lightningd: add short_channel_id option to listpeerchannels.

Requested-by: @whitslack
Closes: #8233
Changelog-Added: JSON-RPC: `listpeerchannels` now has a `short_channel_id` parameter for just listing a specific channel.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Author: rustyrussell

.msggen.json

@@ -2781,7 +2781,8 @@
             "ListPeerChannels.channels[].updates.remote.htlc_minimum_msat": 1
         },
         "ListpeerchannelsRequest": {
-            "ListPeerChannels.id": 1
+            "ListPeerChannels.id": 1,
+            "ListPeerChannels.short_channel_id": 2
         },
         "ListpeerchannelsResponse": {
             "ListPeerChannels.channels[]": 1
@@ -10338,6 +10339,10 @@
             "added": "v23.02",
             "deprecated": null
         },
+        "ListPeerChannels.short_channel_id": {
+            "added": "v25.05",
+            "deprecated": null
+        },
         "ListPeers": {
             "added": "pre-v0.10.1",
             "deprecated": null

cln-grpc/proto/node.proto

@@ -23126,6 +23126,13 @@
             "description": [
               "If supplied, limits the channels to just the peer with the given ID, if it exists."
             ]
+          },
+          "short_channel_id": {
+            "added": "v25.05",
+            "type": "short_channel_id",
+            "description": [
+              "If supplied, limits the channels to just this short_channel_id (or local alias), if it exists.  Cannot be used with 'id'."
+            ]
           }
         }
       },

cln-grpc/src/convert.rs

@@ -1008,13 +1008,15 @@ def listpeers(self, peerid=None, level=None):
         }
         return self.call("listpeers", payload)
 
-    def listpeerchannels(self, peer_id=None):
+    def listpeerchannels(self, peer_id=None, short_channel_id=None):
         """
         Show current peers channels, and if the {peer_id} is specified
-        all the channels for the peer are returned.
+        all the channels for the peer are returned, and if {short_channel_id} is
+        specified only that channel is returned.
         """
         payload = {
             "id": peer_id,
+            "short_channel_id": short_channel_id,
         }
         return self.call("listpeerchannels", payload)
 

cln-rpc/src/model.rs

@@ -21,6 +21,13 @@
         "description": [
           "If supplied, limits the channels to just the peer with the given ID, if it exists."
         ]
+      },
+      "short_channel_id": {
+        "added": "v25.05",
+        "type": "short_channel_id",
+        "description": [
+          "If supplied, limits the channels to just this short_channel_id (or local alias), if it exists.  Cannot be used with 'id'."
+        ]
       }
     }
   },

contrib/msggen/msggen/schema.json

@@ -2465,20 +2465,29 @@ static struct command_result *json_listpeerchannels(struct command *cmd,
 	struct node_id *peer_id;
 	struct peer *peer;
 	struct json_stream *response;
+	struct short_channel_id *scid;
 
-	/* FIME: filter by status */
-	if (!param(cmd, buffer, params,
-		   p_opt("id", param_node_id, &peer_id),
-		   NULL))
+	if (!param_check(cmd, buffer, params,
+			 p_opt("id", param_node_id, &peer_id),
+			 p_opt("short_channel_id", param_short_channel_id, &scid),
+			 NULL))
 		return command_param_failed();
 
+	if (scid && peer_id)
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "Cannot specify both short_channel_id and id");
+
 	response = json_stream_success(cmd);
 	json_array_start(response, "channels");
 
 	if (peer_id) {
 		peer = peer_by_id(cmd->ld, peer_id);
 		if (peer)
 			json_add_peerchannels(cmd, response, peer);
+	} else if (scid) {
+		const struct channel *c = any_channel_by_scid(cmd->ld, *scid, true);
+		if (c)
+			json_add_channel(cmd, response, NULL, c, c->peer);
 	} else {
 		struct peer_node_id_map_iter it;
 

contrib/pyln-client/pyln/client/lightning.py

@@ -4780,3 +4780,16 @@ def test_private_channel_no_reconnect(node_factory):
     wait_for(lambda: only_one(l3.rpc.listpeers()['peers'])['connected'] is True)
 
     assert only_one(l1.rpc.listpeers()['peers'])['connected'] is False
+
+
+def test_listpeerchannels_by_scid(node_factory):
+    l1, l2, l3 = node_factory.line_graph(3, announce_channels=False)
+
+    chans = l2.rpc.listpeerchannels(l1.info['id'])
+    c = only_one(chans['channels'])
+    assert l2.rpc.listpeerchannels(short_channel_id=c['short_channel_id']) == chans
+    assert l2.rpc.listpeerchannels(short_channel_id=c['alias']['local']) == chans
+    assert l2.rpc.listpeerchannels(short_channel_id=c['alias']['remote']) == {'channels': []}
+
+    with pytest.raises(RpcError, match="Cannot specify both short_channel_id and id"):
+        l2.rpc.listpeerchannels(peer_id=l1.info['id'], short_channel_id='1x2x3')