Fix intervals (#363)

* fix: typing of _to_isoformat_range

* fix: reject double open-ended intervals

* fix: allow empty strings in intervals

* chore: update changelog

Author: gadomski

CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
+- Some mishandled cases for datetime intervals [#363](https://github.com/stac-utils/pystac-client/pull/363)
+
 ### Removed
 
 - Python 3.7 support [#347](https://github.com/stac-utils/pystac-client/pull/347)

pystac_client/item_search.py

@@ -439,7 +439,7 @@ def _to_utc_isoformat(dt: datetime_) -> str:
     def _to_isoformat_range(
         self,
         component: DatetimeOrTimestamp,
-    ) -> Tuple[Optional[str], Optional[str]]:
+    ) -> Tuple[str, Optional[str]]:
         """Converts a single DatetimeOrTimestamp into one or two Datetimes.
 
         This is required to expand a single value like "2017" out to the whole
@@ -456,6 +456,8 @@ def _to_isoformat_range(
         elif isinstance(component, str):
             if component == "..":
                 return component, None
+            elif component == "":
+                return "..", None
 
             match = DATETIME_REGEX.match(component)
             if not match:
@@ -504,12 +506,16 @@ def _format_datetime(self, value: Optional[DatetimeLike]) -> Optional[Datetime]:
         if not components:
             return None
         elif len(components) == 1:
+            if components[0] is None:
+                raise Exception("cannot create a datetime query with None")
             start, end = self._to_isoformat_range(components[0])
             if end is not None:
                 return f"{start}/{end}"
             else:
                 return start
         elif len(components) == 2:
+            if all(c is None for c in components):
+                raise Exception("cannot create a double open-ended interval")
             start, _ = self._to_isoformat_range(components[0])
             backup_end, end = self._to_isoformat_range(components[1])
             return f"{start}/{end or backup_end}"

tests/test_item_search.py

@@ -254,6 +254,8 @@ def test_many_datetimes(self) -> None:
             "2020-07-23T00:00:00+03:00",
             "2020-07-23T00:00:00.000+03:00",
             "2020-07-23T00:00:00.000z",
+            "/2023-01-01T00:00:00Z",
+            "2023-01-01T00:00:00Z/",
         ]
         for date_time in datetimes:
             ItemSearch(url=SEARCH_URL, datetime=date_time)
@@ -266,6 +268,14 @@ def test_three_datetimes(self) -> None:
         with pytest.raises(Exception):
             ItemSearch(url=SEARCH_URL, datetime=[start, middle, end])
 
+    def test_double_open_ended_interval(self) -> None:
+        with pytest.raises(Exception):
+            ItemSearch(url=SEARCH_URL, datetime=[None, None])
+
+    def test_datetime_list_of_one_none(self) -> None:
+        with pytest.raises(Exception):
+            ItemSearch(url=SEARCH_URL, datetime=[None])
+
     def test_single_collection_string(self) -> None:
         # Single ID string
         search = ItemSearch(url=SEARCH_URL, collections="naip")