unwrap.go

package errtrace

import (
	"errors"
	"runtime"
)

// UnwrapFrame unwraps the outermost frame from the given error,
// returning it and the inner error.
// ok is true if the frame was successfully extracted,
// and false otherwise, or if the error is not an errtrace error.
//
// You can use this for structured access to trace information.
//
// Any error that has a method `TracePC() uintptr` will
// contribute a frame to the trace.
func UnwrapFrame(err error) (frame runtime.Frame, inner error, ok bool) { //nolint:revive // error is intentionally middle return
	e, ok := err.(interface{ TracePC() uintptr })
	if !ok {
		return runtime.Frame{}, err, false
	}

	inner = errors.Unwrap(err)
	frames := runtime.CallersFrames([]uintptr{e.TracePC()})
	f, _ := frames.Next()
	if f == (runtime.Frame{}) {
		// Unlikely, but if PC didn't yield a frame,
		// just return the inner error.
		return runtime.Frame{}, inner, false
	}

	return f, inner, true
}