Generate appropriate `oneof` validation in JSON Schema

[hudlow]

Per #94 and #108, it looks like there's strong demand for improved validation around protobuf oneof.

[hudlow]

@boekkooi-impossiblecloud and @Prastiwar, thanks much to both of you for investing the time into proposed implementations!

I've been asked to work through the options here, and I'd be curious to know how you're using generated JSON Schemas in your architecture. In particular:

• Are you using them to do anything beyond validation (e.g., code generation, or docs generation)?
• Are you using protovalidate rules in the source protos?
• Are you using them in conjunction with a protovalidate implementation?

If you want to chat about any of this feel free to reach out to me on the Buf Slack.

[boekkooi-impossiblecloud]

Hey @hudlow

Thanks for looking into this.

Are you using them to do anything beyond validation (e.g., code generation, or docs generation)?

Yes, we actually don't use this library for validation ourself. Our use case is primarily to provide the schema's to our partners and/or use them in our OpenAPI v3 definition (aka as documentation).
However, our partners may use these JSON schema's to generate API clients or do client side validation.

Are you using protovalidate rules in the source protos?

Yes

Are you using them in conjunction with a protovalidate implementation?

I'm not 100% sure what you mean by this. In our implementation for handling JSON we use a custom set of Transcoders (generated from the protobuf definitions) that transform the JSON into protobuf (similar to grpc-gateway but with generated code and more strict). After this we validate the protobuf message using buf.build/go/protovalidate and passed it onward.

Please let me know if you have any more questions (or possibly ideas).

P.S. we currently only provide a JSON API to our clients and no GRPC directly.

[Prastiwar]

Are you using them to do anything beyond validation (e.g., code generation, or docs generation)?

Our primary use case is to autogenerate a form modal on frontend. There are rather no existing libraries for this job directly using proto, but it's much more common to generate the forms based on the jsonschema. We don't want to use protobufjs or gRPC for that purpose, since we'll be handling multiple form versions simultaneously.

Are you using protovalidate rules in the source protos?
Are you using them in conjunction with a protovalidate implementation?

We don't use the protovalidate at the moment (POC), but it's likely that we'll use it at some point on proto and go implementation.

[boekkooi-impossiblecloud]

Hey @hudlow

Happy new year! I was wondering is there any news on this topic or any way I could help move this forward?

Thanks in advance!

[jlumsden-mts]

We're also interested in this having just realised that oneof is not covered by the current implementation. It would seem to me that mapping directly to JSON schema oneOf would be the clearest but is the issue that we have "at most one" in proto and "exactly one" in JSON schema?