golang wrap 代码
文件路径：/src/errors/wrap.go
/ Copyright 2018 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package errors
import (
"internal/reflectlite"
)
/ Unwrap returns the result of calling the Unwrap method on err, if err's
/ type contains an Unwrap method returning error.
/ Otherwise, Unwrap returns nil.
func Unwrap(err error) error {
u, ok := err.(interface {
Unwrap() error
})
if !ok {
return nil
}
return u.Unwrap()
}
/ Is reports whether any error in err's chain matches target.
/
/ The chain consists of err itself followed by the sequence of errors obtained by
/ repeatedly calling Unwrap.
/
/ An error is considered to match a target if it is equal to that target or if
/ it implements a method Is(error) bool such that Is(target) returns true.
/
/ An error type might provide an Is method so it can be treated as equivalent
/ to an existing error. For example, if MyError defines
/
/ func (m MyError) Is(target error) bool { return target == fs.ErrExist }
/
/ then Is(MyError{}, fs.ErrExist) returns true. See syscall.Errno.Is for
/ an example in the standard library. An Is method should only shallowly
/ compare err and the target and not call Unwrap on either.
func Is(err, target error) bool {
if target == nil {
return err == target
}
isComparable := reflectlite.TypeOf(target).Comparable()
for {
if isComparable && err == target {
return true
}
if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {
return true
}
/ TODO: consider supporting target.Is(err). This would allow
/ user-definable predicates, but also may allow for coping with sloppy
/ APIs, thereby making it easier to get away with them.
if err = Unwrap(err); err == nil {
return false
}
}
}
/ As finds the first error in err's chain that matches target, and if one is found, sets
/ target to that error value and returns true. Otherwise, it returns false.
/
/ The chain consists of err itself followed by the sequence of errors obtained by
/ repeatedly calling Unwrap.
/
/ An error matches target if the error's concrete value is assignable to the value
/ pointed to by target, or if the error has a method As(interface{}) bool such that
/ As(target) returns true. In the latter case, the As method is responsible for
/ setting target.
/
/ An error type might provide an As method so it can be treated as if it were a
/ different error type.
/
/ As panics if target is not a non-nil pointer to either a type that implements
/ error, or to any interface type.
func As(err error, target any) bool {
if target == nil {
panic("errors: target cannot be nil")
}
val := reflectlite.ValueOf(target)
typ := val.Type()
if typ.Kind() != reflectlite.Ptr || val.IsNil() {
panic("errors: target must be a non-nil pointer")
}
targetType := typ.Elem()
if targetType.Kind() != reflectlite.Interface && !targetType.Implements(errorType) {
panic("errors: *target must be interface or implement error")
}
for err != nil {
if reflectlite.TypeOf(err).AssignableTo(targetType) {
val.Elem().Set(reflectlite.ValueOf(err))
return true
}
if x, ok := err.(interface{ As(any) bool }); ok && x.As(target) {
return true
}
err = Unwrap(err)
}
return false
}
var errorType = reflectlite.TypeOf((*error)(nil)).Elem()