Add a default value parameter to get_value() (#74)

* add default value to get_value()

* revert sample_panel

---------

Co-authored-by: Mike Prosser <Mike.Prosser@emerson.com>

Author: mikeprosserni

examples/sample/sample_panel.py

@@ -18,8 +18,8 @@
     st.write("List")
 
 with col2:
-    st.write(panel.get_value("sample_string"))
-    st.write(panel.get_value("sample_int"))
-    st.write(panel.get_value("sample_float"))
-    st.write(panel.get_value("sample_bool"))
-    st.write(panel.get_value("float_values"))
+    st.write(panel.get_value("sample_string", ""))
+    st.write(panel.get_value("sample_int", 0))
+    st.write(panel.get_value("sample_float", 0.0))
+    st.write(panel.get_value("sample_bool", False))
+    st.write(panel.get_value("float_values", []))

src/nipanel/_panel_value_accessor.py

@@ -41,16 +41,23 @@ def panel_id(self) -> str:
         """Read-only accessor for the panel ID."""
         return self._panel_id
 
-    def get_value(self, value_id: str) -> object:
-        """Get the value for a control on the panel.
+    def get_value(self, value_id: str, default_value: object = None) -> object:
+        """Get the value for a control on the panel with an optional default value.
 
         Args:
             value_id: The id of the value
+            default_value: The default value to return if the value is not set
 
         Returns:
-            The value
+            The value, or the default value if not set
         """
-        return self._panel_client.get_value(self._panel_id, value_id)
+        try:
+            return self._panel_client.get_value(self._panel_id, value_id)
+        except grpc.RpcError as e:
+            if e.code() == grpc.StatusCode.NOT_FOUND and default_value is not None:
+                return default_value
+            else:
+                raise e
 
     def set_value(self, value_id: str, value: object) -> None:
         """Set the value for a control on the panel.

tests/unit/test_streamlit_panel.py

@@ -123,7 +123,7 @@ def test___panel___set_value___sets_value(
     }
 
 
-def test___panel___get_unset_value___raises_exception(
+def test___panel___get_unset_value_with_no_default___raises_exception(
     fake_panel_channel: grpc.Channel,
 ) -> None:
     """Test that get_value() raises an exception for an unset value."""
@@ -146,6 +146,30 @@ def test___panel___set_value___gets_value(
     assert panel.get_value(value_id) == string_value
 
 
+def test___set_value___get_value_ignores_default(
+    fake_panel_channel: grpc.Channel,
+) -> None:
+    panel = StreamlitPanel("my_panel", "path/to/script", grpc_channel=fake_panel_channel)
+
+    value_id = "test_id"
+    string_value = "test_value"
+    panel.set_value(value_id, string_value)
+
+    assert panel.get_value(value_id, "default") == string_value
+
+
+def test___get_value_returns_default_when_value_not_set(
+    fake_panel_channel: grpc.Channel,
+) -> None:
+    panel = StreamlitPanel("my_panel", "path/to/script", grpc_channel=fake_panel_channel)
+
+    assert panel.get_value("missing_string", "default") == "default"
+    assert panel.get_value("missing_int", 123) == 123
+    assert panel.get_value("missing_float", 1.23) == 1.23
+    assert panel.get_value("missing_bool", True) is True
+    assert panel.get_value("missing_list", [1, 2, 3]) == [1, 2, 3]
+
+
 @pytest.mark.parametrize(
     "value_payload",
     [

tests/utils/_fake_python_panel_servicer.py

@@ -59,6 +59,8 @@ def EnumeratePanels(  # noqa: N802
 
     def GetValue(self, request: GetValueRequest, context: Any) -> GetValueResponse:  # noqa: N802
         """Trivial implementation for testing."""
+        if request.value_id not in self._panel_value_ids.get(request.panel_id, {}):
+            context.abort(grpc.StatusCode.NOT_FOUND, "Value ID not found in panel")
         value = self._panel_value_ids[request.panel_id][request.value_id]
         return GetValueResponse(value=value)