restic/internal/errors/errors.go

package errors

import (
	"net/url"

	"github.com/pkg/errors"
)

// New creates a new error based on message. Wrapped so that this package does
// not appear in the stack trace.
var New = errors.New

// Errorf creates an error based on a format string and values. Wrapped so that
// this package does not appear in the stack trace.
var Errorf = errors.Errorf

// Wrap wraps an error retrieved from outside of restic. Wrapped so that this
// package does not appear in the stack trace.
var Wrap = errors.Wrap

// Wrapf returns an error annotating err with the format specifier. If err is
// nil, Wrapf returns nil.
var Wrapf = errors.Wrapf

// WithMessage annotates err with a new message. If err is nil, WithMessage
// returns nil.
var WithMessage = errors.WithMessage

// Cause returns the cause of an error. It will also unwrap certain errors,
// e.g. *url.Error returned by the net/http client.
func Cause(err error) error {
	type Causer interface {
		Cause() error
	}

	for {
		// unwrap *url.Error
		if urlErr, ok := err.(*url.Error); ok {
			err = urlErr.Err
			continue
		}

		// if err is a Causer, return the cause for this error.
		if c, ok := err.(Causer); ok {
			err = c.Cause()
			continue
		}

		break
	}

	return err
}