You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
106 lines
3.0 KiB
106 lines
3.0 KiB
// 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 xerrors |
|
|
|
import ( |
|
"reflect" |
|
) |
|
|
|
// A Wrapper provides context around another error. |
|
type Wrapper interface { |
|
// Unwrap returns the next error in the error chain. |
|
// If there is no next error, Unwrap returns nil. |
|
Unwrap() error |
|
} |
|
|
|
// Opaque returns an error with the same error formatting as err |
|
// but that does not match err and cannot be unwrapped. |
|
func Opaque(err error) error { |
|
return noWrapper{err} |
|
} |
|
|
|
type noWrapper struct { |
|
error |
|
} |
|
|
|
func (e noWrapper) FormatError(p Printer) (next error) { |
|
if f, ok := e.error.(Formatter); ok { |
|
return f.FormatError(p) |
|
} |
|
p.Print(e.error) |
|
return nil |
|
} |
|
|
|
// Unwrap returns the result of calling the Unwrap method on err, if err implements |
|
// Unwrap. Otherwise, Unwrap returns nil. |
|
func Unwrap(err error) error { |
|
u, ok := err.(Wrapper) |
|
if !ok { |
|
return nil |
|
} |
|
return u.Unwrap() |
|
} |
|
|
|
// Is reports whether any error in err's chain matches target. |
|
// |
|
// 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. |
|
func Is(err, target error) bool { |
|
if target == nil { |
|
return err == target |
|
} |
|
|
|
isComparable := reflect.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 supporing 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 the type to which target |
|
// points, and if so, sets the target to its value and returns true. An error |
|
// matches a type if it is assignable to the target type, or if it has a method |
|
// As(interface{}) bool such that As(target) returns true. As will panic if target |
|
// is not a non-nil pointer to a type which implements error or is of interface type. |
|
// |
|
// The As method should set the target to its value and return true if err |
|
// matches the type to which target points. |
|
func As(err error, target interface{}) bool { |
|
if target == nil { |
|
panic("errors: target cannot be nil") |
|
} |
|
val := reflect.ValueOf(target) |
|
typ := val.Type() |
|
if typ.Kind() != reflect.Ptr || val.IsNil() { |
|
panic("errors: target must be a non-nil pointer") |
|
} |
|
if e := typ.Elem(); e.Kind() != reflect.Interface && !e.Implements(errorType) { |
|
panic("errors: *target must be interface or implement error") |
|
} |
|
targetType := typ.Elem() |
|
for err != nil { |
|
if reflect.TypeOf(err).AssignableTo(targetType) { |
|
val.Elem().Set(reflect.ValueOf(err)) |
|
return true |
|
} |
|
if x, ok := err.(interface{ As(interface{}) bool }); ok && x.As(target) { |
|
return true |
|
} |
|
err = Unwrap(err) |
|
} |
|
return false |
|
} |
|
|
|
var errorType = reflect.TypeOf((*error)(nil)).Elem()
|
|
|