[feature] errors.Unwrap

[pkg]

[feature] errors.Unwrap

[powerman]

@davecheney Maybe it's worth to reconsider this now? It may be very useful to provide Unwrap() compatible with stdlib's errors, to make it easier to migrate existing codebase from pkg/errors to stdlib's errors or use both in parallel.

I mean, I'd like to replace errors.Cause() with errors.Is() in existing code, but this require pkg/errors to support Unwrap().

[davecheney]

I'm going to close this as I think it's going in the wrong direction.

The original design of this errors package mirror'd Juju's which requires callers to manually wrap each level of error return to record a stack trace. Apart from this being incomplete and verbose, on reflection I think the natural stack trace recorded at the point the error happens is probably good enough (tm) for most use cases. In the cases where they are not, errors.Wrap allows the caller to add additional context to the error path.

In either cases the printing of this stack detail, including the nested stacks now possible since #27 makes this method less useful.

[jaekwon]

Related proposed solution: #144