feat(framework) Introduce flwr-serverapp CLI entrypoint (#4350)

pyproject.toml

@@ -56,7 +56,8 @@ flower-simulation = "flwr.simulation.run_simulation:run_simulation_from_cli"
 # Deployment Engine
 flower-superlink = "flwr.server.app:run_superlink"
 flower-supernode = "flwr.client.supernode.app:run_supernode"
-flower-server-app = "flwr.server.run_serverapp:run_server_app"
+flwr-serverapp = "flwr.server.serverapp:flwr_serverapp"
+flower-server-app = "flwr.server.run_serverapp:run_server_app" # Deprecated
 flwr-clientapp = "flwr.client.clientapp:flwr_clientapp"
 flower-client-app = "flwr.client.supernode:run_client_app" # Deprecated
 

src/py/flwr/server/serverapp/__init__.py

@@ -0,0 +1,22 @@
+# Copyright 2024 Flower Labs GmbH. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Flower AppIO service."""
+
+
+from .app import flwr_serverapp as flwr_serverapp
+
+__all__ = [
+    "flwr_serverapp",
+]

src/py/flwr/server/serverapp/app.py

@@ -0,0 +1,20 @@
+# Copyright 2024 Flower Labs GmbH. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Flower ServerApp process."""
+
+
+def flwr_serverapp() -> None:
+    """Run process-isolated Flower ServerApp."""
+    raise NotImplementedError()