Drop the deprecated Attribute.cmp (#939)

* Drop the deprecated Attribute.cmp

This has nothing to do with the cmp argument to attr.s/define which have been
undeprecated.

* Add newsfragment

* Add test for attr.ib(cmp=)

changelog.d/939.breaking.rst

@@ -0,0 +1,2 @@
+The deprecated ``cmp`` attribute of ``attrs.Attribute`` has been removed.
+This does not affect the *cmp* argument to ``attr.s`` that can be used as a shortcut to set *eq* and *order* at the same time.

src/attr/_make.py

@@ -1,11 +1,9 @@
 # SPDX-License-Identifier: MIT
 
-
 import copy
 import linecache
 import sys
 import typing
-import warnings
 
 from operator import itemgetter
 
@@ -1093,12 +1091,6 @@ def _add_method_dunders(self, method):
         return method
 
 
-_CMP_DEPRECATION = (
-    "The usage of `cmp` is deprecated and will be removed on or after "
-    "2021-06-01.  Please use `eq` and `order` instead."
-)
-
-
 def _determine_attrs_eq_order(cmp, eq, order, default_eq):
     """
     Validate the combination of *cmp*, *eq*, and *order*. Derive the effective
@@ -2594,15 +2586,6 @@ def from_counting_attr(cls, name, ca, type=None):
             **inst_dict
         )
 
-    @property
-    def cmp(self):
-        """
-        Simulate the presence of a cmp attribute and warn.
-        """
-        warnings.warn(_CMP_DEPRECATION, DeprecationWarning, stacklevel=2)
-
-        return self.eq and self.order
-
     # Don't use attr.evolve since fields(Attribute) doesn't work
     def evolve(self, **changes):
         """

tests/test_functional.py

@@ -12,7 +12,7 @@
 
 import pytest
 
-from hypothesis import assume, given
+from hypothesis import given
 from hypothesis.strategies import booleans
 
 import attr
@@ -21,8 +21,6 @@
 from attr._make import NOTHING, Attribute
 from attr.exceptions import FrozenInstanceError
 
-from .strategies import optional_bool
-
 
 @attr.s
 class C1:
@@ -643,44 +641,19 @@ class C:
 
         assert ei.value.args[0] in possible_errors
 
-    @given(cmp=optional_bool, eq=optional_bool, order=optional_bool)
-    def test_cmp_deprecated_attribute(self, cmp, eq, order):
+    @pytest.mark.parametrize("slots", [True, False])
+    @pytest.mark.parametrize("cmp", [True, False])
+    def test_attrib_cmp_shortcut(self, slots, cmp):
         """
-        Accessing Attribute.cmp raises a deprecation warning but returns True
-        if cmp is True, or eq and order are *both* effectively True.
+        Setting cmp on `attr.ib`s sets both eq and order.
         """
-        # These cases are invalid and raise a ValueError.
-        assume(cmp is None or (eq is None and order is None))
-        assume(not (eq is False and order is True))
-
-        if cmp is not None:
-            rv = cmp
-        elif eq is True or eq is None:
-            rv = order is None or order is True
-        elif cmp is None and eq is None and order is None:
-            rv = True
-        elif cmp is None or eq is None:
-            rv = False
-        else:
-            pytest.fail(
-                "Unexpected state: cmp=%r eq=%r order=%r" % (cmp, eq, order)
-            )
-
-        with pytest.deprecated_call() as dc:
-
-            @attr.s
-            class C:
-                x = attr.ib(cmp=cmp, eq=eq, order=order)
 
-            assert rv == attr.fields(C).x.cmp
-
-        (w,) = dc.list
+        @attr.s(slots=slots)
+        class C:
+            x = attr.ib(cmp=cmp)
 
-        assert (
-            "The usage of `cmp` is deprecated and will be removed on or after "
-            "2021-06-01.  Please use `eq` and `order` instead."
-            == w.message.args[0]
-        )
+        assert cmp is attr.fields(C).x.eq
+        assert cmp is attr.fields(C).x.order
 
     @pytest.mark.parametrize("slots", [True, False])
     def test_no_setattr_if_validate_without_validators(self, slots):