Add the ability to hide a DM conversation (#52 follow-up)

Neither participant could get rid of a DM at all -- Leave/Delete were
both deliberately hidden for DMs during the initial build to sidestep
an edge case (removing a membership would break find_or_create_dm's
exactly-two-members assumption), but that left no way out whatsoever.

RoomMembership.hidden_at is a per-viewer display flag, not a
membership deletion: hiding a DM only sets it on your own membership
row, so it disappears from just your sidebar without touching the
other participant's copy or any messages. It's automatically cleared
(reappearing) in two cases: a new message arrives in the room
(broadcast_new_message), or find_or_create_dm resolves back to the
same room because either person re-opens it from the People list --
both count as the conversation being active again.

Also fixes two now-flaky tests (test_message_edit, test_reactions):
broadcast_new_message doing more work before returning shifted timing
enough to expose a pre-existing race where a per-user-channel frame
(desktop_notification/unread_update) could legitimately arrive before
a connection's own "joined" ack. Broadened their existing _recv()
noise-filtering helper (already used for member_updated) to cover
those types too, and used it at the two call sites that were reading
raw receive_json() instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/tests/test_direct_messages.py

@@ -3,10 +3,32 @@ import uuid
 from sqlalchemy import select
 
 from app.models import Room, RoomMembership
+from app.schemas.user import UserCreate
+from app.services.auth_service import register_user
 from app.services.room_service import dm_room_name
 from tests.conftest import login_as, register_and_login
 
 
+def _unique(prefix: str) -> str:
+    return f"{prefix}-{uuid.uuid4().hex[:8]}"
+
+
+def _register_ws(ws_client, username: str) -> dict:
+    async def _seed():
+        async with ws_client.session_factory() as session:
+            await register_user(
+                session,
+                UserCreate(username=username, email=f"{username}@example.com", password="password123"),
+            )
+
+    ws_client.portal.call(_seed)
+    resp = ws_client.post(
+        "/api/auth/login", json={"username_or_email": username, "password": "password123"}
+    )
+    assert resp.status_code == 200, resp.text
+    return resp.json()
+
+
 async def test_start_dm_creates_private_room_with_both_members(client, db_session):
     alice = await register_and_login(client, db_session, username="alice")
     await client.post("/api/auth/logout")
@@ -176,3 +198,80 @@ async def test_dm_rejects_add_member_and_join(client, db_session):
     await login_as(client, "carol")
     resp = await client.post(f"/api/rooms/{dm['id']}/join")
     assert resp.status_code == 400
+
+
+async def test_hide_dm_removes_it_from_mine_for_that_user_only(client, db_session):
+    alice = await register_and_login(client, db_session, username="alice")
+    await client.post("/api/auth/logout")
+    bob = await register_and_login(client, db_session, username="bob")
+    dm = (await client.post("/api/rooms/dm", json={"other_user_id": alice["id"]})).json()
+
+    resp = await client.post(f"/api/rooms/{dm['id']}/hide")
+    assert resp.status_code == 204
+
+    mine = (await client.get("/api/rooms/mine")).json()
+    assert all(r["id"] != dm["id"] for r in mine)
+
+    # Alice never hid it -- still sees it, proving this is per-viewer, not
+    # something that touched the room or bob's membership for everyone.
+    await client.post("/api/auth/logout")
+    await login_as(client, "alice")
+    mine = (await client.get("/api/rooms/mine")).json()
+    assert any(r["id"] == dm["id"] for r in mine)
+
+
+async def test_hide_dm_rejects_regular_rooms(client, db_session):
+    await register_and_login(client, db_session, username="alice")
+    room = (await client.post("/api/rooms", json={"name": "general"})).json()
+    resp = await client.post(f"/api/rooms/{room['id']}/hide")
+    assert resp.status_code == 400
+
+
+async def test_starting_a_dm_again_unhides_it(client, db_session):
+    alice = await register_and_login(client, db_session, username="alice")
+    await client.post("/api/auth/logout")
+    bob = await register_and_login(client, db_session, username="bob")
+    dm = (await client.post("/api/rooms/dm", json={"other_user_id": alice["id"]})).json()
+
+    await client.post(f"/api/rooms/{dm['id']}/hide")
+    mine = (await client.get("/api/rooms/mine")).json()
+    assert all(r["id"] != dm["id"] for r in mine)
+
+    # bob clicking alice in the People list again -- find_or_create_dm
+    # resolves to the same room and un-hides it for him.
+    resp = await client.post("/api/rooms/dm", json={"other_user_id": alice["id"]})
+    assert resp.status_code == 201
+    assert resp.json()["id"] == dm["id"]
+
+    mine = (await client.get("/api/rooms/mine")).json()
+    assert any(r["id"] == dm["id"] for r in mine)
+
+
+def test_new_message_unhides_dm_for_both_participants(ws_client):
+    alice = _register_ws(ws_client, _unique("alice"))
+    bob = _register_ws(ws_client, _unique("bob"))  # ws_client is now logged in as bob
+    dm = ws_client.post("/api/rooms/dm", json={"other_user_id": alice["id"]}).json()
+
+    ws_client.post(f"/api/rooms/{dm['id']}/hide")
+    assert all(r["id"] != dm["id"] for r in ws_client.get("/api/rooms/mine").json())
+
+    ws_client.post(
+        "/api/auth/login", json={"username_or_email": alice["username"], "password": "password123"}
+    )
+    with ws_client.websocket_connect("/ws/chat") as ws:
+        ws.send_json({"type": "join", "room_id": dm["id"]})
+        assert ws.receive_json()["type"] == "joined"
+        ws.send_json({"type": "message", "room_id": dm["id"], "content": "you there?"})
+        ws.receive_json()
+        # Sync barrier (see test_mentions.py's identical helper): the
+        # message ack only proves the room-level broadcast happened, not
+        # that broadcast_new_message's own continuation (which un-hides
+        # the room) has finished -- a second frame's own ack proves that.
+        ws.send_json({"type": "join", "room_id": dm["id"]})
+        assert ws.receive_json()["type"] == "joined"
+
+    # bob never re-opened the DM himself -- alice's message alone unhid it.
+    ws_client.post(
+        "/api/auth/login", json={"username_or_email": bob["username"], "password": "password123"}
+    )
+    assert any(r["id"] == dm["id"] for r in ws_client.get("/api/rooms/mine").json())

