Support recv() after the connection is closed.

Fix #1538.

docs/project/changelog.rst

@@ -34,6 +34,13 @@ notice.
 
 .. _14.0:
 
+Bug fixes
+.........
+
+* Once the connection is closed, messages previously received and buffered can
+  be read in the :mod:`asyncio` and :mod:`threading` implementations, just like
+  in the legacy implementation.
+
 14.0
 ----
 

src/websockets/asyncio/messages.py

@@ -40,9 +40,11 @@ def put(self, item: T) -> None:
         if self.get_waiter is not None and not self.get_waiter.done():
             self.get_waiter.set_result(None)
 
-    async def get(self) -> T:
+    async def get(self, block: bool = True) -> T:
         """Remove and return an item from the queue, waiting if necessary."""
         if not self.queue:
+            if not block:
+                raise EOFError("stream of frames ended")
             assert self.get_waiter is None, "cannot call get() concurrently"
             self.get_waiter = self.loop.create_future()
             try:
@@ -133,20 +135,16 @@ async def get(self, decode: bool | None = None) -> Data:
                 :meth:`get_iter` concurrently.
 
         """
-        if self.closed:
-            raise EOFError("stream of frames ended")
-
         if self.get_in_progress:
             raise ConcurrencyError("get() or get_iter() is already running")
-
         self.get_in_progress = True
 
         # Locking with get_in_progress prevents concurrent execution
         # until get() fetches a complete message or is cancelled.
 
         try:
             # First frame
-            frame = await self.frames.get()
+            frame = await self.frames.get(not self.closed)
             self.maybe_resume()
             assert frame.opcode is OP_TEXT or frame.opcode is OP_BINARY
             if decode is None:
@@ -156,7 +154,7 @@ async def get(self, decode: bool | None = None) -> Data:
             # Following frames, for fragmented messages
             while not frame.fin:
                 try:
-                    frame = await self.frames.get()
+                    frame = await self.frames.get(not self.closed)
                 except asyncio.CancelledError:
                     # Put frames already received back into the queue
                     # so that future calls to get() can return them.
@@ -200,12 +198,8 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
                 :meth:`get_iter` concurrently.
 
         """
-        if self.closed:
-            raise EOFError("stream of frames ended")
-
         if self.get_in_progress:
             raise ConcurrencyError("get() or get_iter() is already running")
-
         self.get_in_progress = True
 
         # Locking with get_in_progress prevents concurrent execution
@@ -216,7 +210,7 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
 
         # First frame
         try:
-            frame = await self.frames.get()
+            frame = await self.frames.get(not self.closed)
         except asyncio.CancelledError:
             self.get_in_progress = False
             raise
@@ -236,7 +230,7 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
             # previous fragments — we're streaming them. Canceling get_iter()
             # here will leave the assembler in a stuck state. Future calls to
             # get() or get_iter() will raise ConcurrencyError.
-            frame = await self.frames.get()
+            frame = await self.frames.get(not self.closed)
             self.maybe_resume()
             assert frame.opcode is OP_CONT
             if decode:

src/websockets/sync/messages.py

@@ -69,10 +69,16 @@ def __init__(
     def get_next_frame(self, timeout: float | None = None) -> Frame:
         # Helper to factor out the logic for getting the next frame from the
         # queue, while handling timeouts and reaching the end of the stream.
-        try:
-            frame = self.frames.get(timeout=timeout)
-        except queue.Empty:
-            raise TimeoutError(f"timed out in {timeout:.1f}s") from None
+        if self.closed:
+            try:
+                frame = self.frames.get(block=False)
+            except queue.Empty:
+                raise EOFError("stream of frames ended") from None
+        else:
+            try:
+                frame = self.frames.get(block=True, timeout=timeout)
+            except queue.Empty:
+                raise TimeoutError(f"timed out in {timeout:.1f}s") from None
         if frame is None:
             raise EOFError("stream of frames ended")
         return frame
@@ -87,7 +93,7 @@ def reset_queue(self, frames: Iterable[Frame]) -> None:
             queued = []
             try:
                 while True:
-                    queued.append(self.frames.get_nowait())
+                    queued.append(self.frames.get(block=False))
             except queue.Empty:
                 pass
             for frame in frames:
@@ -123,9 +129,6 @@ def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
 
