stackpulse 0.2.0

use std::fmt;

/// Error type returned by fallible stackpulse APIs.
#[derive(Debug)]
pub enum Error {
    /// I/O or OS error.
    Io(std::io::Error),
    /// A runtime failure with an attached human-readable message.
    RuntimeError(String),
}

/// Convenience alias for `Result<T, Error>` used throughout the crate.
pub type Result<T> = std::result::Result<T, Error>;

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Io(err) => err.fmt(f),
            Self::RuntimeError(message) => f.write_str(message),
        }
    }
}

impl std::error::Error for Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Self::Io(err) => Some(err),
            Self::RuntimeError(_) => None,
        }
    }
}

impl From<std::io::Error> for Error {
    fn from(err: std::io::Error) -> Self {
        Self::Io(err)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn display_and_source_follow_io_error() {
        let err = Error::from(std::io::Error::new(
            std::io::ErrorKind::PermissionDenied,
            "denied",
        ));

        assert_eq!(err.to_string(), "denied");
        assert!(std::error::Error::source(&err).is_some());
    }

    #[test]
    fn display_and_source_follow_runtime_error() {
        let err = Error::RuntimeError("runtime failed".to_string());

        assert_eq!(err.to_string(), "runtime failed");
        assert!(std::error::Error::source(&err).is_none());
    }
}