Minor fixes

SpiderMQTT.py

@@ -224,7 +224,17 @@ class Message:
         return out
 
   def __str__(self):
-    return 'Message[topic=\'{}\' payload=\'{}\']'.format(self.topic, self.str(default='<binary garbage>'))
+
+    txtLen = 30
+
+    txt = self.str(default='<binary garbage>')
+    if len(txt) > txtLen:
+      txt = txt[ 0 : txtLen-2 ] + '…'
+
+    return 'Message[topic=\'{}\' payload=\'{}\']'.format(self.topic, txt)
+
+  def __repr__(self) -> str:
+    return self.__str__()
 
 
 if False:
@@ -328,12 +338,13 @@ class Subscription:
         self.state = self.CLEANUP
         self.__unsub()
 
-  def addSubscribeCallbacks(self, callback: Callable[[Message], None]) -> None:
-    self.subscribeCallbacks.add(callback)
-    if self.state is self.ACTIVE:
-      Executor(callback)
+  def addSubscribeCallback(self, callback: Callable[[Message], None]) -> None:
+    if callback is not None:
+      self.subscribeCallbacks.add(callback)
+      if self.state is self.ACTIVE:
+        Executor(callback)
 
-  def removeSubscribeCallbacks(self, callback: Callable[[Message], None]) -> None:
+  def removeSubscribeCallback(self, callback: Callable[[Message], None]) -> None:
     if callback in self.subscribeCallbacks:
       self.subscribeCallbacks.remove(callback)
 
@@ -487,7 +498,7 @@ class SpiderMQTT:
   def addCallback(self, topic: str, callback: Callable[[Message], None], subscribeCallback=None) -> None:
     if topic in self.subscriptions:
       self.subscriptions[topic].addCallback(callback)
-      self.subscriptions[topic].addSubscribeCallback(callback)
+      self.subscriptions[topic].addSubscribeCallback(subscribeCallback)
     else:
       self.subscriptions[topic] = Subscription(self, topic, callback, subscribeCallback)