         """
         with self.mutex:
-            if self.closed:
-                raise EOFError("stream of frames ended")
-
             if self.get_in_progress:
                 raise ConcurrencyError("get() or get_iter() is already running")
             self.get_in_progress = True
@@ -194,9 +197,6 @@ def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
 
         """
         with self.mutex:
-            if self.closed:
-                raise EOFError("stream of frames ended")
-
             if self.get_in_progress:
                 raise ConcurrencyError("get() or get_iter() is already running")
             self.get_in_progress = True
@@ -288,5 +288,6 @@ def close(self) -> None:
 
             self.closed = True
 
-            # Unblock get() or get_iter().
-            self.frames.put(None)
+            if self.get_in_progress:
+                # Unblock get() or get_iter().
+                self.frames.put(None)

tests/asyncio/test_connection.py

@@ -793,14 +793,12 @@ async def test_close_timeout_waiting_for_connection_closed(self):
         # Remove socket.timeout when dropping Python < 3.10.
         self.assertIsInstance(exc.__cause__, (socket.timeout, TimeoutError))
 
-    async def test_close_does_not_wait_for_recv(self):
-        # Closing the connection discards messages buffered in the assembler.
-        # This is allowed by the RFC:
-        # > However, there is no guarantee that the endpoint that has already
-        # > sent a Close frame will continue to process data.
+    async def test_close_preserves_queued_messages(self):
+        """close preserves messages buffered in the assembler."""
         await self.remote_connection.send("😀")
         await self.connection.close()
 
+        self.assertEqual(await self.connection.recv(), "😀")
         with self.assertRaises(ConnectionClosedOK) as raised:
             await self.connection.recv()
 

tests/asyncio/test_messages.py

@@ -395,6 +395,58 @@ async def test_get_iter_fails_after_close(self):
             async for _ in self.assembler.get_iter():
                 self.fail("no fragment expected")
 
+    async def test_get_queued_message_after_close(self):
+        """get returns a message after close is called."""
+        self.assembler.put(Frame(OP_TEXT, b"caf\xc3\xa9"))
+        self.assembler.close()
+        message = await self.assembler.get()
+        self.assertEqual(message, "café")
+
+    async def test_get_iter_queued_message_after_close(self):
+        """get_iter yields a message after close is called."""
+        self.assembler.put(Frame(OP_TEXT, b"caf\xc3\xa9"))
+        self.assembler.close()
+        fragments = await alist(self.assembler.get_iter())
+        self.assertEqual(fragments, ["café"])
+
+    async def test_get_queued_fragmented_message_after_close(self):
+        """get reassembles a fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"a"))
+        self.assembler.close()
+        self.assembler.close()
+        message = await self.assembler.get()
+        self.assertEqual(message, b"tea")
+
+    async def test_get_iter_queued_fragmented_message_after_close(self):
+        """get_iter yields a fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"a"))
+        self.assembler.close()
+        fragments = await alist(self.assembler.get_iter())
+        self.assertEqual(fragments, [b"t", b"e", b"a"])
+
+    async def test_get_partially_queued_fragmented_message_after_close(self):
+        """get raises EOF on a partial fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.close()
+        with self.assertRaises(EOFError):
+            await self.assembler.get()
+
+    async def test_get_iter_partially_queued_fragmented_message_after_close(self):
+        """get_iter yields a partial fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.close()
+        fragments = []
+        with self.assertRaises(EOFError):
+            async for fragment in self.assembler.get_iter():
+                fragments.append(fragment)
+        self.assertEqual(fragments, [b"t", b"e"])
+
     async def test_put_fails_after_close(self):
         """put raises EOFError after close is called."""
         self.assembler.close()

tests/sync/test_connection.py

@@ -543,17 +543,12 @@ def test_close_timeout_waiting_for_connection_closed(self):
         # Remove socket.timeout when dropping Python < 3.10.
         self.assertIsInstance(exc.__cause__, (socket.timeout, TimeoutError))
 
