add unit test for Tabular.set_meta for empty files

lib/galaxy/datatypes/tabular.py

@@ -556,13 +556,14 @@ class Tabular(TabularData):
                             comment_lines = None  # type: ignore [assignment]
                         break
                     i += 1
-
+        print(column_types)
         # we error on the larger number of columns
         # first we pad our column_types by using data from first line
         if len(first_line_column_types) > len(column_types):
             for column_type in first_line_column_types[len(column_types) :]:
                 column_types.append(column_type)
         # Now we fill any unknown (None) column_types with data from first line
+        print(column_types)
         for i in range(len(column_types)):
             if column_types[i] is None:
                 if len(first_line_column_types) <= i or first_line_column_types[i] is None:

test/unit/data/datatypes/test_tabular.py

@@ -22,3 +22,18 @@ def test_tabular_set_meta_large_file():
         assert dataset.metadata.columns == 2
         assert dataset.metadata.delimiter == "\t"
         assert not hasattr(dataset.metadata, "column_names")
+
+
+def test_tabular_set_meta_empty():
+    with tempfile.NamedTemporaryFile(mode="w") as test_file:
+        test_file.flush()
+        dataset = MockDataset(id=1)
+        dataset.file_name = test_file.name
+        Tabular().set_meta(dataset)
+        # data and comment lines are not stored if more than MAX_DATA_LINES
+        assert dataset.metadata.data_lines == 0
+        assert dataset.metadata.comment_lines == 0
+        assert dataset.metadata.column_types == []
+        assert dataset.metadata.columns == 0
+        assert dataset.metadata.delimiter == "\t"
+        assert not hasattr(dataset.metadata, "column_names")