Attribute Macro attribute 

#[attribute]

Defines an attribute macro entry point that auto-parses the annotated item into typed inputs.

Extractors marked #[zyn(input)] are resolved from the annotated item via FromInput. An optional args: zyn::Args parameter receives the raw attribute arguments. The macro name defaults to the function name.

Examples

// In your proc-macro crate (lib.rs):
#[zyn::attribute]
fn log_call(
    #[zyn(input)] item: syn::ItemFn,
    args: zyn::Args,
) -> zyn::TokenStream {
    let prefix = args.get("prefix")
        .and_then(|a| a.value::<String>().ok())
        .unwrap_or_else(|| "CALL".into());
    zyn::zyn! {
        {{ item }}
    }
}

// Applied to a function:
#[log_call(prefix = "DEBUG")]
fn my_fn() { ... }

With an explicit macro name:

#[zyn::attribute("trace")]
fn trace_impl(#[zyn(input)] item: syn::ItemFn) -> zyn::TokenStream { ... }
// Registers as #[trace]

Debugging

Add debug to inspect the generated code as a compiler note diagnostic. Requires the ZYN_DEBUG environment variable to match the function name (supports * wildcards).

#[zyn::attribute(debug)]
#[zyn::attribute(debug = "pretty")]  // requires `pretty` feature

Without ZYN_DEBUG, the debug argument is inert — safe to leave in source. See the debugging guide for details.