how to know whether field has options while converting proto to other language

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LakshmiKanth Gupta

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Dec 5, 2019, 3:26:15 PM12/5/19
to Protocol Buffers
Hi,

Currently I am writing a convertor from proto format to ttcn3 format.

Messages which I have defined has some custom Field options. How can I check whether a field has custom options or not.


syntax="proto3";
import "google/protobuf/descriptor.proto"
extend google.protobuf.FieldOptions{
   bool presence=50001;
}

message Mymessage
{
    int32 foo=1[(presence)=true];
    string bar=2;
}

This is my file. I would like to know when my convertor is invoked using protoc whether a field has options defined or not.

Thanks in advance,

with best regards,
  Gupta

Adam Cozzette

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Dec 5, 2019, 5:43:37 PM12/5/19
to LakshmiKanth Gupta, Protocol Buffers
I assume your converter is set up as a protoc plugin? In that case you can examine the descriptor for each field to see if it has a custom option defined or not. The details depend on the language you are using, though.

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LakshmiKanth Gupta

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Dec 5, 2019, 11:01:49 PM12/5/19
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Yes.I am developing protoc plugin using c++.But I didn't find any function to do that. Could somebody help me with that. Also couldn't find the information of the options.

I am using following code:

FieldOptions l_options= m_record->field(i)->options();

From here I couldn't figure out how I can look at these options.




On Thursday, December 5, 2019 at 11:43:37 PM UTC+1, Adam Cozzette wrote:
I assume your converter is set up as a protoc plugin? In that case you can examine the descriptor for each field to see if it has a custom option defined or not. The details depend on the language you are using, though.

On Thu, Dec 5, 2019 at 12:26 PM LakshmiKanth Gupta <klkv...@gmail.com> wrote:
Hi,

Currently I am writing a convertor from proto format to ttcn3 format.

Messages which I have defined has some custom Field options. How can I check whether a field has custom options or not.


syntax="proto3";
import "google/protobuf/descriptor.proto"
extend google.protobuf.FieldOptions{
   bool presence=50001;
}

message Mymessage
{
    int32 foo=1[(presence)=true];
    string bar=2;
}

This is my file. I would like to know when my convertor is invoked using protoc whether a field has options defined or not.

Thanks in advance,

with best regards,
  Gupta

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LakshmiKanth Gupta

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Dec 6, 2019, 8:33:25 AM12/6/19
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Finally I have figured out whether a field has options or not.

Unfortunately every field in message is associated with FieldOptions. By default, each field has DefaultOptions .So I could make pointer comparision and say whether a field has Custom field options or not.


Final question remains: How do I know the attributes of FieldOptions.

Adam Cozzette

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Dec 6, 2019, 1:26:22 PM12/6/19
to LakshmiKanth Gupta, Protocol Buffers

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Nadav Samet

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Dec 6, 2019, 1:31:00 PM12/6/19
to Adam Cozzette, LakshmiKanth Gupta, Protocol Buffers
KakshmiKanth, in addition, please take a look at HasExtension and GetExtension: https://developers.google.com/protocol-buffers/docs/reference/cpp-generated#extension to get your extension field from FieldOptions.

To view this discussion on the web visit https://groups.google.com/d/msgid/protobuf/CADqAXr57Eofka0-qr%3Dn4CkhqsY%2B6Qf8-Kvuugp5r4%2BE8TBGeXw%40mail.gmail.com.


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LakshmiKanth Gupta

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Dec 7, 2019, 12:19:15 PM12/7/19
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Here is way to do it without code generation. 

When we are developing compiler plugin....it is not feasible to use code generated c++.

I think the following solution works:
const Reflection *reflection= message.GetReflection();
std::vector<const FieldDescriptor *> l_fields;
reflection.ListFields( message, &fields );

Once we have FieldDescriptor, then it is usual business
 

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