Don't crash when acknowledging a cancelled ping.

Fix #1566.

src/websockets/asyncio/connection.py

@@ -750,7 +750,8 @@ def acknowledge_pings(self, data: bytes) -> None:
         for ping_id, (pong_waiter, ping_timestamp) in self.pong_waiters.items():
             ping_ids.append(ping_id)
             latency = pong_timestamp - ping_timestamp
-            pong_waiter.set_result(latency)
+            if not pong_waiter.done():
+                pong_waiter.set_result(latency)
             if ping_id == data:
                 self.latency = latency
                 break

tests/asyncio/test_connection.py

@@ -892,6 +892,15 @@ async def test_acknowledge_ping(self):
         async with asyncio_timeout(MS):
             await pong_waiter
 
+    async def test_acknowledge_canceled_ping(self):
+        """ping is acknowledged by a pong with the same payload after being canceled."""
+        async with self.drop_frames_rcvd():  # drop automatic response to ping
+            pong_waiter = await self.connection.ping("this")
+        pong_waiter.cancel()
+        await self.remote_connection.pong("this")
+        with self.assertRaises(asyncio.CancelledError):
+            await pong_waiter
+
     async def test_acknowledge_ping_non_matching_pong(self):
         """ping isn't acknowledged by a pong with a different payload."""
         async with self.drop_frames_rcvd():  # drop automatic response to ping
@@ -902,14 +911,26 @@ async def test_acknowledge_ping_non_matching_pong(self):
                 await pong_waiter
 
     async def test_acknowledge_previous_ping(self):
-        """ping is acknowledged by a pong with the same payload as a later ping."""
+        """ping is acknowledged by a pong for a later ping."""
         async with self.drop_frames_rcvd():  # drop automatic response to ping
             pong_waiter = await self.connection.ping("this")
             await self.connection.ping("that")
         await self.remote_connection.pong("that")
         async with asyncio_timeout(MS):
             await pong_waiter
 
+    async def test_acknowledge_previous_canceled_ping(self):
+        """ping is acknowledged by a pong for a later ping after being canceled."""
+        async with self.drop_frames_rcvd():  # drop automatic response to ping
+            pong_waiter = await self.connection.ping("this")
+            pong_waiter_2 = await self.connection.ping("that")
+        pong_waiter.cancel()
+        await self.remote_connection.pong("that")
+        async with asyncio_timeout(MS):
+            await pong_waiter_2
+        with self.assertRaises(asyncio.CancelledError):
+            await pong_waiter
+
     async def test_ping_duplicate_payload(self):
         """ping rejects the same payload until receiving the pong."""
         async with self.drop_frames_rcvd():  # drop automatic response to ping

tests/sync/test_connection.py

@@ -678,7 +678,7 @@ def test_acknowledge_ping_non_matching_pong(self):
         self.assertFalse(pong_waiter.wait(MS))
 
     def test_acknowledge_previous_ping(self):
-        """ping is acknowledged by a pong with the same payload as a later ping."""
+        """ping is acknowledged by a pong for as a later ping."""
         with self.drop_frames_rcvd():  # drop automatic response to ping
             pong_waiter = self.connection.ping("this")
             self.connection.ping("that")