Errors with additional info

[EPashkin]

In https://github.com/gkoz/gir/blob/master/src/config.rs we use this enum for error of configuration processing:

#[derive(Debug)]
pub enum Error {
    CommandLine(DocoptError),
    Io(IoError, PathBuf),
    Toml(String, PathBuf),
    Options(String, PathBuf),
}

Last 3 errors here also contains file name.

Currently for error conversion we use tuple

try!(File::open(&filename)
     .and_then(|mut f| f.read_to_string(&mut input))
     .map_err(|e| (e, &filename)));

with From definition

impl<P: AsRef<OsStr>> From<(IoError, P)> for Error {
    fn from(e: (IoError, P)) -> Error {
        Error::Io(e.0, PathBuf::from(&e.1))
    }
}

This is the normal way to handle errors? Currently seems no way to use this method in quick-error. Can this functionality be added in quick-error?

[tailhook]

Hm, it's interesting. I usually use something like this:

try!(File::open(&filename)
     .and_then(|mut f| f.read_to_string(&mut input))
     .map_err(|e| Error::Io(e, filename.to_path_buf())));

It's a little more verbose. But is it bad enough to require another syntax?

[tailhook]

What I don't like, is writing .to_path_buf(). But instead of magically converting from tuple I'd rather try to implement a conversion function:

impl Error {
  fn io<P:AsRef<Path>>(e: io::Error, path: P) -> Error {
    Error::Io(e, path.as_ref().to_path_buf())
  } 
}
...
try!(File::open(&filename)
     .and_then(|mut f| f.read_to_string(&mut input))
     .map_err(|e| Error::io(e, &filename)));

I'm not sure if we need any shortcut for this.

What do you think?

[EPashkin]

Defining function maybe really better as it clearer declares error type, but extra 7+ characters. Just can't decide :cry:

[tailhook]

I still feel this is an interesting issue, even if we don't know how to approach the issue yet.