Add test coverage for optimization of Relay nodes

Author: tpict

tests/test_query.py

@@ -520,3 +520,40 @@ def test_should_only_use_the_only_and_not_select_related():
     items = gql_optimizer.query(qs, info)
     optimized_items = qs.only('id', 'name')
     assert_query_equality(items, optimized_items)
+
+@pytest.mark.django_db
+def test_should_use_only_with_node_interface():
+    info = create_resolve_info(schema, '''
+        query {
+            relayItems {
+                edges {
+                    node {
+                        id
+                    }
+                }
+            }
+        }
+    ''')
+    qs = Item.objects.all()
+    items = gql_optimizer.query(qs, info)
+    optimized_items = qs.only('id')
+    assert_query_equality(items, optimized_items)
+
+@pytest.mark.django_db
+def test_should_not_try_to_optimize_non_field_model_fields_on_relay_node():
+    info = create_resolve_info(schema, '''
+        query {
+            relayItems {
+                edges {
+                    node {
+                        id
+                        foo
+                    }
+                }
+            }
+        }
+    ''')
+    qs = Item.objects.all()
+    items = gql_optimizer.query(qs, info)
+    optimized_items = qs
+    assert_query_equality(items, optimized_items)