fix datetime validator

CHANGES.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+* BaseSearchGetRequest datetime validator str_to_interval not allowing GET /search requests with datetime = None ([#662](https://github.com/stac-utils/stac-fastapi/pull/662))
+
 ## [2.5.1] - 2024-04-18
 
 ### Fixed

stac_fastapi/types/stac_fastapi/types/rfc3339.py

@@ -45,9 +45,7 @@ def rfc3339_str_to_datetime(s: str) -> datetime:
     return iso8601.parse_date(s)
 
 
-def str_to_interval(
-    interval: str,
-) -> Optional[DateTimeType]:
+def str_to_interval(interval: Optional[str]) -> Optional[DateTimeType]:
     """Extract a tuple of datetimes from an interval string.
 
     Interval strings are defined by
@@ -56,12 +54,19 @@ def str_to_interval(
     or end (but not both) to be open-ended with '..' or ''.
 
     Args:
-        interval (str) : The interval string to convert to a :class:`datetime.datetime`
-        tuple.
+        interval (str or None): The interval string to convert to a tuple of
+        datetime.datetime objects, or None if no datetime is specified.
+
+    Returns:
+        Optional[DateTimeType]: A tuple of datetime.datetime objects or None if
+        input is None.
 
     Raises:
-        ValueError: If the string is not a valid interval string.
+        ValueError: If the string is not a valid interval string and not None.
     """
+    if interval is None:
+        return None
+
     if not interval:
         raise ValueError("Empty interval string is invalid.")
 

stac_fastapi/types/tests/test_rfc3339.py

@@ -103,3 +103,10 @@ def test_now_functions() -> None:
     assert now1.tzinfo == timezone.utc
 
     rfc3339_str_to_datetime(now_to_rfc3339_str())
+
+
+def test_str_to_interval_with_none():
+    """Test that str_to_interval returns None when provided with None."""
+    assert (
+        str_to_interval(None) is None
+    ), "str_to_interval should return None when input is None"