rustapi-macros: The Magic

rustapi-macros reduces boilerplate by generating code at compile time.

#[debug_handler]

The most important macro for beginners. Rust’s error messages for complex generic traits (like Handler) can be notoriously difficult to understand.

If your handler doesn’t implement the Handler trait (e.g., because you used an argument that isn’t a valid Extractor), the compiler might give you an error spanning the entire RustApi::new() chain, miles away from the actual problem.

#[debug_handler] fixes this.

It verifies the handler function in isolation and produces clear error messages pointing exactly to the invalid argument.

#![allow(unused)]
fn main() {
#[debug_handler]
async fn handler(
    // Compile Error: "String" does not implement FromRequest. 
    // Did you mean "Json<String>" or "Body"?
    body: String 
) { ... }
}

#[derive(FromRequest)]

Automatically implement FromRequest for your structs.

#![allow(unused)]
fn main() {
#[derive(FromRequest)]
struct MyExtractor {
    // These fields must themselves be Extractors
    header: HeaderMap,
    body: Json<MyData>,
}

// Now you can use it in a handler
async fn handler(input: MyExtractor) {
    println!("{:?}", input.header);
}
}

This is heavily used to group multiple extractors into a single struct (often called the “Parameter Object” pattern), keeping function signatures clean.