fix: to_camel_case fails on leading or trailing underscores (#979)

Changed a prop to `if_` and noticed the `to_camel_case` method throws
with index out of bounds because it ends up trying to access characters
of an empty string. Figured we should preserve leading and trailing
underscores, but convert anything in the middle to camelCase.

plugins/ui/src/deephaven/ui/_internal/utils.py

@@ -71,15 +71,21 @@ def get_component_qualname(component: Any) -> str:
 def to_camel_case(snake_case_text: str) -> str:
     """
     Convert a snake_case string to camelCase.
+    Preserves any leading or trailing underscores.
 
     Args:
         snake_case_text: The snake_case string to convert.
 
     Returns:
         The camelCase string.
     """
-    components = snake_case_text.split("_")
-    return components[0] + "".join((x[0].upper() + x[1:]) for x in components[1:])
+    leading_underscores = len(snake_case_text) - len(snake_case_text.lstrip("_"))
+    trailing_underscores = len(snake_case_text) - len(snake_case_text.rstrip("_"))
+    components = snake_case_text.strip("_").split("_")
+    camel_case_text = components[0] + "".join(
+        (x[0].upper() + x[1:]) for x in components[1:]
+    )
+    return "_" * leading_underscores + camel_case_text + "_" * trailing_underscores
 
 
 def to_react_prop_case(snake_case_text: str) -> str:

plugins/ui/test/deephaven/ui/test_utils.py

@@ -78,6 +78,13 @@ def test_dict_to_camel_case(self):
             dict_to_camel_case({"bar": "biz", "UNSAFE_class_name": "harry"}),
             {"bar": "biz", "UNSAFEClassName": "harry"},
         )
+        # Test leading/trailing underscore
+        self.assertDictEqual(
+            dict_to_camel_case(
+                {"foo_": "bar", "_baz": "biz", "__youre_a_wizard__": "Harry"}
+            ),
+            {"foo_": "bar", "_baz": "biz", "__youreAWizard__": "Harry"},
+        )
 
     def test_dict_to_react_props(self):
         from deephaven.ui._internal.utils import dict_to_react_props
@@ -100,6 +107,13 @@ def test_dict_to_react_props(self):
             ),
             {"bar": "biz", "UNSAFE_className": "harry", "aria-label": "ron"},
         )
+        # Test trailing underscore
+        self.assertDictEqual(
+            dict_to_react_props(
+                {"foo_": "bar", "_baz": "biz", "__youre_a_wizard__": "Harry"}
+            ),
+            {"foo_": "bar", "_baz": "biz", "__youreAWizard__": "Harry"},
+        )
 
     def test_remove_empty_keys(self):
         from deephaven.ui._internal.utils import remove_empty_keys