🐛(back) manage can-edit endpoint without created room in the ws (#1152)

In a scenario where the first user is editing a docs without websocket
and nobody has reached the websocket server first, the y-provider
service will return a 404 and we don't handle this case in the can-edit
endpoint leading to a server error.

src/backend/core/services/collaboration_services.py

@@ -62,10 +62,14 @@ class CollaborationService:
         except requests.RequestException as e:
             raise requests.HTTPError("Failed to get document connection info.") from e
 
-        if response.status_code != 200:
-            raise requests.HTTPError(
-                f"Failed to get document connection info. Status code: {response.status_code}, "
-                f"Response: {response.text}"
-            )
-        result = response.json()
-        return result.get("count", 0), result.get("exists", False)
+        if response.status_code == 200:
+            result = response.json()
+            return result.get("count", 0), result.get("exists", False)
+
+        if response.status_code == 404:
+            return 0, False
+
+        raise requests.HTTPError(
+            f"Failed to get document connection info. Status code: {response.status_code}, "
+            f"Response: {response.text}"
+        )

src/backend/core/tests/documents/test_api_documents_can_edit.py

@@ -246,3 +246,73 @@ def test_api_documents_can_edit_websocket_server_unreachable_fallback_to_no_webs
 
     assert cache.get(f"docs:no-websocket:{document.id}") == "other_session_key"
     assert ws_resp.call_count == 1
+
+
+@responses.activate
+def test_api_documents_can_edit_websocket_server_room_not_found(
+    settings,
+):
+    """
+    When the websocket server returns a 404, the document can be updated like if the user was
+    not connected to the websocket.
+    """
+    user = factories.UserFactory(with_owned_document=True)
+    client = APIClient()
+    client.force_login(user)
+    session_key = client.session.session_key
+
+    document = factories.DocumentFactory(users=[(user, "editor")])
+
+    settings.COLLABORATION_API_URL = "http://example.com/"
+    settings.COLLABORATION_SERVER_SECRET = "secret-token"
+    settings.COLLABORATION_WS_NOT_CONNECTED_READY_ONLY = True
+    endpoint_url = (
+        f"{settings.COLLABORATION_API_URL}get-connections/"
+        f"?room={document.id}&sessionKey={session_key}"
+    )
+    ws_resp = responses.get(endpoint_url, status=404)
+
+    assert cache.get(f"docs:no-websocket:{document.id}") is None
+
+    response = client.get(
+        f"/api/v1.0/documents/{document.id!s}/can-edit/",
+    )
+    assert response.status_code == 200
+    assert response.json() == {"can_edit": True}
+
+    assert ws_resp.call_count == 1
+
+
+@responses.activate
+def test_api_documents_can_edit_websocket_server_room_not_found_other_already_editing(
+    settings,
+):
+    """
+    When the websocket server returns a 404 and another user is editing the document,
+    the response should be can-edit=False.
+    """
+    user = factories.UserFactory(with_owned_document=True)
+    client = APIClient()
+    client.force_login(user)
+    session_key = client.session.session_key
+
+    document = factories.DocumentFactory(users=[(user, "editor")])
+
+    settings.COLLABORATION_API_URL = "http://example.com/"
+    settings.COLLABORATION_SERVER_SECRET = "secret-token"
+    settings.COLLABORATION_WS_NOT_CONNECTED_READY_ONLY = True
+    endpoint_url = (
+        f"{settings.COLLABORATION_API_URL}get-connections/"
+        f"?room={document.id}&sessionKey={session_key}"
+    )
+    ws_resp = responses.get(endpoint_url, status=404)
+
+    cache.set(f"docs:no-websocket:{document.id}", "other_session_key")
+
+    response = client.get(
+        f"/api/v1.0/documents/{document.id!s}/can-edit/",
+    )
+    assert response.status_code == 200
+    assert response.json() == {"can_edit": False}
+
+    assert ws_resp.call_count == 1

src/backend/core/tests/documents/test_api_documents_update.py

@@ -539,6 +539,47 @@ def test_api_documents_update_websocket_server_unreachable_fallback_to_no_websoc
     assert ws_resp.call_count == 1
 
 
+@responses.activate
+def test_api_documents_update_websocket_server_room_not_found_fallback_to_no_websocket_other_users(
+    settings,
+):
+    """
+    When the WebSocket server does not have the room created, the logic should fallback to
+    no-WebSocket. If another user is already editing, the update must be denied.
+    """
+    user = factories.UserFactory(with_owned_document=True)
+    client = APIClient()
+    client.force_login(user)
+    session_key = client.session.session_key
+
+    document = factories.DocumentFactory(users=[(user, "editor")])
+
+    new_document_values = serializers.DocumentSerializer(
+        instance=factories.DocumentFactory()
+    ).data
+    new_document_values["websocket"] = False
+    settings.COLLABORATION_API_URL = "http://example.com/"
+    settings.COLLABORATION_SERVER_SECRET = "secret-token"
+    settings.COLLABORATION_WS_NOT_CONNECTED_READY_ONLY = True
+    endpoint_url = (
+        f"{settings.COLLABORATION_API_URL}get-connections/"
+        f"?room={document.id}&sessionKey={session_key}"
+    )
+    ws_resp = responses.get(endpoint_url, status=404)
+
+    cache.set(f"docs:no-websocket:{document.id}", "other_session_key")
+
+    response = client.put(
+        f"/api/v1.0/documents/{document.id!s}/",
+        new_document_values,
+        format="json",
+    )
+    assert response.status_code == 403
+
+    assert cache.get(f"docs:no-websocket:{document.id}") == "other_session_key"
+    assert ws_resp.call_count == 1
+
+
 @responses.activate
 def test_api_documents_update_force_websocket_param_to_true(settings):
     """