fix(matrix): send non-empty POST body on room join for Continuwuity compatibility (#5248)

nanobot/channels/matrix/runtime.py

@@ -24,10 +24,12 @@ try:
     import nh3
     from mistune import HTMLRenderer, create_markdown
     from nio import (
+        Api,
         AsyncClient,
         AsyncClientConfig,
         InviteEvent,
         JoinError,
+        JoinResponse,
         KeyVerificationCancel,
         KeyVerificationEvent,
         KeyVerificationKey,
@@ -43,6 +45,7 @@ try:
         RoomSendResponse,
         RoomTypingError,
         SyncError,
+        SyncResponse,
         ToDeviceError,
         UploadError,
     )
@@ -701,6 +704,7 @@ class MatrixChannel(BaseChannel):
         client.add_response_callback(self._on_sync_error, SyncError)
         client.add_response_callback(self._on_join_error, JoinError)
         client.add_response_callback(self._on_send_error, RoomSendError)
+        client.add_response_callback(self._on_sync_invite_fallback, SyncResponse)
 
     def _is_sas_sender_allowed(self, sender: str) -> bool:
         return bool(sender and self.is_allowed(sender))
@@ -782,6 +786,49 @@ class MatrixChannel(BaseChannel):
                 with suppress(Exception):
                     self.client.stop_sync_forever()
 
+    async def _join_room_safe(self, room_id: str) -> bool:
+        """Join a room, sending a non-empty POST body.
+
+        nio's ``Api.join()`` produces a POST with no body. Some homeservers
+        (notably Continuwuity) reject empty bodies with ``M_BAD_JSON``.
+        Sending ``"{}"`` satisfies both strict and lenient servers.
+        """
+        client = self._require_client()
+        method, path = Api.join(client.access_token, room_id)
+        try:
+            resp = cast(
+                JoinResponse | JoinError,
+                await client._send(  # type: ignore[reportPrivateUsage, reportUnknownMemberType]
+                    JoinResponse, method, path, data="{}"
+                ),
+            )
+        except Exception:
+            self.logger.error("Matrix join request exception for room={}", room_id, exc_info=True)
+            return False
+        if isinstance(resp, JoinError):
+            self.logger.error("Matrix auto-join failed for room={}: {}", room_id, resp)
+            return False
+        self.logger.info("Matrix auto-join succeeded: {}", room_id)
+        return True
+
+    async def _on_sync_invite_fallback(self, response: SyncResponse) -> None:
+        """Safety net: join pending invites that the event callback may have missed.
+
+        Some homeservers (e.g. Continuwuity) deliver each invite only once.
+        If ``_on_room_invite`` fires but the join fails, the sync token
+        advances and the invite is never re-delivered. This callback inspects
+        the same ``SyncResponse`` for pending invites and joins them, acting
+        as a fallback alongside the event-based callback.
+        """
+        if not response.rooms or not response.rooms.invite:
+            return
+        for room_id, invite_info in response.rooms.invite.items():
+            for event in cast(list[Any], invite_info.invite_state):
+                sender = getattr(event, "sender", None)
+                if sender and self.is_allowed(cast(str, sender)):
+                    await self._join_room_safe(room_id)
+                    break
+
     async def _on_join_error(self, response: JoinError) -> None:
         self._log_response_error("join", response)
 
@@ -838,8 +885,7 @@ class MatrixChannel(BaseChannel):
 
     async def _on_room_invite(self, room: MatrixRoom, event: InviteEvent) -> None:
         if self.is_allowed(event.sender):
-            client = self._require_client()
-            await client.join(room.room_id)
+            await self._join_room_safe(room.room_id)
 
     def _is_direct_room(self, room: MatrixRoom) -> bool:
         count = getattr(room, "member_count", None)

nanobot/channels/matrix/tests/test_matrix_channel.py

@@ -4,13 +4,14 @@ import asyncio
 import sys
 from pathlib import Path
 from types import SimpleNamespace
+from urllib.parse import unquote
 
 import pytest
 
 pytest.importorskip("nio")
 pytest.importorskip("nh3")
 pytest.importorskip("mistune")
-from nio import RoomSendResponse, SyncError
+from nio import JoinResponse, RoomSendResponse, SyncError
 
 import nanobot.channels.matrix.runtime as matrix_module
 from nanobot.bus.events import OutboundMessage
@@ -104,6 +105,15 @@ class _FakeAsyncClient:
     async def join(self, room_id: str) -> None:
         self.join_calls.append(room_id)
 
