failure_derive 0.1.0

extern crate failure;
#[macro_use] extern crate failure_derive;

use std::io;
use std::fmt;

use failure::{Backtrace, Fail};

#[derive(Fail, Debug)]
#[fail(display = "An error has occurred: {}", inner)]
struct WrapError {
    #[cause] inner: io::Error,
}

#[test]
fn wrap_error() {
    let inner = io::Error::from_raw_os_error(98);
    let err = WrapError { inner };
    assert!(err.cause().and_then(|err| err.downcast_ref::<io::Error>()).is_some());
}

#[derive(Fail, Debug)]
#[fail(display = "An error has occurred: {}", _0)]
struct WrapTupleError(#[cause] io::Error);

#[test]
fn wrap_tuple_error() {
    let io_error = io::Error::from_raw_os_error(98);
    let err: WrapTupleError = WrapTupleError(io_error);
    assert!(err.cause().and_then(|err| err.downcast_ref::<io::Error>()).is_some());
}

#[derive(Fail, Debug)]
#[fail(display = "An error has occurred: {}", inner)]
struct WrapBacktraceError {
    #[cause] inner: io::Error,
    backtrace: Backtrace,
}

#[test]
fn wrap_backtrace_error() {
    let inner = io::Error::from_raw_os_error(98);
    let err: WrapBacktraceError = WrapBacktraceError { inner, backtrace: Backtrace::new() };
    assert!(err.cause().and_then(|err| err.downcast_ref::<io::Error>()).is_some());
    assert!(err.backtrace().is_some());
}

#[derive(Fail, Debug)]
enum WrapEnumError {
    #[fail(display = "An error has occurred: {}", _0)]
    Io(#[cause] io::Error),
    #[fail(display = "An error has occurred: {}", inner)]
    Fmt {
        #[cause] inner: fmt::Error,
        backtrace: Backtrace,
    },
}

#[test]
fn wrap_enum_error() {
    let io_error = io::Error::from_raw_os_error(98);
    let err: WrapEnumError = WrapEnumError::Io(io_error);
    assert!(err.cause().and_then(|err| err.downcast_ref::<io::Error>()).is_some());
    assert!(err.backtrace().is_none());
    let fmt_error = fmt::Error::default();
    let err: WrapEnumError = WrapEnumError::Fmt { inner: fmt_error, backtrace: Backtrace::new() };
    assert!(err.cause().and_then(|err| err.downcast_ref::<fmt::Error>()).is_some());
    assert!(err.backtrace().is_some());
}