add doc for refactored from zero amount to amount less

lightning-invoice/src/payment.rs

@@ -25,10 +25,12 @@ use lightning::routing::router::{PaymentParameters, RouteParameters};
 ///
 /// Will always succeed unless the invoice has an amount specified, in which case
 /// [`payment_parameters_from_invoice`] should be used.
+/// An amount-less invoice, also known as a zero-amount invoice, refers to an invoice
+/// where the amount to be paid is zero. In this context, both terms are used synonymously.
 ///
 /// [`ChannelManager::send_payment`]: lightning::ln::channelmanager::ChannelManager::send_payment
 /// [`ChannelManager::send_preflight_probes`]: lightning::ln::channelmanager::ChannelManager::send_preflight_probes
-pub fn payment_parameters_from_amount_less_invoice(invoice: &Bolt11Invoice, amount_msat: u64)
+pub fn payment_parameters_from_amountless_invoice(invoice: &Bolt11Invoice, amount_msat: u64)
 -> Result<(PaymentHash, RecipientOnionFields, RouteParameters), ()> {
 	if invoice.amount_milli_satoshis().is_some() {
 		Err(())
@@ -120,7 +122,7 @@ mod tests {
 			})
 			.unwrap();
 
-		assert!(payment_parameters_from_amount_less_invoice(&invoice, 42).is_err());
+		assert!(payment_parameters_from_amountless_invoice(&invoice, 42).is_err());
 
 		let (hash, onion, params) = payment_parameters_from_invoice(&invoice).unwrap();
 		assert_eq!(&hash.0[..], &payment_hash[..]);
@@ -154,7 +156,7 @@ mod tests {
 
 		assert!(payment_parameters_from_invoice(&invoice).is_err());
 
-		let (hash, onion, params) = payment_parameters_from_amount_less_invoice(&invoice, 42).unwrap();
+		let (hash, onion, params) = payment_parameters_from_amountless_invoice(&invoice, 42).unwrap();
 		assert_eq!(&hash.0[..], &payment_hash[..]);
 		assert_eq!(onion.payment_secret, Some(PaymentSecret([0; 32])));
 		assert_eq!(params.final_value_msat, 42);