Code generation for protovalidate

[fenollp]

From https://github.com/bufbuild/protoc-gen-validate the newer impl seems to now be https://github.com/bufbuild/protovalidate

[Adphi]

Hello @fenollp !

Thank you for bringing this up.

We’re fully aware of the newer implementation.
As noted in the rust support issue, the new version relies heavily on protobuf reflection and CEL expressions.

At the moment, we’re not planning to prioritize work on supporting or migrating to this approach.

[fenollp]

Hey thanks for taking the time :)

How is protovalidate requiring reflection? As I understand it and apart from the CEL features, this "new gen" impl is exactly the same, no?

[Adphi]

The key difference with the new approach (as seen in the Go implementation of protovalidate) is that there’s no more code generation. Instead of generating static validation code for each message type, all validation logic is handled at runtime by evaluating CEL expressions using protobuf reflection.

[fenollp]

From what I can gather the Go impl picking reflection was only a choice. I don't see a characteristic of the spec (not even https://buf.build/docs/protovalidate/schemas/custom-rules/#combining-message-rules nor simply using CEL) that would mandate the use of reflection.

If you know of specific features of protovalidate that even seem to make code generation impossible, I am interested.

I have code in vtprotobuf that's explicitly de-reflect'ed for the purpose of speed. IMO Google's gRPC team used reflection so that newer Golang features wouldn't change the "generated code" and thus save them CI build time / cache invalidation / space.

I'd like to have a go at this (when I have the timeTM) and maybe prove myself wrong :)

[Adphi]

The contributing guidelines state that a CEL interpreter is required. I guess that means it has to be interpreted.

[fenollp]

Well that's the same idea as embedding a uuid validator or a regexp checker isn't it :)

[fenollp]

From https://buf.build/docs/migration-guides/migrate-from-protoc-gen-validate/

performs all validations using reflection, so there's no protoc plugin to use or manage, and it doesn't require any code generation. You don't need the protoc-gen-validate plugin

So there it is: reflection is a "developer UX improvement", not a requirement driven by the functionality protovalidate actually provides.