Error when quantity set without amount in bolt12_receive

Previously, setting quantity without amount_msat silently produced a
variable-amount offer with no quantity constraint. Now both the server
and CLI reject this misconfiguration with a clear error message.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: benthecarman

ldk-server-cli/src/main.rs

@@ -780,6 +780,11 @@ async fn main() {
 			);
 		},
 		Commands::Bolt12Receive { description, amount, expiry_secs, quantity } => {
+			if quantity.is_some() && amount.is_none() {
+				handle_error_msg(
+					"quantity can only be set for fixed-amount offers (amount must be provided)",
+				);
+			}
 			let amount_msat = amount.map(|a| a.to_msat());
 			handle_response_result::<_, Bolt12ReceiveResponse>(
 				client

ldk-server/src/api/bolt12_receive.rs

@@ -11,23 +11,29 @@ use hex::DisplayHex;
 use ldk_server_protos::api::{Bolt12ReceiveRequest, Bolt12ReceiveResponse};
 
 use crate::api::error::LdkServerError;
+use crate::api::error::LdkServerErrorCode::InvalidRequestError;
 use crate::service::Context;
 
 pub(crate) fn handle_bolt12_receive_request(
 	context: Context, request: Bolt12ReceiveRequest,
 ) -> Result<Bolt12ReceiveResponse, LdkServerError> {
-	let offer = match request.amount_msat {
-		Some(amount_msat) => context.node.bolt12_payment().receive(
-			amount_msat,
-			&request.description,
-			request.expiry_secs,
-			request.quantity,
-		)?,
-		None => context
-			.node
-			.bolt12_payment()
-			.receive_variable_amount(&request.description, request.expiry_secs)?,
-	};
+	let offer =
+		match (request.amount_msat, request.quantity) {
+			(Some(amount_msat), quantity) => context.node.bolt12_payment().receive(
+				amount_msat,
+				&request.description,
+				request.expiry_secs,
+				quantity,
+			)?,
+			(None, Some(_)) => return Err(LdkServerError::new(
+				InvalidRequestError,
+				"quantity can only be set for fixed-amount offers (amount_msat must be provided)",
+			)),
+			(None, None) => context
+				.node
+				.bolt12_payment()
+				.receive_variable_amount(&request.description, request.expiry_secs)?,
+		};
 
 	let offer_id = offer.id().0.to_lower_hex_string();
 	let response = Bolt12ReceiveResponse { offer: offer.to_string(), offer_id };