await server.send() should block until it hits the wire

ircrobots/interface.py

@@ -1,3 +1,4 @@
+from asyncio import Future
 from typing  import Awaitable, Iterable, List, Optional
 from enum    import IntEnum
 
@@ -13,11 +14,12 @@ class SendPriority(IntEnum):
     LOW    = 20
     DEFAULT = MEDIUM
 
-class PriorityLine(object):
+class SentLine(object):
     def __init__(self, priority: int, line: Line):
         self.priority       = priority
         self.line           = line
-    def __lt__(self, other: "PriorityLine") -> bool:
+        self.future: Future = Future()
+    def __lt__(self, other: "SentLine") -> bool:
         return self.priority < other.priority
 
 class ICapability(object):

ircrobots/server.py

@@ -8,7 +8,7 @@ from ircstates        import Emit
 from irctokens        import build, Line, tokenise
 
 from .ircv3     import CAPContext, CAPS, CAP_SASL
-from .interface import (ConnectionParams, ICapability, IServer, PriorityLine,
+from .interface import (ConnectionParams, ICapability, IServer, SentLine,
     SendPriority)
 from .matching  import BaseResponse
 from .sasl      import SASLContext, SASLResult
@@ -29,7 +29,7 @@ class Server(IServer):
             rate_limit=THROTTLE_RATE, period=THROTTLE_TIME)
         self.sasl_state = SASLResult.NONE
 
-        self._write_queue: PriorityQueue[PriorityLine] = PriorityQueue()
+        self._write_queue: PriorityQueue[SentLine] = PriorityQueue()
         self._cap_queue:   Set[ICapability] = set([])
 
         self._wait_for: List[Tuple[BaseResponse, Future]] = []
@@ -37,7 +37,9 @@ class Server(IServer):
     async def send_raw(self, line: str, priority=SendPriority.DEFAULT):
         await self.send(tokenise(line), priority)
     async def send(self, line: Line, priority=SendPriority.DEFAULT):
-        await self._write_queue.put(PriorityLine(priority, line))
+        prio_line = SentLine(priority, line)
+        await self._write_queue.put(prio_line)
+        await prio_line.future
 
     def set_throttle(self, rate: int, time: float):
         self.throttle.rate_limit = rate
@@ -100,18 +102,24 @@ class Server(IServer):
     async def line_written(self, line: Line):
         pass
     async def _write_lines(self) -> List[Line]:
-        lines: List[Line] = []
+        lines: List[SentLine] = []
 
         while (not lines or
                 (len(lines) < 5 and self._write_queue.qsize() > 0)):
             prio_line = await self._write_queue.get()
-            lines.append(prio_line.line)
+            lines.append(prio_line)
 
         for line in lines:
             async with self.throttle:
-                self._writer.write(f"{line.format()}\r\n".encode("utf8"))
+                self._writer.write(
+                    f"{line.line.format()}\r\n".encode("utf8"))
+
         await self._writer.drain()
-        return lines
+
+        for line in lines:
+            line.future.set_result(None)
+
+        return [l.line for l in lines]
 
     # CAP-related
     async def queue_capability(self, cap: ICapability):