-    def test_close_does_not_wait_for_recv(self):
-        # Closing the connection discards messages buffered in the assembler.
-        # This is allowed by the RFC:
-        # > However, there is no guarantee that the endpoint that has already
-        # > sent a Close frame will continue to process data.
+    def test_close_preserves_queued_messages(self):
+        """close preserves messages buffered in the assembler."""
         self.remote_connection.send("😀")
         self.connection.close()
 
-        close_thread = threading.Thread(target=self.connection.close)
-        close_thread.start()
-
+        self.assertEqual(self.connection.recv(), "😀")
         with self.assertRaises(ConnectionClosedOK) as raised:
             self.connection.recv()
 
@@ -576,10 +571,10 @@ def test_close_idempotency(self):
     def test_close_idempotency_race_condition(self):
         """close waits if the connection is already closing."""
 
-        self.connection.close_timeout = 5 * MS
+        self.connection.close_timeout = 6 * MS
 
         def closer():
-            with self.delay_frames_rcvd(3 * MS):
+            with self.delay_frames_rcvd(4 * MS):
                 self.connection.close()
 
         close_thread = threading.Thread(target=closer)
@@ -591,14 +586,14 @@ def closer():
 
         # Connection isn't closed yet.
         with self.assertRaises(TimeoutError):
-            self.connection.recv(timeout=0)
+            self.connection.recv(timeout=MS)
 
         self.connection.close()
         self.assertNoFrameSent()
 
         # Connection is closed now.
         with self.assertRaises(ConnectionClosedOK):
-            self.connection.recv(timeout=0)
+            self.connection.recv(timeout=MS)
 
         close_thread.join()
 

tests/sync/test_messages.py

@@ -374,6 +374,58 @@ def test_get_iter_fails_after_close(self):
             for _ in self.assembler.get_iter():
                 self.fail("no fragment expected")
 
+    def test_get_queued_message_after_close(self):
+        """get returns a message after close is called."""
+        self.assembler.put(Frame(OP_TEXT, b"caf\xc3\xa9"))
+        self.assembler.close()
+        message = self.assembler.get()
+        self.assertEqual(message, "café")
+
+    def test_get_iter_queued_message_after_close(self):
+        """get_iter yields a message after close is called."""
+        self.assembler.put(Frame(OP_TEXT, b"caf\xc3\xa9"))
+        self.assembler.close()
+        fragments = list(self.assembler.get_iter())
+        self.assertEqual(fragments, ["café"])
+
+    def test_get_queued_fragmented_message_after_close(self):
+        """get reassembles a fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"a"))
+        self.assembler.close()
+        self.assembler.close()
+        message = self.assembler.get()
+        self.assertEqual(message, b"tea")
+
+    def test_get_iter_queued_fragmented_message_after_close(self):
+        """get_iter yields a fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"a"))
+        self.assembler.close()
+        fragments = list(self.assembler.get_iter())
+        self.assertEqual(fragments, [b"t", b"e", b"a"])
+
+    def test_get_partially_queued_fragmented_message_after_close(self):
+        """get raises EOF on a partial fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.close()
+        with self.assertRaises(EOFError):
+            self.assembler.get()
+
+    def test_get_iter_partially_queued_fragmented_message_after_close(self):
+        """get_iter yields a partial fragmented message after close is called."""
+        self.assembler.put(Frame(OP_BINARY, b"t", fin=False))
+        self.assembler.put(Frame(OP_CONT, b"e", fin=False))
+        self.assembler.close()
+        fragments = []
+        with self.assertRaises(EOFError):
+            for fragment in self.assembler.get_iter():
+                fragments.append(fragment)
+        self.assertEqual(fragments, [b"t", b"e"])
+
     def test_put_fails_after_close(self):
         """put raises EOFError after close is called."""
         self.assembler.close()