feat: implement set_value_if_changed method to optimize value updates and add tests

Author: Mike Prosser

src/nipanel/_streamlit_panel_initializer.py

@@ -84,4 +84,4 @@ def _sync_session_state(panel: StreamlitPanelValueAccessor) -> None:
     for key in st.session_state.keys():
         value = st.session_state[key]
         if is_supported_type(value):
-            panel.set_value(str(key), value)
+            panel.set_value_if_changed(str(key), value)

src/nipanel/_streamlit_panel_value_accessor.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import collections
 from typing import final
 
 import grpc
@@ -17,6 +18,8 @@ class StreamlitPanelValueAccessor(PanelValueAccessor):
     This class should only be used within a Streamlit script.
     """
 
+    __slots__ = ["_last_values"]
+
     def __init__(
         self,
         panel_id: str,
@@ -43,3 +46,19 @@ def __init__(
             grpc_channel_pool=grpc_channel_pool,
             grpc_channel=grpc_channel,
         )
+        self._last_values: collections.defaultdict[str, object] = collections.defaultdict(
+            lambda: object()
+        )
+
+    def set_value_if_changed(self, value_id: str, value: object) -> None:
+        """Set the value for a control on the panel only if it has changed since the last call.
+
+        This method helps reduce unnecessary updates when the value hasn't changed.
+
+        Args:
+            value_id: The id of the value
+            value: The value to set
+        """
+        if value != self._last_values[value_id]:
+            self.set_value(value_id, value)
+            self._last_values[value_id] = value

src/nipanel/controls/_enum_selectbox.py

@@ -5,13 +5,13 @@
 
 import streamlit as st
 
-from nipanel._panel_value_accessor import PanelValueAccessor
+from nipanel._streamlit_panel_value_accessor import StreamlitPanelValueAccessor
 
 T = TypeVar("T", bound=Enum)
 
 
 def enum_selectbox(
-    panel: PanelValueAccessor,
+    panel: StreamlitPanelValueAccessor,
     label: str,
     value: T,
     key: str,
@@ -49,5 +49,5 @@ def enum_selectbox(
         label, options=options, format_func=format_func, index=default_index, disabled=disabled
     )
     enum_value = enum_class[box_tuple[0]]
-    panel.set_value(key, enum_value)
+    panel.set_value_if_changed(key, enum_value)
     return enum_value

src/nipanel/controls/_flag_checkboxes.py

@@ -5,13 +5,13 @@
 
 import streamlit as st
 
-from nipanel._panel_value_accessor import PanelValueAccessor
+from nipanel._streamlit_panel_value_accessor import StreamlitPanelValueAccessor
 
 T = TypeVar("T", bound=Flag)
 
 
 def flag_checkboxes(
-    panel: PanelValueAccessor,
+    panel: StreamlitPanelValueAccessor,
     label: str,
     value: T,
     key: str,
@@ -69,5 +69,5 @@ def flag_checkboxes(
             selected_flags &= ~flag
 
     # Store the selected flags in the panel
-    panel.set_value(key, selected_flags)
+    panel.set_value_if_changed(key, selected_flags)
     return selected_flags

tests/unit/test_streamlit_panel.py

@@ -297,7 +297,7 @@ def test___enum_type___set_value___gets_same_value(
     fake_panel_channel: grpc.Channel,
     value_payload: enum.Enum,
 ) -> None:
-    """Test that set_value() and get_value() work for builtin scalar types."""
+    """Test that set_value() and get_value() work for enum types."""
     panel = StreamlitPanel("my_panel", "path/to/script", grpc_channel=fake_panel_channel)
 
     value_id = "test_id"

