Macro pack 

macro_rules! pack {
    ($($tt:tt)*) => { ... };
}

Creates a shmp::Pack value using a JSON-like syntax.

This macro provides an intuitive way to construct Pack enums, which is especially useful for creating complex, nested data structures for tests or dynamic configurations.

Syntax

• Literals: pack!(null), pack!(true), pack!(123), pack!(3.14), pack!("hello")
• Arrays: pack!([1, "two", false]).
• Maps (Objects): pack!({ "key": "value", "number": 123 }).
• Expressions: Any valid Rust expression can be used as a value. To avoid ambiguity with the map syntax pack!({ ... }), block expressions must be wrapped in parentheses (e.g., ({ let x = 1; x })) or use the dedicated pack!(block { ... }) syntax.

Examples

let data = pack!({
    "user_id": 1024,
    "username": "shmp_user",
    "tags": ["rust", "msgpack", "serde"],
    "config": { "retries": 3, "timeout": null }
});

assert_eq!(data["username"], pack!("shmp_user"));
assert_eq!(data["tags"][0], pack!("rust"));