rclone/lib/errors/errors.go

75 lines
2.0 KiB
Go

// Package errors provides error handling utilites.
package errors
import (
"reflect"
)
// WalkFunc is the signature of the Walk callback function. The function gets the
// current error in the chain and should return true if the chain processing
// should be aborted.
type WalkFunc func(error) bool
// Walk invokes the given function for each error in the chain. If the
// provided functions returns true or no further cause can be found, the process
// is stopped and no further calls will be made.
//
// The next error in the chain is determined by the following rules:
//
// the return value of this method is used.
// - If the current error has a `Unwrap() error` method
// the return value of this method is used.
// - If the current error has a `Unwrap() []error` method
// the return values of this method is used.
// - Common errors in the Go runtime that contain an Err field will use this value.
func Walk(err error, f WalkFunc) {
for prev := err; err != nil; prev = err {
if f(err) {
return
}
switch e := err.(type) {
case multiWrapper:
for _, err = range e.Unwrap() {
Walk(err, f)
}
return
case causer:
err = e.Cause()
case wrapper:
err = e.Unwrap()
default:
// Unpack any struct or *struct with a field of name Err which satisfies
// the error interface. This includes *url.Error, *net.OpError,
// *os.SyscallError and many others in the stdlib.
errType := reflect.TypeOf(err)
errValue := reflect.ValueOf(err)
if errValue.IsValid() && errType.Kind() == reflect.Ptr {
errType = errType.Elem()
errValue = errValue.Elem()
}
if errValue.IsValid() && errType.Kind() == reflect.Struct {
if errField := errValue.FieldByName("Err"); errField.IsValid() {
errFieldValue := errField.Interface()
if newErr, ok := errFieldValue.(error); ok {
err = newErr
}
}
}
}
if reflect.DeepEqual(err, prev) {
break
}
}
}
type causer interface {
Cause() error
}
type wrapper interface {
Unwrap() error
}
type multiWrapper interface {
Unwrap() []error
}