[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. 👍