converting `impl Error` to `Diagnostic` implicitly when using with_err or cascading error using `?`

[LordMZTE]

When using miette, I have this sort of code a lot:

use miette::{WithErr, Result};

fn main() -> Result<()> {
    // do_stuff returns a `Result<T, E>` where E implements the `Error` trait.
    do_stuff().into_diagnostic().with_err("failed to do stuff")?;

    // or without with_err
    do_stuff().into_diagnostic()?;

    Ok(())
}

and this results in many calls to into_diagnostic, which can get quite annoying. However, we could implement impl From<E: Error> for Report in order to be able to simplify the above code to something like this:

use miette::{IntoDiagnostic, WithErr, Result};

fn main() -> Result<()> {
    // do_stuff returns a `Result<T, E>` where E implements the `Error` trait.
    do_stuff().with_err("failed to do stuff")?;

    // or without with_err
    do_stuff()?;

    Ok(())
}

Is there any reason this is currently not possible? Has this just not been implemented or is doing this (in a binary crate) an antipattern? If so, how to do it better?

[zkat]

It's unfortunate, but I can't make that go away because eyreish (the thing that makes miette::Result work) has to specialize on Diagnostic, not Error under the hood. And there's no way to handle both that I could figure out.

The plan for this particular wart is that it'll go away once provide-any is stabilized, since we'll be able to yank out eyreish altogether and miette will be able to provide a plain ol' EyreHandler to do all its fancy printing, instead, at that point :)

Sorry for the hassle. I've found that having a lot of .into_diagnostic()s is a good sign, for me, that maybe I should just make my own error type using thiserror, with #[from] impls, but I know that's also a bit more of a hassle than someone might want out of something like miette::Result that's meant to remove exactly that kind of extra work?

[LordMZTE]

Thanks for the explanation! I do think that this would make miette a whole lot more convenient to use, so I think it's a great idea to change this.

[zkat]

If you have any ideas on what could actually work to remove this .into_diagnostic() thing, I would LOVE to hear them, btw!

[LordMZTE]

I've not taken a close look at miette's codebase yet, so I'm not sure I'll have any ideas. Once we do come up with a plan on how to go on with this, I'd be happy to contribute tho!

[Christoph-AK]

Hi there, was there any change since 2021 making this more realistic to implement by now? I'm currently evaluating the use of miette for my work, but not having the easy ? is a extremely annoying and bloats the already verbose rust code even more. (Don't get me wrong, love the explicitness of rust, but at this point I am basically doing a Ctrl-H "?" -> ".into_diagnostic()?".)

Isn't this a beauty :D