fix format_datetime_range

Author: Yuri Zmytrakov

stac_fastapi/core/stac_fastapi/core/datetime_utils.py

@@ -5,34 +5,73 @@
 from stac_fastapi.types.rfc3339 import rfc3339_str_to_datetime
 
 
-def format_datetime_range(date_str: str) -> str:
-    """
-    Convert a datetime range string into a normalized UTC string for API requests using rfc3339_str_to_datetime.
+# def format_datetime_range(date_str: str) -> str:
+#     """
+#     Convert a datetime range string into a normalized UTC string for API requests using rfc3339_str_to_datetime.
+
+#     Args:
+#         date_str (str): A string containing two datetime values separated by a '/'.
+
+#     Returns:
+#         str: A string formatted as 'YYYY-MM-DDTHH:MM:SSZ/YYYY-MM-DDTHH:MM:SSZ', with '..' used if any element is None.
+#     """
+
+#     def normalize(dt):
+#         dt = dt.strip()
+#         if not dt or dt == "..":
+#             return ".."
+#         dt_obj = rfc3339_str_to_datetime(dt)
+#         dt_utc = dt_obj.astimezone(timezone.utc)
+#         return dt_utc.strftime("%Y-%m-%dT%H:%M:%SZ")
+
+#     if not isinstance(date_str, str):
+#         return "../.."
+#     if "/" not in date_str:
+#         return f"{normalize(date_str)}/{normalize(date_str)}"
+#     try:
+#         start, end = date_str.split("/", 1)
+#     except Exception:
+#         return "../.."
+#     return f"{normalize(start)}/{normalize(end)}"
 
-    Args:
-        date_str (str): A string containing two datetime values separated by a '/'.
 
-    Returns:
-        str: A string formatted as 'YYYY-MM-DDTHH:MM:SSZ/YYYY-MM-DDTHH:MM:SSZ', with '..' used if any element is None.
+def format_datetime_range(date_str: str) -> str:
+    """
+    Convert a datetime range string while preserving millisecond precision.
     """
-
-    def normalize(dt):
-        dt = dt.strip()
-        if not dt or dt == "..":
-            return ".."
-        dt_obj = rfc3339_str_to_datetime(dt)
-        dt_utc = dt_obj.astimezone(timezone.utc)
-        return dt_utc.strftime("%Y-%m-%dT%H:%M:%SZ")
-
     if not isinstance(date_str, str):
         return "../.."
+
+    # If it's already a range with "..", return as-is to preserve precision
+    if "/" in date_str and ".." in date_str:
+        return (
+            date_str  # <-- PRESERVE original format like "../2025-07-16T00:24:19.000Z"
+        )
+
+    # Only apply normalization for closed ranges without ".."
     if "/" not in date_str:
-        return f"{normalize(date_str)}/{normalize(date_str)}"
+        # Single datetime - normalize with precision
+        return normalize(date_str)
+
+    # For closed ranges (start/end without ".."), normalize both parts
     try:
         start, end = date_str.split("/", 1)
+        return f"{normalize(start)}/{normalize(end)}"
     except Exception:
         return "../.."
-    return f"{normalize(start)}/{normalize(end)}"
+
+
+def normalize(dt):
+    dt = dt.strip()
+    if not dt or dt == "..":
+        return ".."
+    dt_obj = rfc3339_str_to_datetime(dt)
+    dt_utc = dt_obj.astimezone(timezone.utc)
+
+    if dt_obj.microsecond > 0:
+        return dt_utc.isoformat(timespec="milliseconds").replace("+00:00", "Z")
+    else:
+        return dt_utc.strftime("%Y-%m-%dT%H:%M:%SZ")
 
 
 # Borrowed from pystac - https://github.com/stac-utils/pystac/blob/f5e4cf4a29b62e9ef675d4a4dac7977b09f53c8f/pystac/utils.py#L370-L394