support passing optional date through CLI (#3273)

* support passing optional date through CLI

Signed-off-by: Blake <[email protected]>

* feedback from review

Signed-off-by: Blake <[email protected]>

* feedback from review

Signed-off-by: Blake <[email protected]>

---------

Signed-off-by: Blake <[email protected]>

Author: blaketastic2

flytekit/interaction/click_types.py

@@ -8,6 +8,7 @@
 import os
 import pathlib
 import sys
+import types
 import typing
 import typing as t
 from typing import cast, get_args
@@ -561,7 +562,14 @@ def convert(
             return value
         try:
             # If the expected Python type is datetime.date, adjust the value to date
-            if self._python_type is datetime.date:
+            is_union = typing.get_origin(self._python_type) in (
+                typing.Union,
+                types.UnionType,
+            )
+            args = typing.get_args(self._python_type)
+            is_date_type = (is_union and datetime.date in args) or self._python_type is datetime.date
+
+            if is_date_type and isinstance(value, datetime.datetime):
                 # Click produces datetime, so converting to date to avoid type mismatch error
                 value = value.date()
             # If the input matches the default value in the launch plan, serialization can be skipped.