json-rpc: Add failcode info in listforwards

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - JSON API: new plugin `invoice_payment` hook for intercepting invoices before they're paid.
 - plugin: the `connected` hook can now send an `error_message` to the rejected peer.
 - Protocol: we now enforce `option_upfront_shutdown_script` if a peer negotiates it.
+- JSON API: `listforwards` now includes the local_failed forwards with failcode (Issue [#2435](https://github.com/ElementsProject/lightning/issues/2435), PR [#2524](https://github.com/ElementsProject/lightning/pull/2524))
 
 ### Changed
 

lightningd/peer_htlcs.c

@@ -1915,6 +1915,12 @@ static void listforwardings_add_forwardings(struct json_stream *response, struct
 				     "fee", "fee_msat");
 		json_add_string(response, "status", forward_status_name(cur->status));
 
+		if(cur->failcode != 0) {
+			json_add_num(response, "failcode", cur->failcode);
+			json_add_string(response, "failreason",
+					 onion_type_name(cur->failcode));
+		}
+
 #ifdef COMPAT_V070
 		/* If a forwarding doesn't have received_time it was created
 		 * before we added the tracking, do not include it here. */