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snafu 0.6.10

An ergonomic error handling library
Documentation 
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use snafu::Snafu;

#[derive(Debug, Snafu)]
enum InnerError {
    Boom,
}

fn inner() -> Result<(), InnerError> {
    Ok(())
}

mod enabling {
    use super::*;
    use snafu::{ResultExt, Snafu};

    #[derive(Debug, Snafu)]
    enum Error {
        NoArgument {
            #[snafu(source)]
            cause: InnerError,
        },

        ExplicitTrue {
            #[snafu(source(true))]
            cause: InnerError,
        },

        FromImpliesTrue {
            #[snafu(source(from(InnerError, Box::new)))]
            cause: Box<InnerError>,
        },

        ExplicitFalse {
            #[snafu(source(false))]
            source: i32,
        },
    }

    fn example() -> Result<(), Error> {
        inner().context(NoArgument)?;
        inner().context(ExplicitTrue)?;
        inner().context(FromImpliesTrue)?;
        ExplicitFalse { source: 42 }.fail()?;
        Ok(())
    }

    #[test]
    fn implements_error() {
        fn check<T: std::error::Error>() {}
        check::<Error>();
        example().unwrap_err();
    }
}

mod transformation {
    use super::*;
    use snafu::{ResultExt, Snafu};
    use std::io;

    #[derive(Debug, Snafu)]
    enum Error {
        TransformationViaClosure {
            #[snafu(source(from(InnerError, |e| io::Error::new(io::ErrorKind::InvalidData, e))))]
            source: io::Error,
        },

        TransformationViaFunction {
            #[snafu(source(from(InnerError, into_io)))]
            source: io::Error,
        },

        TransformationToTraitObject {
            #[snafu(source(from(InnerError, Box::new)))]
            source: Box<dyn std::error::Error>,
        },
    }

    fn into_io(e: InnerError) -> io::Error {
        io::Error::new(io::ErrorKind::InvalidData, e)
    }

    fn example() -> Result<(), Error> {
        inner().context(TransformationViaClosure)?;
        inner().context(TransformationViaFunction)?;
        inner().context(TransformationToTraitObject)?;
        Ok(())
    }

    #[test]
    fn implements_error() {
        fn check<T: std::error::Error>() {}
        check::<Error>();
        example().unwrap();
    }

    #[derive(Debug, Snafu)]
    #[snafu(source(from(Error, Box::new)))]
    struct ApiError(Box<Error>);

    fn api_example() -> Result<(), ApiError> {
        example()?;
        Ok(())
    }

    #[test]
    fn api_implements_error() {
        fn check<T: std::error::Error>() {}
        check::<ApiError>();
        api_example().unwrap();
    }
}