Partially code-cover &, |, -, ^ multidict operators

Specifically, this patch covers the cases of the dunder methods
returning `NotImplemented` and handling non-`Set` `Iterable`s.

It fully covers the `_viewbaseset_and()`, `_viewbaseset_or()`,
`_viewbaseset_sub()` and `_viewbaseset_xor()` functions in the
`multidict._multidict_base` module with functional tests.

Ref #921
PR #936

Signed-off-by: a5r0n <a5r0n@users.noreply.github.com>
Co-authored-by: a5r0n <a5r0n@users.noreply.github.com>
Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

CHANGES/936.contrib.rst

@@ -0,0 +1,9 @@
+Added test coverage for the :ref:`and <python:and>`, :ref:`or
+<python:or>`, :py:obj:`sub <python:object.__sub__>`, and
+:py:obj:`xor <python:object.__xor__>` operators in the
+:file:`multidict/_multidict_base.py` module. It also covers
+:py:data:`NotImplemented` and
+":py:class:`~typing.Iterable`-but-not-:py:class:`~typing.Set`"
+cases there.
+
+-- by :user:`a5r0n`

tests/test_multidict.py

@@ -12,6 +12,7 @@
     Dict,
     Iterable,
     Iterator,
+    KeysView,
     List,
     Mapping,
     Set,
@@ -391,6 +392,27 @@ def test_and2(self, cls: Type[MutableMultiMapping[str]]) -> None:
 
         assert {"key"} == {"key", "key2"} & d.keys()
 
+    def test_bitwise_and_not_implemented(
+        self, cls: Type[MutableMultiMapping[str]]
+    ) -> None:
+        d = cls([("key", "value1")])
+
+        sentinel_operation_result = object()
+
+        class RightOperand:
+            def __rand__(self, other: KeysView[str]) -> object:
+                assert isinstance(other, KeysView)
+                return sentinel_operation_result
+
+        assert d.keys() & RightOperand() is sentinel_operation_result
+
+    def test_bitwise_and_iterable_not_set(
+        self, cls: Type[MutableMultiMapping[str]]
+    ) -> None:
+        d = cls([("key", "value1")])
+
+        assert {"key"} == d.keys() & ["key", "key2"]
+
     def test_or(self, cls: Type[MutableMultiMapping[str]]) -> None:
         d = cls([("key", "value1")])
 
@@ -401,6 +423,27 @@ def test_or2(self, cls: Type[MutableMultiMapping[str]]) -> None:
 
         assert {"key", "key2"} == {"key2"} | d.keys()
 
+    def test_bitwise_or_not_implemented(
+        self, cls: Type[MutableMultiMapping[str]]
+    ) -> None:
+        d = cls([("key", "value1")])
+
+        sentinel_operation_result = object()
+
+        class RightOperand:
+            def __ror__(self, other: KeysView[str]) -> object:
+                assert isinstance(other, KeysView)
+                return sentinel_operation_result
+
+        assert d.keys() | RightOperand() is sentinel_operation_result
+
+    def test_bitwise_or_iterable_not_set(
+        self, cls: Type[MutableMultiMapping[str]]
+    ) -> None:
+        d = cls([("key", "value1")])
+
+        assert {"key", "key2"} == d.keys() | ["key2"]
+
     def test_sub(self, cls: Type[MutableMultiMapping[str]]) -> None:
         d = cls([("key", "value1"), ("key2", "value2")])
 
@@ -411,6 +454,23 @@ def test_sub2(self, cls: Type[MutableMultiMapping[str]]) -> None:
 
         assert {"key3"} == {"key", "key2", "key3"} - d.keys()
 
+    def test_sub_not_implemented(self, cls: Type[MutableMultiMapping[str]]) -> None:
+        d = cls([("key", "value1"), ("key2", "value2")])
+
+        sentinel_operation_result = object()
+
+        class RightOperand:
+            def __rsub__(self, other: KeysView[str]) -> object:
+                assert isinstance(other, KeysView)
+                return sentinel_operation_result
+
+        assert d.keys() - RightOperand() is sentinel_operation_result
+
+    def test_sub_iterable_not_set(self, cls: Type[MutableMultiMapping[str]]) -> None:
+        d = cls([("key", "value1"), ("key2", "value2")])
+
+        assert {"key"} == d.keys() - ["key2"]
+
     def test_xor(self, cls: Type[MutableMultiMapping[str]]) -> None:
         d = cls([("key", "value1"), ("key2", "value2")])
 
@@ -421,6 +481,23 @@ def test_xor2(self, cls: Type[MutableMultiMapping[str]]) -> None:
 
         assert {"key", "key3"} == {"key2", "key3"} ^ d.keys()
 
+    def test_xor_not_implemented(self, cls: Type[MutableMultiMapping[str]]) -> None:
+        d = cls([("key", "value1"), ("key2", "value2")])
+
+        sentinel_operation_result = object()
+
+        class RightOperand:
+            def __rxor__(self, other: KeysView[str]) -> object:
+                assert isinstance(other, KeysView)
+                return sentinel_operation_result
+
+        assert d.keys() ^ RightOperand() is sentinel_operation_result
+
+    def test_xor_iterable_not_set(self, cls: Type[MutableMultiMapping[str]]) -> None:
+        d = cls([("key", "value1"), ("key2", "value2")])
+
+        assert {"key", "key3"} == d.keys() ^ ["key2", "key3"]
+
     @pytest.mark.parametrize(
         ("key", "value", "expected"),
         (("key2", "v", True), ("key", "value1", False)),