don't return nil in dial (#205)

* dont return nil in dial

* don't crash on pubsub send

libp2p.nimble

@@ -14,7 +14,7 @@ requires "nim >= 1.2.0",
          "chronos >= 2.3.8",
          "metrics",
          "secp256k1",
-         "stew"
+         "stew >= 0.1.0"
 
 proc runTest(filename: string, verify: bool = true, sign: bool = true) =
   var excstr: string = "nim c -r --opt:speed -d:debug --verbosity:0 --hints:off"

libp2p/protocols/pubsub/pubsubpeer.nim

@@ -48,6 +48,7 @@ proc isConnected*(p: PubSubPeer): bool =
 
 proc `conn=`*(p: PubSubPeer, conn: Connection) =
   trace "attaching send connection for peer", peer = p.id
+  if not(isNil(conn)):
     p.sendConn = conn
     p.onConnect.fire()
 
@@ -113,6 +114,7 @@ proc send*(p: PubSubPeer, msgs: seq[RPCMsg]) {.async.} =
         trace "about to send message", peer = p.id,
                                        encoded = digest
         await p.onConnect.wait()
+        if p.isConnected: # this can happen if the remote disconnected
           trace "sending encoded msgs to peer", peer = p.id,
                                                 encoded = encoded.buffer.shortLog
           await p.sendConn.writeLp(encoded.buffer)

libp2p/switch.nim

@@ -282,8 +282,7 @@ proc dial*(s: Switch,
     trace "Attempting to select remote", proto = proto
 
   if not await s.ms.select(result, proto):
-    warn "Unable to select sub-protocol", proto = proto
-    return nil
+    raise newException(CatchableError, "Unable to select sub-protocol " & proto)
 
 proc mount*[T: LPProtocol](s: Switch, proto: T) {.gcsafe.} =
   if isNil(proto.handler):