pass source error to with_context closure?

[miquels]

I like to log the Display version of an error instead of the Debug version, because it's then all on one line which I like better for logfiles. However there is currently no way to log the original error. I would like to be able to do:

    let content = fs::read(&path)
        .with_context(|e| format!("failed to read instrs from {}: {}", path.display(), e));

It's probably too late to change with_context to take an argument - besides, it would not make sense for Options. Maybe error_context? POC here: https://github.com/miquels/anyhow/commit/4a79660fa0588c097b9ae3d143bb7e54b928b97b

[dtolnay]

I would recommend not putting the cause's message into the outer error's message. Instead you can print the causes in whatever formatting you want, such as separated by ::

print!("{}", error);
error.chain().skip(1).for_each(|e| print!(": {}", e));

If you want the cause to appear in the outer error's message anyway, you would use map_err:

let content = fs::read(&path)
    .map_err(|e| {
        let context = format!("failed to read instrs from {}: {}", path.display(), e);
        Error::new(e).context(context)
    })?;

[miquels]

Okay, thanks. I'll probably write some macros to do it that way, then.