Macro propagate_if_error 

macro_rules! propagate_if_error {
    (($($id:ident),*), $outputs:ident, continue) => { ... };
    ($result:expr, $outputs:ident, continue) => { ... };
    ($result:expr,$outputs:ident, break) => { ... };
    ($result:expr,$outputs:ident, return $rv:expr) => { ... };
}

Unwrap a Result value to its Result::Ok value or propagate the error to the downstream inputs and short circuit the logic.

Takes a Result value, a generated component’s Outputs, and an action to perform on error (break, continue, or return expr).

If the Result is Ok, the Result::Ok value is returned.

If the Result is Err, the error is propagated to the passed outputs, and the logic is short circuited with the passed action.

Example

let results: Vec<Result<i32, ()>> = vec![Ok(1),Err(()),Ok(2)];
while let Some(result) = results.next() {
  let value = propagate_if_error!(result, outputs, continue);
  println!("{}", value);
}