This crate provides the context macro for adding extra error information to a function.

Works with anyhow, failure and any other error type which provides a context method taking a string.

#
use fn_error_context::context;

#[context("failed to parse config at `{}`", path.as_ref().display())]
pub fn parse_config(path: impl AsRef<Path>) -> anyhow::Result<u32> {
    let text = read_to_string(path.as_ref())?;
    Ok(text.parse()?)
}

let error = parse_config("not-found").unwrap_err();
assert_eq!(
    error.to_string(),
    "failed to parse config at `not-found`",
);
assert_eq!(
    error.source().unwrap().downcast_ref::<io::Error>().unwrap().kind(),
    io::ErrorKind::NotFound,
);

fn-error-context

An attribute macro to add context to errors from a function.

#[context("failed to parse config at `{}`", path.display())]
pub fn parse_config(path: &Path) -> anyhow::Result<u32> {
    let text = read_to_string(path)?;
    Ok(text.parse()?)
}