RsCel is a CEL evaluator written in Rust. CEL is a Turing-incomplete language that can be used to evaluate a user-provided expression. The language specification can be found here.
The design goals of this project are as follows:
- Isolated execution of CEL expressions
- Flexible enough to allow for a user to bend the spec if needed
- Can be used as a WASM depenedency (or other FFI)
The basic example of how to use:
use rscel::{CelContext, BindContext};
let mut ctx = CelContext::new();
let mut exec_ctx = BindContext::new();
ctx.add_program_str("main", "foo + 3").unwrap();
exec_ctx.bind_param("foo", 3.into()); // convert to CelValue
let res = ctx.exec("main", &exec_ctx).unwrap(); // CelValue::Int(6)
assert_eq!(res, 6.into());As of 0.10.0, binding protobuf messages from the protobuf crate is now available! Given the following protobuf message:
message Point {
int32 x = 1;
int32 y = 2;
}
The following code can be used to evaluate a CEL expression on a Point message:
use rscel::{CelContext, BindContext};
// currently rscel requires protobuf messages to be in a box
let p = Box::new(protos::Point::new());
p.x = 4;
p.y = 5;
let mut ctx = CelContext::new();
let mut exec_ctx = BindContext::new();
ctx.add_program_str("main", "p.x + 3").unwrap();
exec_ctx.bind_protobuf_msg("p", p);
assert_eq!(ctx.exec("main", &exec_ctx), 7.into());