how to ingest anyhow::Error?  #755

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1. Alfred-Mountfield commented on Jul 6, 2022

   

   Alfred-Mountfield

   on Jul 6, 2022

   Last edited by Alfred-Mountfield

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   Are you able to fix some of the formatting on your post? I'm finding it a little difficult to know what types you're dealing with.

   For example is this:

   std::result::Result<T, error_stack::Reportanyhow::Error>

   meant to be std::result::Result<T, error_stack::Report<anyhow::Error>>?

   Because if so it's likely failing because you're trying to turn a Report into a Report.
2. sdwoodbury commented on Jul 6, 2022

   

   sdwoodbury

   on Jul 6, 2022

   Last edited by sdwoodbury

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   @Alfred-Mountfield thanks for the help. I'm still learning how to decipher larger error messages. You're correct.

   in case anyone else has this question, I'll show the work around I found, after I understood what was happening:

   1. match on the anyhow::Error
   2. On Err, turn it into Err(Report::new(e.into()))

   example:

   let res: Result<_, MyError> = match thing_that_returns_anyhow_error {
       Ok(r) => Ok(r),
      Err(e) => Err(Report::new::(e.into()))
   };
   
   let thing_i_wanted = res.attach_printable(...)?;
   

   also had to do this:

   impl std::convert::From<anyhow::Error> for MyError {
       fn from(err: anyhow::Error) -> MyError {
           MyError { ...) }
       }
   } 
   

   Is there a better way to do this? This is fine I suppose, it just doesn't feel ergonomic and I expect to encounter this difficulty quite frequently. It would be nice if all MyError had to do was implement From.
3. Alfred-Mountfield commented on Jul 6, 2022

   

   Alfred-Mountfield

   on Jul 6, 2022

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   Thanks for the expanded code, it helps a lot!

   So the main problem you're encountering with this is that anyhow isn't really designed to be a library friendly implementation. It is very opinionated, which is great when you're only using anyhow (which is what it's designed for), where you change your Error types to anyhow::Error.

   They've made an active decision to not implement std::error::Error for anyhow::Error which basically forces you to only use their error type in signatures and such. (Again, not a criticism, it's just the philosophy of their library, it's a trade-off for other benefits).

   We've provided a blanket implementation of Context for std::error::Error for convenience but because of the above this doesn't cover anyhow::Error. So at the moment your approach might be the best solution if you want to continue to use anyhow, however I'd consider anyhow and error-stack as different approaches, rather than something to be used in tandem.

   Maybe some of the comments in this discussion will help capture the philosophy too :)
4. hashintel

   locked and limited conversation to collaborators on Jul 6, 2022
5. Alfred-Mountfield

   converted this issue into a discussion #761 on Jul 6, 2022