[Feature Request] Bitwise operation support in predefined CEL

[KeXiangWang]

Feature description:
Support bitwise operations in predefined CEL rules.

For example,

extend buf.validate.Int32Rules {
  optional bool power_of_two = 100000 [(buf.validate.predefined).cel = {
    id: "int32.power_of_two"
    message: "value must be a power of two"
    expression: "this >= 0 && (this & (this - 1)) == 0"
  }];
}

although the above rules can be successfully complied by protoc, when execute, I got this error:

compilation error: failed to compile standard rule "xxxxx.power_of_two": compilation error: failed to compile expression int32.power_of_two: ERROR: <input>:1:20: Syntax error: token recognition error at: '& '
 | this >= 0 && (this & (this - 1)) == 0

I think CEL itself support bitwise operations? I'm not sure whether protovalidate disable it or there's some reason it doesn't work.

My toolchain version:
protoc: libprotoc 3.21.9
validate.proto: https://github.com/bufbuild/protovalidate/blob/51ee9b3a85ed11c19a2b8023aa2520cca82f431e/proto/protovalidate/buf/validate/validate.proto
protovalidate-go: buf.build/gen/go/bufbuild/protovalidate/protocolbuffers/go v1.36.6-20250425153114-8976f5be98c1.1

Problem it solves or use case:
When predefining some more complicated rules.

Proposed implementation or solution:
Sorry, I'm still not familiar with the implementation yet.

Contribution:
Will to contribute, if I can get necessary guidance.

Examples or references:
None

Additional context:
None

[KeXiangWang]

Oh, sorry. I just checked the cel-spec repo. Looks like bitwise operations have not been implement on their side. google/cel-spec#286. When they support them, protovalidate only need to followup the updates.

[KeXiangWang]

However, the cel-go has already implemented the bitwise operations. https://github.com/google/cel-go/blob/f6d3c92171c2c8732a8d0a4b24d6729df4261520/ext/math.go#L95 Is it possible for protovalidate-go support bitwise operations as well?

[smaye81]

Hi, @KeXiangWang. We're trying to both follow the spec and keep our implementations consistent, so we'd rather not deviate quite yet if we don't have to. That being said, this is a fair request for when it gets added to the spec. Would you mind creating an issue for adding this on the protovalidate-go repo?

[KeXiangWang]

We're trying to both follow the spec and keep our implementations consistent, so we'd rather not deviate quite yet if we don't have to.

Understood. Thanks!
I took a look yesterday of your implementation for these kind of extension, which seems not too non-trivial. If I can help implement the ext/math for protovalidate-go and submit a PR to the repo, would you consider merging it into main branch?

[KeXiangWang]

I've copied most of the information of this issue to bufbuild/protovalidate-go#246. Feel free to close this issue if you think it's inappropriate to be here.

[smaye81]

If I can help implement the ext/math for protovalidate-go and submit a PR to the repo, would you consider merging it into main branch?

Sure. Appreciate the interest. 👍

[nicksnyder]

Just to clarify, we can't support this feature (or any feature) until/unless:

1. The CEL spec itself supports the feature, and
2. We have PRs ready to add support for the feature to all protovalidate implementations

We need to maintain consistency across all Protovalidate implementations.

[KeXiangWang]

Understood. NP