dtolnay/anyhow

Error display inconsistent

hanakannzashi opened this issue · 1 comments

hanakannzashi commented

This is my custom error type

struct MyError;

impl Debug for MyError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        if f.alternate() {
            write!(f, "Debug alternate")
        } else {
            write!(f, "Debug")
        }
    }
}

impl Display for MyError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        if f.alternate() {
            write!(f, "Display alternate")
        } else {
            write!(f, "Display")
        }
    }
}

This is my test result

let err = MyError;
let err_anyhow = anyhow!(MyError);

println!("{}", err);           // Display
println!("{}", err_anyhow);    // Display

println!("{:#}", err);         // Display alternate
println!("{:#}", err_anyhow);  // Display

println!("{:?}", err);         // Debug
println!("{:?}", err_anyhow);  // Display

println!("{:#?}", err);        // Debug alternate
println!("{:#?}", err_anyhow); // Debug alternate

I am quite confused about this result