Anticipate filehandler sorting in GEOSegmentYAMLReader to have sorted handlers also with pad_data=False

satpy/readers/yaml_reader.py

@@ -1157,7 +1157,13 @@ class GEOSegmentYAMLReader(GEOFlippableFileYAMLReader):
     """
 
     def create_filehandlers(self, filenames, fh_kwargs=None):
-        """Create file handler objects and determine expected segments for each."""
+        """Create file handler objects and determine expected segments for each.
+
+        Additionally, sort the filehandlers by segment number to avoid
+        issues with filenames where start_time or alphabetic sorting does not
+        produce the correct order.
+
+        """
         created_fhs = super(GEOSegmentYAMLReader, self).create_filehandlers(
             filenames, fh_kwargs=fh_kwargs)
 
@@ -1171,8 +1177,16 @@ def create_filehandlers(self, filenames, fh_kwargs=None):
                 # add segment key-values for FCI filehandlers
                 if "segment" not in fh.filename_info:
                     fh.filename_info["segment"] = fh.filename_info.get("count_in_repeat_cycle", 1)
+
+        self._sort_segment_filehandler_by_segment_number()
         return created_fhs
 
+    def _sort_segment_filehandler_by_segment_number(self):
+        if hasattr(self, "file_handlers"):
+            for file_type in self.file_handlers.keys():
+                self.file_handlers[file_type] = sorted(self.file_handlers[file_type],
+                                                       key=lambda x: x.filename_info.get("segment", 0))
+
     def _load_dataset(self, dsid, ds_info, file_handlers, dim="y", pad_data=True):
         """Load only a piece of the dataset."""
         if not pad_data:
@@ -1322,11 +1336,9 @@ def _find_missing_segments(file_handlers, ds_info, dsid):
     failure = True
     counter = 1
     expected_segments = 1
-    # get list of file handlers in segment order
-    # (ex. first segment, second segment, etc)
-    handlers = sorted(file_handlers, key=lambda x: x.filename_info.get("segment", 1))
+
     projectable = None
-    for fh in handlers:
+    for fh in file_handlers:
         if fh.filetype_info["file_type"] in ds_info["file_type"]:
             expected_segments = fh.filetype_info["expected_segments"]
 

satpy/tests/test_yaml_reader.py

@@ -971,10 +971,11 @@ def _create_mocked_fh_and_areadef(aex, ashape, expected_segments, segment, chk_p
     get_segment_position_info = MagicMock()
     get_segment_position_info.return_value = chk_pos_info
 
-    fh = MagicMock()
     filetype_info = {"expected_segments": expected_segments,
                      "file_type": "filetype1"}
     filename_info = {"segment": segment}
+
+    fh = _create_mocked_basic_fh()
     fh.filetype_info = filetype_info
     fh.filename_info = filename_info
     fh.get_area_def = get_area_def
@@ -983,6 +984,12 @@ def _create_mocked_fh_and_areadef(aex, ashape, expected_segments, segment, chk_p
     return fh, seg_area
 
 
+def _create_mocked_basic_fh():
+    fake_fh = MagicMock()
+    fake_fh.filename_info = {}
+    fake_fh.filetype_info = {}
+    return fake_fh
+
 class TestGEOSegmentYAMLReader(unittest.TestCase):
     """Test GEOSegmentYAMLReader."""
 
@@ -993,9 +1000,7 @@ def test_get_expected_segments(self, cfh):
         from satpy.readers.yaml_reader import GEOSegmentYAMLReader
         reader = GEOSegmentYAMLReader()
 
-        fake_fh = MagicMock()
-        fake_fh.filename_info = {}
-        fake_fh.filetype_info = {}
+        fake_fh = _create_mocked_basic_fh()
         cfh.return_value = {"ft1": [fake_fh]}
 
         # default (1)
@@ -1030,6 +1035,28 @@ def test_get_expected_segments(self, cfh):
         es = created_fhs["ft1"][0].filename_info["segment"]
         assert es == 5
 
+    @patch.object(yr.FileYAMLReader, "__init__", lambda x: None)
+    @patch.object(yr.FileYAMLReader, "create_filehandlers")
+    def test_segments_sorting(self, cfh):
+        """Test that segment filehandlers are sorted by segment number."""
+        from satpy.readers.yaml_reader import GEOSegmentYAMLReader
+        reader = GEOSegmentYAMLReader()
+
+        # create filehandlers with different segment numbers
+        fake_fh_1 = _create_mocked_basic_fh()
+        fake_fh_1.filename_info["segment"] = 1
+        fake_fh_2 = _create_mocked_basic_fh()
+        fake_fh_2.filename_info["segment"] = 2
+        fake_fh_3 = _create_mocked_basic_fh()
+        fake_fh_3.filename_info["segment"] = 3
+
+        # put the filehandlers in an unsorted order
+        reader.file_handlers = {"ft1": [fake_fh_1, fake_fh_3, fake_fh_2]}
+
+        # check that the created filehandlers are sorted by segment number
+        reader.create_filehandlers(["fake.nc"])
+        assert [fh.filename_info["segment"] for fh in reader.file_handlers["ft1"]] == [1, 2, 3]
+
     @patch.object(yr.FileYAMLReader, "__init__", lambda x: None)
     @patch("satpy.readers.yaml_reader.FileYAMLReader._load_dataset")
     @patch("satpy.readers.yaml_reader.xr")