Fix usage of intersection/union for OrderedSet in Nested field (#1627)

* Add basic set methods to OrderedSet

Add `union`, `intersection` and `difference` methods to `OrderedSet`.

This fixes a bug where a `Nested` field initialized with an instance of a schema (instead of a class) would fail to set the `only` property when serializing.

* Parametrize OrderedSet tests

* Fix issue by using set operators instead of methods

* Update changelog

Co-authored-by: Steven Loria <sloria1@gmail.com>

Author: juannorris

AUTHORS.rst

@@ -150,3 +150,4 @@ Contributors (chronological)
 - Laurie Opperman `@EpicWink <https://github.com/EpicWink>`_
 - Ram Rachum `@cool-RR <https://github.com/cool-RR>`_
 - `@weeix <https://github.com/weeix>`_
+- Juan Norris `@juannorris <https://github.com/juannorris>`_

CHANGELOG.rst

@@ -12,6 +12,11 @@ Support:
 
 - Document ``default_error_messages`` on field classes (:pr:`1619`). Thanks :user:`weeix`.
 
+Bug fixes:
+
+- Fix passing ``only`` and ``exclude`` to ``Nested`` with an ordered ``Schema`` (:pr:`1627`).
+  Thanks :user:`juannorris` for the PR.
+
 3.6.1 (2020-06-02)
 ******************
 

src/marshmallow/fields.py

@@ -522,10 +522,10 @@ def schema(self):
                         original = self._schema.only
                     else:  # only=None -> all fields
                         original = self._schema.fields.keys()
-                    self._schema.only = set_class(self.only).intersection(original)
+                    self._schema.only = set_class(self.only) & set_class(original)
                 if self.exclude:
                     original = self._schema.exclude
-                    self._schema.exclude = set_class(self.exclude).union(original)
+                    self._schema.exclude = set_class(self.exclude) | set_class(original)
                 self._schema._init_fields()
             else:
                 if isinstance(nested, type) and issubclass(nested, SchemaABC):

tests/test_fields.py

@@ -277,6 +277,24 @@ class MySchema(Schema):
             with pytest.raises(ValidationError):
                 MySchema().load({"nested": {"x": 1}})
 
+    @pytest.mark.parametrize(
+        ("param", "fields_list"), [("only", ["foo"]), ("exclude", ["bar"])]
+    )
+    def test_ordered_instanced_nested_schema_only_and_exclude(self, param, fields_list):
+        class NestedSchema(Schema):
+            foo = fields.String()
+            bar = fields.String()
+
+            class Meta:
+                ordered = True
+
+        class MySchema(Schema):
+            nested = fields.Nested(NestedSchema(), **{param: fields_list})
+
+        assert MySchema().dump({"nested": {"foo": "baz", "bar": "bax"}}) == {
+            "nested": {"foo": "baz"}
+        }
+
 
 class TestListNested:
     @pytest.mark.parametrize("param", ("only", "exclude", "dump_only", "load_only"))