Added try except statement around isinstance check to avoid excepti…

…on (#627)

* Added try except statement around `isinstance` check to avoid exception.

tests/test_callback_typecheck.py

@@ -131,3 +131,12 @@ def expect_union(arg: Union[str, int]) -> Union[str, int]:
     assert isinstance(callback_typecheck(expect_union)(1.5), str)
 
     ############################################################
+
+    def expect_union_list(arg: Union[List[str], str]) -> Union[List[str], str]:
+        return arg
+
+    assert isinstance(callback_typecheck(expect_union_list)(["1", "2"]), list)
+    assert isinstance(callback_typecheck(expect_union_list)(["1", "2"])[0], str)
+    assert isinstance(callback_typecheck(expect_union_list)("1"), str)
+
+    ############################################################

webviz_config/utils/_callback_typecheck.py

@@ -10,7 +10,7 @@ class ConversionError(Exception):
 
 
 def convert(arg: Any, convert_to: T) -> T:
-    # pylint: disable=too-many-return-statements, too-many-branches
+    # pylint: disable=too-many-return-statements, too-many-branches, too-many-nested-blocks
     additional_error_message: str = ""
     try:
         if convert_to is None and arg is None:
@@ -57,8 +57,11 @@ def convert(arg: Any, convert_to: T) -> T:
         if get_origin(convert_to) is Union:
             if "__args__" in dir(convert_to):
                 for convert_type in convert_to.__args__:  # type: ignore[attr-defined]
-                    if isinstance(arg, convert_type):
-                        return arg
+                    try:
+                        if isinstance(arg, convert_type):
+                            return arg
+                    except TypeError:
+                        pass
                 for convert_type in convert_to.__args__:  # type: ignore[attr-defined]
                     try:
                         return convert(arg, convert_type)