Dynamic tags alteration

tagger.go

// Route marshaler

// Implements the Marhaler interface of the yaml pkg.
func (p Path) MarshalYAML() (interface{}, error) {
	res, err := marshalYAML("SetTagYAML", p)
	if err != nil {
		return res, fmt.Errorf("failed to marshal yaml: %w", err)
	}

	return string(res), nil
}

func (p Path) SetTagYAML(tag string) string {
	if tag == "route" {
		return p.Route
	}

	return tag
}

func marshalYAML(tagSetter string, marshalObject interface{}) ([]byte, error) {
	out := map[string]interface{}{}
	t := reflect.TypeOf(marshalObject)
	v := reflect.ValueOf(marshalObject)

	funcCtx := v.MethodByName(tagSetter)

	outTag := ""
	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		switch n := f.Tag.Get("yaml"); n {
		case "":
			outTag = f.Name
		case "-":
			outTag = ""
		default:
			outTag = alterTagName(funcCtx, n)
		}
		if outTag != "" {
			out[outTag] = v.Field(i).Interface()
		}
	}

	res, err := yaml.Marshal(out)

	return res, err
}

func alterTagName(funcCtx reflect.Value, params ...interface{}) string {
	in := make([]reflect.Value, len(params))
	for k, param := range params {
		in[k] = reflect.ValueOf(param)
	}

	res := funcCtx.Call(in)[0].String()

	return res
}