fix empty result filter for latest_version error when serach result is empty (#160)

* Fix bug in filter_for_latest_version if response was empty

---------

Co-authored-by: Shane Maloney <shane.maloney@dias.ie>

Author: nicHoch

changelog/160.bugfix.rst

@@ -0,0 +1 @@
+Fix error in `~stixpy.net.client.StixQueryResponse.filter_for_latest_version` if the result table was empty.

stixpy/net/client.py

@@ -17,20 +17,30 @@
 
 class StixQueryResponse(QueryResponse):
     def filter_for_latest_version(self, allow_uncompleted=False):
-        self["tidx"] = range(len(self))
-        grouped_res = self.group_by(
-            ["Start Time", "End Time", "Instrument", "Level", "DataType", "DataProduct", "Request ID"]
-        )
-        keep = np.zeros(len(self), dtype=bool)
-        for key, group in zip(grouped_res.groups.keys, grouped_res.groups):
-            group.sort("Ver")
-            if not allow_uncompleted:
-                incomplete = np.char.endswith(group["Ver"].data, "U")
-                keep[group[~incomplete][-1]["tidx"]] = True
-            else:
-                keep[group[-1]["tidx"]] = True
-        self.remove_column("tidx")
-        self.remove_rows(np.where(~keep))
+        r"""
+        Filter the response to only include the most recent versions of results.
+
+        Parameters
+        ----------
+        allow_uncompleted
+            Include incomplete version (e.g. V02U)
+
+        """
+        if len(self) > 0 and "Start Time" in self.columns:
+            self["_tidx"] = range(len(self))
+            grouped_res = self.group_by(
+                ["Start Time", "End Time", "Instrument", "Level", "DataType", "DataProduct", "Request ID"]
+            )
+            keep = np.zeros(len(self), dtype=bool)
+            for key, group in zip(grouped_res.groups.keys, grouped_res.groups):
+                group.sort("Ver")
+                if not allow_uncompleted:
+                    incomplete = np.char.endswith(group["Ver"].data, "U")
+                    keep[group[~incomplete][-1]["_tidx"]] = True
+                else:
+                    keep[group[-1]["_tidx"]] = True
+            self.remove_column("_tidx")
+            self.remove_rows(np.where(~keep))
 
 
 class STIXClient(GenericClient):

stixpy/net/tests/test_client.py

@@ -161,6 +161,12 @@ def test_search_version_and(clientlocal):
     assert len(res) == 5
 
 
+def test_search_latest_version_empty(clientlocal):
+    res = clientlocal.search(a.Time("2023-01-01T00:00", "2023-01-01T23:59"), a.Instrument.stix)
+    res.filter_for_latest_version()
+    assert len(res) == 0
+
+
 def test_search_latest_version(clientlocal):
     res = clientlocal.search(a.Time("2022-01-01T00:00", "2022-01-01T23:59"), a.Instrument.stix)
     res.filter_for_latest_version(allow_uncompleted=True)