yash-semantics 0.15.0

// This file is part of yash, an extended POSIX shell.
// Copyright (C) 2021 WATANABE Yuki
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

//! Implementation of the and-or list semantics.

use super::Command;
use crate::Runtime;
use std::ops::ControlFlow::Continue;
use yash_env::Env;
use yash_env::semantics::Result;
use yash_env::stack::Frame;
use yash_syntax::syntax::AndOr::{self, AndThen, OrElse};
use yash_syntax::syntax::AndOrList;
use yash_syntax::syntax::Pipeline;

/// Executes the and-or list.
///
/// The `&&` operator first executes the left-hand-side pipeline, and if and
/// only if the exit status is zero, executes the right-hand-side. The `||`
/// operator works similarly but runs the right-hand-side if and only if the
/// left-hand-side exit status is non-zero. The `&&` and `||` operators are
/// left-associative and have equal precedence.
///
/// The exit status of the and-or list will be that of the last executed
/// pipeline.
///
/// [`Frame::Condition`] is pushed to the environment's stack while the
/// execution of the pipelines except for the last.
impl<S: Runtime + 'static> Command<S> for AndOrList {
    async fn execute(&self, env: &mut Env<S>) -> Result {
        if self.rest.is_empty() {
            return self.first.execute(env).await;
        }

        // Execute `first`
        let mut env2 = env.push_frame(Frame::Condition);
        self.first.execute(&mut env2).await?;

        // Execute `rest` but last
        let mut i = self.rest.iter().peekable();
        let mut pipeline;
        loop {
            pipeline = i.next().unwrap();
            if i.peek().is_none() {
                break;
            }
            execute_conditional_pipeline(&mut env2, pipeline).await?;
        }
        drop(env2);

        // Execute last
        execute_conditional_pipeline(env, pipeline).await
    }
}

async fn execute_conditional_pipeline<S: Runtime + 'static>(
    env: &mut Env<S>,
    (and_or, pipeline): &(AndOr, Pipeline),
) -> Result {
    let success = env.exit_status.is_successful();
    let run = match and_or {
        AndThen => success,
        OrElse => !success,
    };
    if run {
        pipeline.execute(env).await
    } else {
        Continue(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::tests::echo_builtin;
    use crate::tests::return_builtin;
    use assert_matches::assert_matches;
    use futures_util::FutureExt;
    use std::ops::ControlFlow::Break;
    use std::pin::Pin;
    use std::rc::Rc;
    use yash_env::VirtualSystem;
    use yash_env::builtin::Builtin;
    use yash_env::builtin::Type::Special;
    use yash_env::semantics::Divert;
    use yash_env::semantics::ExitStatus;
    use yash_env::semantics::Field;
    use yash_env::test_helper::assert_stdout;

    #[test]
    fn single_pipeline_list() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 36".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(36));
    }

    #[test]
    fn true_and_true() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        let list: AndOrList = "echo one && echo two".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus::SUCCESS);
        assert_stdout(&state, |stdout| assert_eq!(stdout, "one\ntwo\n"));
    }

    #[test]
    fn true_and_false() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 0 && return -n 5".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(5));
    }

    #[test]
    fn false_and_true() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 1 && echo !".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(1));
        assert_stdout(&state, |stdout| assert_eq!(stdout, ""));
    }

    #[test]
    fn true_and_true_and_true() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        let list: AndOrList = "echo 1 && echo 2 && echo 3".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus::SUCCESS);
        assert_stdout(&state, |stdout| assert_eq!(stdout, "1\n2\n3\n"));
    }

    #[test]
    fn true_and_false_and_true() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 0 && return -n 2 && echo !".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(2));
        assert_stdout(&state, |stdout| assert_eq!(stdout, ""));
    }

    #[test]
    fn false_and_any_or_true() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 8 && X || return -n 0".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(0));
    }

    #[test]
    fn true_or_false() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "echo + || return -n 100".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus::SUCCESS);
        assert_stdout(&state, |stdout| assert_eq!(stdout, "+\n"));
    }

    #[test]
    fn false_or_true() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "{ echo one; return -n 1; } || { echo two; }"
            .parse()
            .unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus::SUCCESS);
        assert_stdout(&state, |stdout| assert_eq!(stdout, "one\ntwo\n"));
    }

    #[test]
    fn false_or_false() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "{ echo one; return -n 1; } || { echo two; return -n 2; }"
            .parse()
            .unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(2));
        assert_stdout(&state, |stdout| assert_eq!(stdout, "one\ntwo\n"));
    }

    #[test]
    fn false_or_false_or_false() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 1 || return -n 2 || return -n 3".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(3));
    }

    #[test]
    fn false_or_true_or_false() {
        let system = VirtualSystem::new();
        let state = Rc::clone(&system.state);
        let mut env = Env::with_system(system);
        env.builtins.insert("echo", echo_builtin());
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 3 || echo + || return -n 4".parse().unwrap();

        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus::SUCCESS);
        assert_stdout(&state, |stdout| assert_eq!(stdout, "+\n"));
    }

    #[test]
    fn true_or_any_and_false() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 0 || X && return -n 9".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
        assert_eq!(env.exit_status, ExitStatus(9));
    }

    #[test]
    fn diverting_first() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        env.exit_status = ExitStatus(77);
        let list: AndOrList = "return 97".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Break(Divert::Return(Some(ExitStatus(97)))));
        assert_eq!(env.exit_status, ExitStatus(77));
    }

    #[test]
    fn diverting_rest() {
        let mut env = Env::new_virtual();
        env.builtins.insert("return", return_builtin());
        let list: AndOrList = "return -n 7 || return 0 && X".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Break(Divert::Return(Some(ExitStatus(0)))));
        assert_eq!(env.exit_status, ExitStatus(7));
    }

    #[test]
    fn stack_in_list() {
        fn stub_builtin_condition(
            env: &mut Env<VirtualSystem>,
            _args: Vec<Field>,
        ) -> Pin<Box<dyn Future<Output = yash_env::builtin::Result> + '_>> {
            Box::pin(async move {
                assert_matches!(
                    env.stack.as_slice(),
                    [Frame::Condition, Frame::Builtin { .. }]
                );
                Default::default()
            })
        }
        fn stub_builtin_no_condition(
            env: &mut Env<VirtualSystem>,
            _args: Vec<Field>,
        ) -> Pin<Box<dyn Future<Output = yash_env::builtin::Result> + '_>> {
            Box::pin(async move {
                assert_matches!(env.stack.as_slice(), [Frame::Builtin { .. }]);
                Default::default()
            })
        }

        let mut env = Env::new_virtual();
        env.builtins
            .insert("head", Builtin::new(Special, stub_builtin_condition));
        env.builtins
            .insert("tail", Builtin::new(Special, stub_builtin_no_condition));

        let list: AndOrList = "tail".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));

        let list: AndOrList = "head && head && tail".parse().unwrap();
        let result = list.execute(&mut env).now_or_never().unwrap();
        assert_eq!(result, Continue(()));
    }
}