watchexec/crates/lib/src/command/shell.rs

use tokio::process::Command;
use tracing::trace;

/// Shell to use to run commands.
///
/// `Cmd` and `Powershell` are special-cased because they have different calling conventions. Also
/// `Cmd` is only available in Windows, while `Powershell` is also available on unices (provided the
/// end-user has it installed, of course).
///
/// See [`Config.cmd`] for the semantics of `None` vs the other options.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Shell {
	/// Use no shell, and execute the command directly.
	///
	/// This is the default, however as consumer of this library you are encouraged to set your own
	/// default as makes sense in your application / for your platform.
	None,

	/// Use the given string as a unix shell invocation.
	///
	/// This means two things:
	/// - the program is invoked with `-c` followed by the command, and
	/// - the string will be split on space, and the resulting vec used as execvp(3) arguments:
	///   first is the shell program, rest are additional arguments (which come before the `-c`
	///   mentioned above). This is a very simplistic approach deliberately: it will not support
	///   quoted arguments, for example. Use [`Shell::None`] with a custom command vec for that.
	Unix(String),

	/// Use the Windows CMD.EXE shell.
	///
	/// This is invoked with `/C` followed by the command.
	#[cfg(windows)]
	Cmd,

	/// Use Powershell, on Windows or elsewhere.
	///
	/// This is invoked with `-Command` followed by the command.
	///
	/// This is preferred over `Unix("pwsh")`, though that will also work on unices due to
	/// Powershell supporting the `-c` short option.
	Powershell,
}

impl Default for Shell {
	fn default() -> Self {
		Self::None
	}
}

impl Shell {
	/// Obtain a [`Command`] given a list of command parts.
	///
	/// Behaves as described in the enum documentation.
	///
	/// # Panics
	///
	/// - Panics if `cmd` is empty.
	/// - Panics if the string in the `Unix` variant is empty or only whitespace.
	pub fn to_command(&self, cmd: &[String]) -> Command {
		assert!(!cmd.is_empty(), "cmd was empty");
		trace!(shell=?self, ?cmd, "constructing command");

		match self {
			Shell::None => {
				// UNWRAP: checked by assert
				#[allow(clippy::unwrap_used)]
				let (first, rest) = cmd.split_first().unwrap();
				let mut c = Command::new(first);
				c.args(rest);
				c
			}

			#[cfg(windows)]
			Shell::Cmd => {
				let mut c = Command::new("cmd.exe");
				c.arg("/C").arg(cmd.join(" "));
				c
			}

			Shell::Powershell if cfg!(windows) => {
				let mut c = Command::new("powershell.exe");
				c.arg("-Command").arg(cmd.join(" "));
				c
			}

			Shell::Powershell => {
				let mut c = Command::new("pwsh");
				c.arg("-Command").arg(cmd.join(" "));
				c
			}

			Shell::Unix(name) => {
				assert!(!name.is_empty(), "shell program was empty");
				let sh = name.split_ascii_whitespace().collect::<Vec<_>>();

				// UNWRAP: checked by assert
				#[allow(clippy::unwrap_used)]
				let (shprog, shopts) = sh.split_first().unwrap();

				let mut c = Command::new(shprog);
				c.args(shopts);
				c.arg("-c").arg(cmd.join(" "));
				c
			}
		}
	}
}

#[cfg(test)]
mod test {
	use super::Shell;
	use command_group::AsyncCommandGroup;

	#[tokio::test]
	#[cfg(unix)]
	async fn unix_shell_default() -> Result<(), std::io::Error> {
		assert!(Shell::default()
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(unix)]
	async fn unix_shell_none() -> Result<(), std::io::Error> {
		assert!(Shell::None
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(unix)]
	async fn unix_shell_alternate() -> Result<(), std::io::Error> {
		assert!(Shell::Unix("bash".into())
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(unix)]
	async fn unix_shell_alternate_shopts() -> Result<(), std::io::Error> {
		assert!(Shell::Unix("bash -o errexit".into())
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(windows)]
	async fn windows_shell_default() -> Result<(), std::io::Error> {
		assert!(Shell::default()
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(windows)]
	async fn windows_shell_cmd() -> Result<(), std::io::Error> {
		assert!(Shell::Cmd
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(windows)]
	async fn windows_shell_powershell() -> Result<(), std::io::Error> {
		assert!(Shell::Powershell
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}

	#[tokio::test]
	#[cfg(windows)]
	async fn windows_shell_unix_style_powershell() -> Result<(), std::io::Error> {
		assert!(Shell::Unix("powershell.exe".into())
			.to_command(&["echo".into(), "hi".into()])
			.group_status()
			.await?
			.success());
		Ok(())
	}
}