error_handling/
error_handling.rs

1//! Handling CEL evaluation errors.
2//!
3//! Run with: cargo run -p cel-core --example error_handling
4
5use cel_core::{CelType, Env, MapActivation, Value};
6
7fn main() {
8    let env = Env::with_standard_library()
9        .with_variable("x", CelType::Int)
10        .with_variable("items", CelType::list(CelType::Int));
11
12    let mut activation = MapActivation::new();
13
14    // Division by zero returns an error value
15    println!("=== Division by zero ===");
16    activation.insert("x", 0);
17    let ast = env.compile("10 / x").unwrap();
18    let program = env.program(&ast).unwrap();
19    let result = program.eval(&activation);
20
21    match &result {
22        Value::Error(err) => println!("Error: {}", err),
23        other => println!("Result: {}", other),
24    }
25
26    // Index out of bounds
27    println!("\n=== Index out of bounds ===");
28    activation.insert("items", Value::list([1, 2, 3]));
29    let ast = env.compile("items[10]").unwrap();
30    let program = env.program(&ast).unwrap();
31    let result = program.eval(&activation);
32
33    match &result {
34        Value::Error(err) => println!("Error: {}", err),
35        other => println!("Result: {}", other),
36    }
37
38    // Key not found in map
39    println!("\n=== Key not found ===");
40    let env = Env::with_standard_library()
41        .with_variable("config", CelType::map(CelType::String, CelType::String));
42    let mut activation = MapActivation::new();
43    activation.insert("config", Value::map([("host", "localhost")]));
44
45    let ast = env.compile("config.missing_key").unwrap();
46    let program = env.program(&ast).unwrap();
47    let result = program.eval(&activation);
48
49    match &result {
50        Value::Error(err) => println!("Error: {}", err),
51        other => println!("Result: {}", other),
52    }
53
54    // Use has() to safely check field existence
55    println!("\n=== Safe field access with has() ===");
56    let ast = env
57        .compile("has(config.missing_key) ? config.missing_key : 'default'")
58        .unwrap();
59    let program = env.program(&ast).unwrap();
60    let result = program.eval(&activation);
61    println!("Result: {}", result);
62}
error_handling/error_handling.rs

error_handling/
error_handling.rs
