Crate source_chain

source-chain

Formats StdError with it’s source chain

#[derive(Debug, thiserror::Error)]
enum Error {
    #[error("unknown file {1}")]
    UnknownFile(#[source] std::io::Error, &'static str),
}

fn file_error() -> Result<String, Error> {
    let filename = "unknown-file.txt";
    std::fs::read_to_string(filename).map_err(|e| Error::UnknownFile(e, filename))
}

let err = file_error().unwrap_err();
assert_eq!(
    source_chain::to_string(&err),
    "unknown file unknown-file.txt\nCaused by:\n\tNo such file or directory (os error 2)"
);

let dyn_err: Box<dyn std::error::Error> = Box::new(err);
assert_eq!(
    // notice dereferencing
    source_chain::to_string(&*dyn_err),
    "unknown file unknown-file.txt\nCaused by:\n\tNo such file or directory (os error 2)"
);

Functions

to_string

A helper function to format an error with its source chain.