Fix get_items without ids (#579)

* fix: get_items without ids

Passing empty list to `search` has different semantics than `None`.

* fix: disallow empty lists in ItemSearch

* fix: wayy overengineer _format_ids

Author: gadomski

CHANGELOG.md

@@ -14,7 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
-- Updated `get_items` signatures for PySTAC v1.8 [#559](https://github.com/stac-utils/pystac-client/pull/559)
+- Updated `get_items` signatures for PySTAC v1.8 [#559](https://github.com/stac-utils/pystac-client/pull/559), [#579](https://github.com/stac-utils/pystac-client/pull/579)
 
 ## [v0.7.2] - 2023-06-23
 

pystac_client/item_search.py

@@ -550,13 +550,18 @@ def _format(c: Any) -> Collections:
 
     @staticmethod
     def _format_ids(value: Optional[IDsLike]) -> Optional[IDs]:
-        if value is None:
+        if value is None or isinstance(value, (tuple, list)) and not value:
+            # We can't just check for truthiness here because of the Iterator[str] case
             return None
-
-        if isinstance(value, str):
-            return tuple(value.split(","))
-
-        return tuple(value)
+        elif isinstance(value, str):
+            # We could check for str in the first branch, but then we'd be checking
+            # for str twice #microoptimizations
+            if value:
+                return tuple(value.split(","))
+            else:
+                return None
+        else:
+            return tuple(value)
 
     def _format_sortby(self, value: Optional[SortbyLike]) -> Optional[Sortby]:
         if value is None: