Allow relay=false for light filter nodes (#518)

waku/v2/node/wakunode2.nim

@@ -180,6 +180,11 @@ proc stop*(node: WakuNode) {.async.} =
   node.started = false
 
 proc subscribe(node: WakuNode, topic: Topic, handler: Option[TopicHandler]) =
+  if node.wakuRelay.isNil:
+    error "Invalid API call to `subscribe`. WakuRelay not mounted."
+    # @TODO improved error handling
+    return
+
   info "subscribe", topic=topic
 
   proc defaultHandler(topic: string, data: seq[byte]) {.async, gcsafe.} =
@@ -242,6 +247,11 @@ proc unsubscribe*(node: WakuNode, topic: Topic, handler: TopicHandler) =
   ## Unsubscribes a handler from a PubSub topic.
   ##
   ## Status: Implemented.
+  if node.wakuRelay.isNil:
+    error "Invalid API call to `unsubscribe`. WakuRelay not mounted."
+    # @TODO improved error handling
+    return
+  
   info "unsubscribe", topic=topic
 
   let wakuRelay = node.wakuRelay
@@ -251,6 +261,12 @@ proc unsubscribeAll*(node: WakuNode, topic: Topic) =
   ## Unsubscribes all handlers registered on a specific PubSub topic.
   ##
   ## Status: Implemented.
+  
+  if node.wakuRelay.isNil:
+    error "Invalid API call to `unsubscribeAll`. WakuRelay not mounted."
+    # @TODO improved error handling
+    return
+  
   info "unsubscribeAll", topic=topic
 
   let wakuRelay = node.wakuRelay
@@ -280,6 +296,11 @@ proc publish*(node: WakuNode, topic: Topic, message: WakuMessage,  rlnRelayEnabl
   ##
   ## Status: Implemented.
   ## When rlnRelayEnabled is true, a zkp will be generated and attached to the message (it is an experimental feature)
+  
+  if node.wakuRelay.isNil:
+    error "Invalid API call to `publish`. WakuRelay not mounted. Try `lightpush` instead."
+    # @TODO improved error handling
+    return
 
   let wakuRelay = node.wakuRelay
   debug "publish", topic=topic, contentTopic=message.contentTopic
@@ -346,6 +367,20 @@ proc mountFilter*(node: WakuNode) =
       node.filters.notify(message, requestId) # Trigger filter handlers on a light node
       waku_node_messages.inc(labelValues = ["filter"])
 
+  if node.wakuRelay.isNil:
+    debug "light node: mounting relay without starting"
+    ## WakuFilter currently requires WakuRelay to be mounted in order to work.
+    ## This is to allow protocol stream negotation with full nodes to succeed.
+    ## Here we mount relay on the switch only, but do not subscribe to any pubsub
+    ## topics. We also never start the relay protocol.
+    ## @TODO: remove WakuRelay dependency
+    node.switch.mount(WakuRelay.init(
+      switch = node.switch,
+      triggerSelf = true,
+      sign = false,
+      verifySignature = false
+    ))
+
   node.wakuFilter = WakuFilter.init(node.peerManager, node.rng, filterHandler)
   node.switch.mount(node.wakuFilter)
   node.subscriptions.subscribe(WakuFilterCodec, node.wakuFilter.subscription())
@@ -654,13 +689,6 @@ when isMainModule:
     if conf.storenode != "":
       setStorePeer(node, conf.storenode)
 
-  # Filter setup
-  if (conf.filternode != "") or (conf.filter):
-    mountFilter(node)
-
-    if conf.filternode != "":
-      setFilterPeer(node, conf.filternode)
-
   # Relay setup
   if conf.relay:  # True by default
     mountRelay(node, conf.topics.split(" "), rlnRelayEnabled = conf.rlnrelay)
@@ -671,6 +699,13 @@ when isMainModule:
   # NOTE Must be mounted after relay
   if conf.lightpush:
     mountLightPush(node)
+  
+  # Filter setup. NOTE Must be mounted after relay
+  if (conf.filternode != "") or (conf.filter):
+    mountFilter(node)
+
+    if conf.filternode != "":
+      setFilterPeer(node, conf.filternode)
 
   if conf.rpc:
     startRpc(node, conf.rpcAddress, Port(conf.rpcPort + conf.portsShift), conf)