handle datasets with one column only

random_sets/datasources.py

@@ -124,6 +124,7 @@ class DataSource:
         # If there is no data for the specified option, stop now.
         flattened = []
         if not self.data[option]:
+            return [option]
             raise ValueError(f"There is no data for '{option}' in your data source.")
 
         if hasattr(self.data[option], 'keys'):

test/test_datasources.py

@@ -56,6 +56,19 @@ def test_zero_frequency():
         assert 'Option 1' not in val
 
 
+def test_one_column_only():
+    fixture = StringIO(f"""
+{fixture_metadata}
+Option 1:
+Option 2:
+Option 3:
+""")
+    ds = datasources.DataSource(fixture)
+    vals = ds.random_values(count=10)
+    assert len(vals) == 10
+    assert len(vals[0]) == 1
+
+
 def test_distribution_accuracy_to_one_decimal_place():
     fixture = StringIO(fixture_metadata + fixture_source)
     ds = datasources.DataSource(fixture)