Fix ImportMapping.is_pivoted()

Mappings are not pivoted when only the leaf mapping has position
set to header.

Re spine-tools/Spine-Toolbox#2224

spinedb_api/import_mapping/import_mapping.py

@@ -280,7 +280,7 @@ def is_constant(self):
     def is_pivoted(self):
         if is_pivoted(self.position):
             return True
-        if self.position == Position.header and self.value is None:
+        if self.position == Position.header and self.value is None and self.child is not None:
             return True
         if self.child is None:
             return False

tests/import_mapping/test_import_mapping.py

@@ -26,6 +26,7 @@
     IndexNameMapping,
     ParameterValueIndexMapping,
     ExpandedParameterValueMapping,
+    ParameterValueMapping,
     ParameterValueTypeMapping,
     ParameterDefaultValueTypeMapping,
     DefaultValueIndexNameMapping,
@@ -2096,5 +2097,23 @@ def test_child_mapping_without_filter_doesnt_have_filter(self):
         self.assertFalse(mapping.has_filter())
 
 
+class TestIsPivoted(unittest.TestCase):
+    def test_pivoted_position_returns_true(self):
+        mapping = AlternativeMapping(-1)
+        self.assertTrue(mapping.is_pivoted())
+
+    def test_recursively_returns_false_when_all_mappings_are_non_pivoted(self):
+        mapping = unflatten([AlternativeMapping(0), ParameterValueMapping(1)])
+        self.assertFalse(mapping.is_pivoted())
+
+    def test_returns_true_when_position_is_header_and_has_child(self):
+        mapping = unflatten([AlternativeMapping(Position.header), ParameterValueMapping(0)])
+        self.assertTrue(mapping.is_pivoted())
+
+    def test_returns_false_when_position_is_header_and_is_leaf(self):
+        mapping = unflatten([AlternativeMapping(0), ParameterValueMapping(Position.header)])
+        self.assertFalse(mapping.is_pivoted())
+
+
 if __name__ == "__main__":
     unittest.main()

tests/test_mapping.py

@@ -38,6 +38,15 @@ def test_non_pivoted_columns_when_non_tail_mapping_is_pivoted(self):
         root_mapping = unflatten([Mapping(5), Mapping(Position.hidden), Mapping(-1), Mapping(13), Mapping(23)])
         self.assertEqual(root_mapping.non_pivoted_columns(), [5, 13])
 
+    def test_is_pivoted_returns_true_when_position_is_pivoted(self):
+        mapping = Mapping(-1)
+        self.assertTrue(mapping.is_pivoted())
+
+    def test_is_pivoted_returns_false_when_all_mappings_are_non_pivoted(self):
+        mappings = [Mapping(0), Mapping(1)]
+        root = unflatten(mappings)
+        self.assertFalse(root.is_pivoted())
+
 
 if __name__ == "__main__":
     unittest.main()