+    async def _send(self, response_class, method, path, data=None, **kwargs):
+        """Minimal mock for nio's ``_send`` used by ``_join_room_safe``."""
+        if response_class is JoinResponse and method == "POST" and "/join/" in path:
+            encoded = path.split("/join/")[1].split("?")[0]
+            room_id = unquote(encoded)
+            self.join_calls.append(room_id)
+            return JoinResponse(room_id=room_id)
+        return response_class()
+
     async def accept_key_verification(self, transaction_id: str):
         self.operation_calls.append(f"accept:{transaction_id}")
         self.accept_key_verification_calls.append(transaction_id)
@@ -308,7 +318,7 @@ async def test_start_skips_load_store_when_device_id_missing(
     assert clients[0].load_store_called is False
     assert len(clients[0].callbacks) == 3
     assert clients[0].to_device_callbacks == []
-    assert len(clients[0].response_callbacks) == 3
+    assert len(clients[0].response_callbacks) == 4
 
     await channel.stop()
 
@@ -590,6 +600,7 @@ async def test_room_invite_joins_when_sender_allowed() -> None:
 
     assert client.join_calls == ["!room:matrix.org"]
 
+
 @pytest.mark.asyncio
 async def test_room_invite_respects_allow_list_when_configured() -> None:
     channel = MatrixChannel(_make_config(allow_from=["@bob:matrix.org"]), MessageBus())
@@ -604,6 +615,61 @@ async def test_room_invite_respects_allow_list_when_configured() -> None:
     assert client.join_calls == []
 
 
+@pytest.mark.asyncio
+async def test_on_sync_invite_fallback_joins_pending_invites() -> None:
+    """_on_sync_invite_fallback joins rooms from sync invite_state for allowed senders."""
+    channel = MatrixChannel(
+        _make_config(allow_from=["@alice:matrix.org"]), MessageBus()
+    )
+    client = _FakeAsyncClient("", "", "", None)
+    channel.client = client
+
+    invite_event = SimpleNamespace(sender="@alice:matrix.org")
+    invite_info = SimpleNamespace(invite_state=[invite_event])
+    rooms = SimpleNamespace(invite={"!room:matrix.org": invite_info})
+    response = SimpleNamespace(rooms=rooms)
+
+    await channel._on_sync_invite_fallback(response)
+
+    assert client.join_calls == ["!room:matrix.org"]
+
+
+@pytest.mark.asyncio
+async def test_on_sync_invite_fallback_skips_when_no_invites() -> None:
+    """_on_sync_invite_fallback is a no-op when sync has no invites."""
+    channel = MatrixChannel(
+        _make_config(allow_from=["@alice:matrix.org"]), MessageBus()
+    )
+    client = _FakeAsyncClient("", "", "", None)
+    channel.client = client
+
+    rooms = SimpleNamespace(invite={})
+    response = SimpleNamespace(rooms=rooms)
+
+    await channel._on_sync_invite_fallback(response)
+
+    assert client.join_calls == []
+
+
+@pytest.mark.asyncio
+async def test_on_sync_invite_fallback_skips_denied_sender() -> None:
+    """_on_sync_invite_fallback respects the allow list."""
+    channel = MatrixChannel(
+        _make_config(allow_from=["@bob:matrix.org"]), MessageBus()
+    )
+    client = _FakeAsyncClient("", "", "", None)
+    channel.client = client
+
+    invite_event = SimpleNamespace(sender="@alice:matrix.org")
+    invite_info = SimpleNamespace(invite_state=[invite_event])
+    rooms = SimpleNamespace(invite={"!room:matrix.org": invite_info})
+    response = SimpleNamespace(rooms=rooms)
+
+    await channel._on_sync_invite_fallback(response)
+
+    assert client.join_calls == []
+
+
 @pytest.mark.asyncio
 async def test_on_message_sets_typing_for_allowed_sender() -> None:
     channel = MatrixChannel(_make_config(), MessageBus())