Links and custom description / display

[theduke]

One thing I really dislike about error_chain compared to quick_error is the inability to add a custom description and format to foreign_link errors (and regular links as well, actually).

The docs suggest using chain_err, but this looses the type information for the cause, which is not ideal, and you have to implement From manually.

Any plans to add that functionality?

error_chain! {
    foreign_links {
        Io(e: ::std::io::Error) {
            description("disk_io")
            display("Could not read/write from disk: '{}'", e)
        }
    }
}

[theduke]

Upon investigation, you can get almost the described behaviour:

error_chain! {
  errors {
    Io(e: io::Error) {
      description(..)
      display(..)
      cause(&e)
      from()
    }
  }
}

The only thing missing is, this only gives a From implementation for io::Error to ErrorKind, and you need to implement From manually.

[Arnavion]

cause() and from() don't do anything in error-chain. You can remove them.

>you need to implement From manually.

Why do you need to implement manually? If you're talking about an impl for io::Error -> Error, it's unnecessary since impls for io::Error -> ErrorKind and ErrorKind -> Error are already generated.

Edit: Sorry, I misread that you switched to using custom links in your second post.