tests/unit/test_streamlit_panel_value_accessor.py

@@ -0,0 +1,111 @@
+import grpc
+
+from nipanel import StreamlitPanelValueAccessor
+from tests.types import MyIntEnum
+from tests.utils._fake_python_panel_service import FakePythonPanelService
+
+
+def test___no_previous_value___set_value_if_changed___sets_value(
+    fake_panel_channel: grpc.Channel,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+
+    accessor.set_value_if_changed("test_id", "test_value")
+
+    assert accessor.get_value("test_id") == "test_value"
+
+
+def test___set_value_if_changed___set_same_value___does_not_set_value_again(
+    fake_panel_channel: grpc.Channel,
+    fake_python_panel_service: FakePythonPanelService,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", "test_value")
+    initial_set_count = fake_python_panel_service.servicer.set_count
+
+    accessor.set_value_if_changed("test_id", "test_value")
+
+    assert fake_python_panel_service.servicer.set_count == initial_set_count
+    assert accessor.get_value("test_id") == "test_value"
+
+
+def test___set_value_if_changed___set_different_value___sets_new_value(
+    fake_panel_channel: grpc.Channel,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", "test_value")
+
+    accessor.set_value_if_changed("test_id", "new_value")
+
+    assert accessor.get_value("test_id") == "new_value"
+
+
+def test___set_value_if_changed___different_value_ids___tracks_separately(
+    fake_panel_channel: grpc.Channel,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+
+    accessor.set_value_if_changed("id1", "value1")
+    accessor.set_value_if_changed("id2", "value2")
+
+    accessor.set_value_if_changed("id1", "value1")
+    accessor.set_value_if_changed("id2", "new_value2")
+
+    assert accessor.get_value("id1") == "value1"
+    assert accessor.get_value("id2") == "new_value2"
+
+
+def test___set_value_if_changed_with_list_value___set_same_value___does_not_set_value_again(
+    fake_panel_channel: grpc.Channel,
+    fake_python_panel_service: FakePythonPanelService,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", [1, 2, 3])
+    initial_set_count = fake_python_panel_service.servicer.set_count
+
+    accessor.set_value_if_changed("test_id", [1, 2, 3])
+
+    assert fake_python_panel_service.servicer.set_count == initial_set_count
+    assert accessor.get_value("test_id") == [1, 2, 3]
+
+
+def test___set_value_if_changed_with_list_value___set_different_value___sets_new_value(
+    fake_panel_channel: grpc.Channel,
+    fake_python_panel_service: FakePythonPanelService,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", [1, 2, 3])
+    initial_set_count = fake_python_panel_service.servicer.set_count
+
+    accessor.set_value_if_changed("test_id", [1, 2, 4])
+
+    assert fake_python_panel_service.servicer.set_count > initial_set_count
+    assert accessor.get_value("test_id") == [1, 2, 4]
+
+
+def test___set_value_if_changed_with_enum_value___set_same_value___does_not_set_value_again(
+    fake_panel_channel: grpc.Channel,
+    fake_python_panel_service: FakePythonPanelService,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", MyIntEnum.VALUE20)
+    initial_set_count = fake_python_panel_service.servicer.set_count
+
+    accessor.set_value_if_changed("test_id", MyIntEnum.VALUE20)
+
+    assert fake_python_panel_service.servicer.set_count == initial_set_count
+    assert accessor.get_value("test_id") == 20  # Enums are stored as their values
+
+
+def test___set_value_if_changed_with_enum_value___set_different_value___sets_new_value(
+    fake_panel_channel: grpc.Channel,
+    fake_python_panel_service: FakePythonPanelService,
+) -> None:
+    accessor = StreamlitPanelValueAccessor("panel_id", grpc_channel=fake_panel_channel)
+    accessor.set_value_if_changed("test_id", MyIntEnum.VALUE20)
+    initial_set_count = fake_python_panel_service.servicer.set_count
+
+    accessor.set_value_if_changed("test_id", MyIntEnum.VALUE30)
+
+    assert fake_python_panel_service.servicer.set_count > initial_set_count
+    assert accessor.get_value("test_id") == 30  # New enum value should be set

tests/utils/_fake_python_panel_servicer.py

@@ -26,6 +26,7 @@ def __init__(self) -> None:
         self._panel_is_running: dict[str, bool] = {}
         self._panel_value_ids: dict[str, dict[str, Any]] = {}
         self._fail_next_start_panel = False
+        self._set_count: int = 0
         self._notification_count: int = 0
         self._python_path: str = ""
 
@@ -70,6 +71,7 @@ def SetValue(self, request: SetValueRequest, context: Any) -> SetValueResponse:
         """Trivial implementation for testing."""
         self._init_panel(request.panel_id)
         self._panel_value_ids[request.panel_id][request.value_id] = request.value
+        self._set_count += 1
         if request.notify:
             self._notification_count += 1
         return SetValueResponse()
@@ -78,6 +80,11 @@ def fail_next_start_panel(self) -> None:
         """Set whether the StartPanel method should fail the next time it is called."""
         self._fail_next_start_panel = True
 
+    @property
+    def set_count(self) -> int:
+        """Get the total number of times SetValue was called."""
+        return self._set_count
+
     @property
     def notification_count(self) -> int:
         """Get the number of notifications sent from SetValue."""