src/sys/component_manager/src/clonable_error.rs

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use {
    failure::{self, AsFail, Fail, Error},
    std::fmt,
    std::sync::Arc,
};

/// A wrapper for `Error` that implements `Clone`.
#[derive(Clone)]
pub struct ClonableError {
    err: Arc<Error>,
}

impl AsFail for ClonableError {
    fn as_fail(&self) -> &dyn Fail {
        self.err.as_fail()
    }
}

impl From<Error> for ClonableError {
    fn from(err: Error) -> Self {
        Self { err: Arc::new(err) }
    }
}

impl fmt::Display for ClonableError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.err.fmt(f)
    }
}

impl fmt::Debug for ClonableError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.err.fmt(f)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use {
        failure::format_err,
    };

    #[derive(Debug, Fail, Clone)]
    #[fail(display = "\"{}\" happened: {}", msg, cause)]
    struct FooError {
        msg: String,
        #[fail(cause)]
        cause: ClonableError,
    }

    #[test]
    fn clone() {
        let cause = format_err!("root cause").into();
        let err = FooError {
            msg: "something bad happened".to_string(),
            cause,
        };
        let cloned_err = err.clone();
        assert_eq!(format!("{:?}", err), format!("{:?}", cloned_err));
    }
}