Macro message 

macro_rules! message {
    (data = $data:tt, $($arg:tt)*) => { ... };
    ($($arg:tt)*) => { ... };
}

Emit an R message from Rust with rust_message class layering.

Rides the tagged-condition transport that every #[miniextendr] function uses. The raised condition has class c("rust_message", "simpleMessage", "message", "condition"). Muffled by suppressMessages() automatically (standard R restart mechanism).

An optional data = ... form (before the message) attaches named fields readable as m$<name> in withCallingHandlers — same grammar and supported value types as crate::error! (see there for details). There is no class = form for message!.

See also

• crate::warning! / crate::condition! — louder/quieter sibling kinds.
• crate::error! — for fatal failures.
• std::panic! — escape hatch.
• crate::error_value — tagged-SEXP transport rationale.

No name-collision caveat: there is no pub mod message, so use miniextendr_api::message; then message!(...) works directly.

Example

use miniextendr_api::message;

#[miniextendr]
fn log_step(step: i32) {
    message!("step {} complete", step);
}

log_step(3L)
# step 3 complete

suppressMessages(log_step(3L))  # no output