MNT: Handle GLOWS empty hist and/or DE packets (#2432)

There may be no DE and/or hist packets returned after decomming
the data, so we should gate the subsequent function calls to
make sure that we are only processing when necessary.

Author: greglucas

imap_processing/glows/l1a/glows_l1a.py

@@ -57,18 +57,17 @@ def glows_l1a(packet_filepath: Path) -> list[xr.Dataset]:
     # Decompose packet file into histogram, and direct event data.
     hist_l0, de_l0 = decom_packets(packet_filepath)
 
-    l1a_de = process_de_l0(de_l0)
-    l1a_hists = []
-    for hist in hist_l0:
-        l1a_hists.append(HistogramL1A(hist))
-
     # Generate CDF files for each day
     output_datasets = []
-    dataset = generate_histogram_dataset(l1a_hists, glows_attrs)
-    output_datasets.append(dataset)
-
-    dataset = generate_de_dataset(l1a_de, glows_attrs)
-    output_datasets.append(dataset)
+    if hist_l0:
+        l1a_hists = [HistogramL1A(hist) for hist in hist_l0]
+        dataset = generate_histogram_dataset(l1a_hists, glows_attrs)
+        output_datasets.append(dataset)
+
+    if de_l0:
+        l1a_de = process_de_l0(de_l0)
+        dataset = generate_de_dataset(l1a_de, glows_attrs)
+        output_datasets.append(dataset)
 
     return output_datasets
 

imap_processing/tests/glows/test_glows_l1a_data.py

@@ -2,6 +2,7 @@
 import dataclasses
 import json
 from pathlib import Path
+from unittest import mock
 
 import numpy as np
 import pandas as pd
@@ -559,3 +560,11 @@ def test_expected_hist_results(l1a_dataset):
 
         for field in compare_fields:
             assert np.array_equal(data[field], datapoint[field].data)
+
+
+@mock.patch("imap_processing.glows.l1a.glows_l1a.decom_packets")
+def test_glows_l1a_no_packet_data(decom_packets_mock):
+    # Should return empty list when no packet data is present
+    decom_packets_mock.return_value = ([], [])
+    output = glows_l1a("fake/filepath/packets.bin")
+    assert output == []