Converting from anyhow::Error

[akshayknarayan]

Hi,
I am porting multiple crates from anyhow to eyre, so I have code that looks something like this:

fn foo() -> Result<(), anyhow::Error> {
  Ok(())
}

fn bar() -> Result<(), eyre::Report> {
  let f = foo().map_err(|e| eyre::Report::new(e))?;
  Ok(())
}

This, as expected, gives

error[E0277]: the trait bound `anyhow::Error: std::error::Error` is not satisfied
  --> src/lib.rs:6:49
   |
6  |     let f = foo().map_err(|e| eyre::Report::new(e))?;
   |                                                 ^ the trait `std::error::Error` is not implemented for `anyhow::Error`
   |
  ::: /home/akshayn/.cargo/registry/src/github.com-1ecc6299db9ec823/eyre-0.6.0/src/error.rs:21:12
   |
21 |         E: StdError + Send + Sync + 'static,
   |            -------- required by this bound in `eyre::error::<impl eyre::Report>::new`

error: aborting due to previous error

Since anyhow::Error and eyre::Report are so similar, is there a better way to construct an eyre::Report mid-stack than this, which is sad and throws out the context:

fn foo() -> Result<(), anyhow::Error> {
  Ok(())
}

fn bar() -> Result<(), eyre::Report> {
  let f = foo().map_err(|e| eyre::eyre!("{:?}", e))?;
  Ok(())
}

Thanks for the help!

[yaahc]

the best way to convert between the two would be to first convert the anyhow::Error to a Box<dyn Error> and then convert that to an Eyre report with the macro. that way you'll preserve the chain of sources at least, though you'll still lose the backtrace that anyhow captured originally.

[akshayknarayan]

that makes sense, thanks!

[Arjentix]

Just for future readers:

foo().map_err(|err| eyre!(Box::new(err))

[pksunkara]

though you'll still lose the backtrace that anyhow captured originally.

verbosity of code to convert

With both the above issues in mind, is it worth adding some code in this crate under anyhow-compat feature to add support to use ? on anyhow errors to convert them eyre errors easily?

[ppoliani]

map_err(|err| eyre!(Box::new(err))

Alternatively you can wrap this inside a declarative macro

map_err!(foo())?;

#[macro_export]
macro_rules! map_err {
  ($fun:expr) => {
    $fun.map_err(|e| eyre!(Box::new(e)))
  }
}

[pksunkara]

@yaahc Please let me know if you welcome a PR

[yaahc]

@yaahc Please let me know if you welcome a PR

I've no objections to adding an anyhow_compat feature, PRs welcome

[thewh1teagle]

What's the status of this feature?
I would like to use ? on anyhow results on functions which return eyre::Result.

[Danvil]

I would also be interested in that. Some other coded in my project uses anyhow and manually mapping the errors is quite a pain..