUnsupported::Abort,
            Some(b"abort-silent") => OnUnsupported::AbortSilent,
            Some(b"fallback") => OnUnsupported::Fallback {
                executable: config
                    .get(b"rhg", b"fallback-executable")
                    .unwrap_or_else(|| {
                        exit_no_fallback(
                            ui,
                            Self::Abort,
                            Err(CommandError::abort(
                                "abort: 'rhg.on-unsupported=fallback' without \
                                'rhg.fallback-executable' set."
                            )),
                            false,
                        )
                    })
                    .to_owned(),
            },
            None => Self::DEFAULT,
            Some(_) => {
                // TODO: warn about unknown config value
                Self::DEFAULT
            }
        }
    }
}

const SUPPORTED_EXTENSIONS: &[&[u8]] = &[b"blackbox", b"share"];

fn check_extensions(config: &Config) -> Result<(), CommandError> {
    let enabled = config.get_section_keys(b"extensions");

    let mut unsupported = enabled;
    for supported in SUPPORTED_EXTENSIONS {
        unsupported.remove(supported);
    }

    if let Some(ignored_list) =
        config.get_simple_list(b"rhg", b"ignored-extensions")
    {
        for ignored in ignored_list {
            unsupported.remove(ignored);
        }
    }

    if unsupported.is_empty() {
        Ok(())
    } else {
        Err(CommandError::UnsupportedFeature {
            message: format_bytes!(
                b"extensions: {} (consider adding them to 'rhg.ignored-extensions' config)",
                join(unsupported, b", ")
            ),
        })
    }
}