message_expression/
message_expression.rs

1//! Dynamic validation messages with `messageExpression`.
2//!
3//! A CRD validation rule can carry a `messageExpression` — a CEL expression that
4//! produces the failure message at evaluation time, so the message can embed the
5//! offending value (mirroring the apiserver's `messageExpression` support). When
6//! present and it evaluates to a string, kube-cel uses it; otherwise it falls back
7//! to the static `message`.
8//!
9//! Run with: `cargo run --example message_expression --features validation`
10
11use kube_cel::Validator;
12use serde_json::json;
13
14fn main() {
15    let schema = json!({
16        "type": "object",
17        "properties": {
18            "spec": {
19                "type": "object",
20                "properties": {
21                    "replicas": {"type": "integer"}
22                },
23                "x-kubernetes-validations": [{
24                    "rule": "self.replicas <= 5",
25                    // Static fallback, used if messageExpression is absent/non-string.
26                    "message": "too many replicas",
27                    // Dynamic message: embeds the actual value and the limit.
28                    "messageExpression":
29                        "'requested ' + string(self.replicas) + ' replicas, max allowed is 5'"
30                }]
31            }
32        }
33    });
34
35    let validator = Validator::new();
36
37    // Two invalid objects: the dynamic message differs per object.
38    for replicas in [8, 20] {
39        let object = json!({"spec": {"replicas": replicas}});
40        if let Err(errors) = validator.validate(&schema, &object, None) {
41            for err in &errors {
42                // Note the message reflects this object's value, not a fixed string.
43                println!("replicas={replicas}: {}", err.message);
44            }
45        }
46    }
47
48    // A valid object produces no errors (and so no message at all).
49    let ok = json!({"spec": {"replicas": 3}});
50    match validator.validate(&schema, &ok, None) {
51        Ok(()) => println!("replicas=3: 0 error(s)"),
52        Err(errors) => println!("replicas=3: {} error(s)", errors.len()),
53    }
54}
message_expression/message_expression.rs

message_expression/
message_expression.rs
