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//go:build !go1.20
// +build !go1.20
package errors
// Disclaimer: functions Join and Unwrap are copied from the stdlib errors
// package v1.21.0.
// Join returns an error that wraps the given errors.
// Any nil error values are discarded.
// Join returns nil if every value in errs is nil.
// The error formats as the concatenation of the strings obtained
// by calling the Error method of each element of errs, with a newline
// between each string.
//
// A non-nil error returned by Join implements the Unwrap() []error method.
func Join(errs ...error) error {
n := 0
for _, err := range errs {
if err != nil {
n++
}
}
if n == 0 {
return nil
}
e := &joinError{
errs: make([]error, 0, n),
}
for _, err := range errs {
if err != nil {
e.errs = append(e.errs, err)
}
}
return e
}
type joinError struct {
errs []error
}
func (e *joinError) Error() string {
var b []byte
for i, err := range e.errs {
if i > 0 {
b = append(b, '\n')
}
b = append(b, err.Error()...)
}
return string(b)
}
func (e *joinError) Unwrap() []error {
return e.errs
}
// 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.
//
// Unwrap only calls a method of the form "Unwrap() error".
// In particular Unwrap does not unwrap errors returned by [Join].
func Unwrap(err error) error {
u, ok := err.(interface {
Unwrap() error
})
if !ok {
return nil
}
return u.Unwrap()
}
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