Use google.protobuf.Value in a protobuf file with go interface{} field in a struct and vice versa

Question

I have protobuf message which looks like this :

// Rule : Includes an entity , an operation and a comparison value
message Rule {
  string entity = 1;
  string operator = 2;
  google.protobuf.Value value = 3;
}

I am using Value here because value can be of any type.

In my Golang code where I am using the generated code :

type Rule struct {
 Entity string
 Operator string
 Value interface{}
}

Now, My question is : How do I convert type represented by Kind of google.protobuf.Value (nil, number, string, bool, struct, list) to interface{} and convert the dynamic type of interface{} in runtime back to type google.protobuf.Value ?

I can really use some help, found a sorta-solution here ( https://go.googlesource.com/protobuf/+/4c057caa84dc5e1bc6bf0d9fe8af9180a6151e07/internal/value/convert.go ) but was hoping of a simpler way to go about this.

Answer 1

Commenting for the sake of completeness :

func convertToValue(v interface{}, from reflect.Type) (*types.Value, error) {
    switch from.Kind() {
    case reflect.String:
        if reflect.ValueOf(v).String() == "true" || reflect.ValueOf(v).String() == "false" {
            boolVal, err := strconv.ParseBool(reflect.ValueOf(v).String())
            if err != nil {
                return nil, err
            }
            return &types.Value{Kind:&types.Value_BoolValue{BoolValue:boolVal}}, nil
        }
        return &types.Value{Kind:&types.Value_StringValue{StringValue:reflect.ValueOf(v).String()}}, nil
    case reflect.Int64:
    case reflect.Float64:
        return &types.Value{Kind:&types.Value_NumberValue{NumberValue:reflect.ValueOf(v).Float()}}, nil
    case reflect.Slice:
        list := reflect.ValueOf(v)
        outputList := make([]*types.Value,0)
        for i:=0 ; i < list.Len(); i++ {
            val, err := convertToValue(list.Index(i).Interface(), reflect.TypeOf(list.Index(i).Interface()))
            if err != nil {
                return nil, err
            }
            outputList = append(outputList, val)
        }
        return &types.Value{Kind:&types.Value_ListValue{ListValue:&types.ListValue{Values:outputList}}}, nil
    case reflect.Struct:
        valStruct := reflect.ValueOf(v)
        outputMap := make(map[string]*types.Value)
        numOfField := valStruct.NumField()
        for i := 0; i < numOfField; i++ {
            val, err := convertToValue(valStruct.Field(i).Interface(), reflect.TypeOf(valStruct.Field(i).Interface()))
            if err != nil {
                return nil, err
            }
            outputMap[valStruct.Field(i).Type().Name()] = val
        }

        return &types.Value{Kind:&types.Value_StructValue{StructValue:&types.Struct{Fields:outputMap}}}, nil
    default:
        return nil, nil
}

and

func convertValueToInterface(value types.Value) (interface{}, error) {

    switch {
    case _ , ok := value.Kind.(*types.Value_NullValue); ok:
        return nil, nil
    case x , ok := value.Kind.(*types.Value_StringValue); ok:
        return x.StringValue, nil
    case x , ok := value.Kind.(*types.Value_NumberValue); ok:
        return x.NumberValue, nil
    case x , ok := value.Kind.(*types.Value_BoolValue); ok:
        return strconv.FormatBool(x.BoolValue), nil
    case x , ok := value.Kind.(*types.Value_ListValue); ok:
        if x == nil || x.ListValue == nil || x.ListValue.Values == nil {
            return nil, nil
        }
        listValue := x.ListValue.Values
        if len(listValue) == 0 {
            return nil, nil
        }
        val, err := convertValueToInterface(*listValue[0])
        if err != nil {
            return nil, err
        }
        typ := reflect.TypeOf(val)
        outputList := reflect.MakeSlice(reflect.SliceOf(typ),0,0)
        for _, value := range listValue {
            if value != nil {
                val, err := convertValueToInterface(*value)
                if err != nil {
                    return nil, err
                }
                outputList = reflect.Append(outputList, reflect.ValueOf(val))
            }
        }
        return outputList.Interface(), nil
    case x , ok := value.Kind.(*types.Value_StructValue); ok:
        if x == nil || x.StructValue == nil || x.StructValue.Fields == nil {
            return nil, nil
        }
        mapValue := x.StructValue.Fields
        var keyTyp reflect.Type
        var typ reflect.Type
        for key,value := range mapValue {
            if value != nil {
                val, err := convertValueToInterface(*value)
                if err != nil {
                    return nil, err
                }
                keyTyp = reflect.TypeOf(key)
                typ = reflect.TypeOf(val)
                break
            } else {
                return nil, nil
            }
        }
        outputMap := reflect.MakeMap(reflect.MapOf(keyTyp, typ))
        for key,value := range mapValue {
            if value != nil {
                val, err := convertValueToInterface(*value)
                if err != nil {
                    return nil, err
                }
                outputMap.SetMapIndex(reflect.ValueOf(key), reflect.ValueOf(val))
            }
        }
        return outputMap.Interface(), nil
    default:
        return nil, nil
}