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//! Helpers for error handling.

/// Format an error, including its chain of sources.
///
/// Always use this when displaying an error, especially `anyhow::Error`.
pub fn format(error: impl AsRef<dyn std::error::Error>) -> String {
    format_ref(error.as_ref())
}

/// Format an error, including its chain of sources.
///
/// Always use this when displaying an error, especially `anyhow::Error`.
pub fn format_ref(error: &dyn std::error::Error) -> String {
    let mut string = error.to_string();
    for source in std::iter::successors(error.source(), |error| error.source()) {
        string.push_str(" -> ");
        string.push_str(&source.to_string());
    }
    string
}

#[test]
fn test_format() {
    let err = anyhow::format_err!("root_cause")
        .context("inner_context")
        .context("outer_context");

    assert_eq!(err.to_string(), "outer_context"); // Oh no, we don't see the root cause!

    // Now we do:
    assert_eq!(format(&err), "outer_context -> inner_context -> root_cause");
}