Allow preprocess.send callbacks to request a line not be sent at all

src/IRCLine.py

@@ -46,12 +46,18 @@ class ParsedLine(object):
         self.args = IRCArgs(args)
         self.source = source
         self.tags = {} if tags == None else tags
+        self._valid = True
 
     def __repr__(self):
         return "ParsedLine(%s)" % self.__str__()
     def __str__(self):
         return self.format()
 
+    def valid(self) -> bool:
+        return self._valid
+    def invalidate(self):
+        self._valid = False
+
     def _tag_str(self, tags: typing.Dict[str, str]) -> str:
         tag_pieces = []
         for tag, value in tags.items():

src/IRCServer.py

@@ -256,7 +256,8 @@ class Server(IRCObject.Object):
             self.events.on("raw.send").call_unsafe(server=self,
                 line=line.parsed_line)
 
-    def send(self, line_parsed: IRCLine.ParsedLine, immediate: bool=False):
+    def send(self, line_parsed: IRCLine.ParsedLine, immediate: bool=False
+            ) -> typing.Optional[IRCLine.SentLine]:
         if not self.send_enabled:
             return None
 
@@ -267,6 +268,7 @@ class Server(IRCObject.Object):
         self.events.on("preprocess.send").call_unsafe(server=self,
             line=line_parsed, events=line_events)
 
+        if line_parsed.valid():
             line = line_parsed.format()
             line_obj = IRCLine.SentLine(line_events, datetime.datetime.utcnow(),
                 self.hostmask(), line_parsed)
@@ -276,6 +278,7 @@ class Server(IRCObject.Object):
                 self.bot.trigger_write()
 
             return line_obj
+        return None
     def send_raw(self, line: str):
         return self.send(utils.irc.parse_line(line))