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// Package xerrors contains extensions to the standard library package errors.
package xerrors
import (
"errors"
"runtime"
"strconv"
"strings"
)
type withStack struct {
inner error
pc []uintptr
}
func (err withStack) Error() string {
var sb strings.Builder
frames := runtime.CallersFrames(err.pc)
_, _ = sb.WriteString(err.inner.Error())
_, _ = sb.WriteString("\n\n")
for {
frame, more := frames.Next()
_, _ = sb.WriteString(frame.Function)
_, _ = sb.WriteString("(...)\n ")
_, _ = sb.WriteString(frame.File)
_, _ = sb.WriteString(":")
_, _ = sb.WriteString(strconv.Itoa(frame.Line))
_, _ = sb.WriteString("\n")
if !more {
break
}
}
return sb.String()
}
func (err withStack) Unwrap() error {
return err.inner
}
var noError = errors.New("no error")
// WithStack returns an error that wraps err and adds the call stack of the call to WithStack to
// Error(). If err is nil or already has a stack attached, returns err.
func WithStack(err error) error {
if err == nil {
return nil
}
// use noError in case anything along err's chain has a custom Is that calls Error() for some
// reason.
if errors.Is(err, withStack{inner: noError}) {
return err
}
var buf [64]uintptr
var ptrs []uintptr
skip := 2
for {
n := runtime.Callers(skip, buf[:])
ptrs = append(ptrs, buf[:n]...)
if n < len(buf) {
break
}
skip += n
}
return withStack{
inner: err,
pc: ptrs,
}
}
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