backend/tests/test_message_edit.py

@@ -8,13 +8,19 @@ def _unique(prefix: str) -> str:
     return f"{prefix}-{uuid.uuid4().hex[:8]}"
 
 
+_NOISE_TYPES = {"member_updated", "desktop_notification", "unread_update"}
+
+
 def _recv(ws) -> dict:
-    """Reads the next frame, transparently discarding member_updated
-    presence-change broadcasts -- another connection in the same room going
-    online/offline is real, expected noise these tests aren't about."""
+    """Reads the next frame, transparently discarding presence/offline-
+    notify noise -- another connection in the same room going online/
+    offline, or a per-user-channel side effect of an earlier offline
+    member's own message, can legitimately arrive right as a connection is
+    established, before its own "joined" ack. Not what these tests are
+    about."""
     while True:
         msg = ws.receive_json()
-        if msg.get("type") != "member_updated":
+        if msg.get("type") not in _NOISE_TYPES:
             return msg
 
 
@@ -90,7 +96,7 @@ def test_ws_edit_rejects_non_author(ws_client):
         )
         with ws_client.websocket_connect("/ws/chat") as bob_ws:
             bob_ws.send_json({"type": "join", "room_id": room["id"]})
-            assert bob_ws.receive_json()["type"] == "joined"
+            assert _recv(bob_ws)["type"] == "joined"
             bob_ws.send_json(
                 {
                     "type": "edit",
@@ -116,7 +122,7 @@ def test_edit_fans_out_across_instances(ws_client_factory):
 
     with instance2.websocket_connect("/ws/chat") as bob_ws:
         bob_ws.send_json({"type": "join", "room_id": room["id"]})
-        assert bob_ws.receive_json()["type"] == "joined"
+        assert _recv(bob_ws)["type"] == "joined"
 
         with instance1.websocket_connect("/ws/chat") as alice_ws:
             alice_ws.send_json({"type": "join", "room_id": room["id"]})

backend/tests/test_reactions.py

@@ -9,13 +9,19 @@ def _unique(prefix: str) -> str:
     return f"{prefix}-{uuid.uuid4().hex[:8]}"
 
 
+_NOISE_TYPES = {"member_updated", "desktop_notification", "unread_update"}
+
+
 def _recv(ws) -> dict:
-    """Reads the next frame, transparently discarding member_updated
-    presence-change broadcasts -- another connection in the same room going
-    online/offline is real, expected noise these tests aren't about."""
+    """Reads the next frame, transparently discarding presence/offline-
+    notify noise -- another connection in the same room going online/
+    offline, or a per-user-channel side effect of an earlier offline
+    member's own message, can legitimately arrive right as a connection is
+    established, before its own "joined" ack. Not what these tests are
+    about."""
     while True:
         msg = ws.receive_json()
-        if msg.get("type") != "member_updated":
+        if msg.get("type") not in _NOISE_TYPES:
             return msg
 
 
@@ -122,7 +128,7 @@ def test_reaction_broadcasts_to_other_room_members(ws_client):
         )
         with ws_client.websocket_connect("/ws/chat") as bob_ws:
             bob_ws.send_json({"type": "join", "room_id": room["id"]})
-            assert bob_ws.receive_json()["type"] == "joined"
+            assert _recv(bob_ws)["type"] == "joined"
 
             ws_client.post(
                 "/api/auth/login",