lightningd: include offer_id in invoice_creation notification

When a BOLT 12 invoice is created via createinvoice and is associated
with a local offer, include the offer_id in the invoice_creation event
notification. This allows plugins to determine which offer triggered
an invoice creation without having to call listinvoices for every
created invoice.

For bolt11 invoices and bolt12 invoices not associated with a local
offer, the field is omitted.

Fixes #8191

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

Author: vincenzopalazzo

doc/developers-guide/plugin-development/event-notifications.md

@@ -181,6 +181,19 @@ A notification for topic `invoice_creation` is sent every time an invoice is cre
 }
 ```
 
+If the invoice is associated with a BOLT 12 offer, an `offer_id` field will be present:
+
+```json
+{
+  "invoice_creation": {
+    "label": "unique-label-for-invoice",
+    "preimage": "0000000000000000000000000000000000000000000000000000000000000000",
+    "msat": 10000,
+    "offer_id": "b1d1062abc09790a68be83e4c257614a57978e4053a954bfee5909ed71e23e03"
+  }
+}
+```
+
 Before version `23.11` the `msat` field was a string with msat-suffix, e.g: `"10000msat"`.
 
 ### `warning`

lightningd/invoice.c

@@ -872,7 +872,7 @@ invoice_complete(struct invoice_info *info,
 	json_add_u64(response, "created_index", details->created_index);
 
 	notify_invoice_creation(info->cmd->ld, info->b11->msat,
-				&info->payment_preimage, info->label);
+				&info->payment_preimage, info->label, NULL);
 
 	if (warning_no_listincoming)
 		json_add_string(response, "warning_listincoming",
@@ -1725,7 +1725,7 @@ static struct command_result *json_createinvoice(struct command *cmd,
 				     NULL))
 			return fail_exists(cmd, label);
 
-		notify_invoice_creation(cmd->ld, b11->msat, preimage, label);
+		notify_invoice_creation(cmd->ld, b11->msat, preimage, label, NULL);
 	} else {
 		struct tlv_invoice *inv;
 		struct sha256 offer_id, *local_offer_id;
@@ -1822,7 +1822,7 @@ static struct command_result *json_createinvoice(struct command *cmd,
 				     local_offer_id))
 			return fail_exists(cmd, label);
 
-		notify_invoice_creation(cmd->ld, &msat,	preimage, label);
+		notify_invoice_creation(cmd->ld, &msat, preimage, label, local_offer_id);
 	}
 
 	response = json_stream_success(cmd);

lightningd/notification.c

@@ -221,26 +221,30 @@ void notify_invoice_payment(struct lightningd *ld,
 static void invoice_creation_notification_serialize(struct json_stream *stream,
 						    const struct amount_msat *amount,
 						    const struct preimage *preimage,
-						    const struct json_escape *label)
+						    const struct json_escape *label,
+						    const struct sha256 *offer_id)
 {
 	if (amount != NULL)
 		json_add_amount_msat(stream, "msat", *amount);
 
 	json_add_preimage(stream, "preimage", preimage);
 	json_add_escaped_string(stream, "label", label);
+	if (offer_id)
+		json_add_sha256(stream, "offer_id", offer_id);
 }
 
 REGISTER_NOTIFICATION(invoice_creation)
 
 void notify_invoice_creation(struct lightningd *ld,
 			     const struct amount_msat *amount,
 			     const struct preimage *preimage,
-			     const struct json_escape *label)
+			     const struct json_escape *label,
+			     const struct sha256 *offer_id)
 {
 	struct jsonrpc_notification *n = notify_start(ld, "invoice_creation");
 	if (!n)
 		return;
-	invoice_creation_notification_serialize(n->stream, amount, preimage, label);
+	invoice_creation_notification_serialize(n->stream, amount, preimage, label, offer_id);
 	notify_send(ld, n);
 }
 

lightningd/notification.h

@@ -42,7 +42,8 @@ void notify_invoice_payment(struct lightningd *ld,
 void notify_invoice_creation(struct lightningd *ld,
 			     const struct amount_msat *amount,
 			     const struct preimage *preimage,
-			     const struct json_escape *label);
+			     const struct json_escape *label,
+			     const struct sha256 *offer_id);
 
 void notify_channel_opened(struct lightningd *ld,
 			   const struct node_id *node_id,

lightningd/test/run-invoice-select-inchan.c

@@ -530,7 +530,8 @@ void notify_disconnect(struct lightningd *ld UNNEEDED, const struct node_id *nod
 void notify_invoice_creation(struct lightningd *ld UNNEEDED,
 			     const struct amount_msat *amount UNNEEDED,
 			     const struct preimage *preimage UNNEEDED,
-			     const struct json_escape *label UNNEEDED)
+			     const struct json_escape *label UNNEEDED,
+			     const struct sha256 *offer_id UNNEEDED)
 { fprintf(stderr, "notify_invoice_creation called!\n"); abort(); }
 /* Generated stub for notify_invoice_payment */
 void notify_invoice_payment(struct lightningd *ld UNNEEDED,