Here's another demo that annotate errors with custom type.
package main
import (
"fmt"
"io"
"os"
)
type Err struct {
Code string
Message string
Cause error
}
var _ error = Err{}
func (e Err) Error() string {
return fmt.Sprintf("[%s] %s: %s", e.Code, e.Message, e.Cause.Error())
}
// wrapErr annotates an error with code and message
func wrapErr(err error, code string, message string, args ...interface{})
error {
return Err{
Code: code,
Message: fmt.Sprintf(message, args...),
Cause: err,
}
}
// like the proposed try function but with custom wrapper
var try = makeTry(wrapErr)
// use like the proposed try with extra wrapping arguments
func CopyFile(src, dest string) (err error) {
r := try(os.Open(src), "Open", "open %s", src)
defer r.Close()
w := try(os.Create(dest), "Create", "create %s", dest)
defer func() {
w.Close()
if err != nil {
os.Remove(dest)
}
}()
try(io.Copy(w, r)) // bare try without arguments, so no wrapping
try(w.Close())
return nil
}
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