Stop raising a deprecation warning on assoc (#1119)

* Stop warning about assoc & explain why

* Fix tests

src/attr/_funcs.py

@@ -316,6 +316,14 @@ def assoc(inst, **changes):
     """
     Copy *inst* and apply *changes*.
 
+    This is different from `evolve` that applies the changes to the arguments
+    that create the new instance.
+
+    `evolve`'s behavior is preferable, but there are `edge cases`_ where it
+    doesn't work. Therefore `assoc` is deprecated, but will not be removed.
+
+    .. _`edge cases`: https://github.com/python-attrs/attrs/issues/251
+
     :param inst: Instance of a class with *attrs* attributes.
     :param changes: Keyword changes in the new copy.
 
@@ -331,13 +339,6 @@ def assoc(inst, **changes):
         This function will not be removed du to the slightly different approach
         compared to `attrs.evolve`.
     """
-    import warnings
-
-    warnings.warn(
-        "assoc is deprecated and will be removed after 2018/01.",
-        DeprecationWarning,
-        stacklevel=2,
-    )
     new = copy.copy(inst)
     attrs = fields(inst.__class__)
     for k, v in changes.items():

tests/test_funcs.py

@@ -467,8 +467,7 @@ class C:
             pass
 
         i1 = C()
-        with pytest.deprecated_call():
-            i2 = assoc(i1)
+        i2 = assoc(i1)
 
         assert i1 is not i2
         assert i1 == i2
@@ -479,8 +478,7 @@ def test_no_changes(self, C):
         No changes means a verbatim copy.
         """
         i1 = C()
-        with pytest.deprecated_call():
-            i2 = assoc(i1)
+        i2 = assoc(i1)
 
         assert i1 is not i2
         assert i1 == i2
@@ -497,8 +495,7 @@ def test_change(self, C, data):
         chosen_names = data.draw(st.sets(st.sampled_from(field_names)))
         change_dict = {name: data.draw(st.integers()) for name in chosen_names}
 
-        with pytest.deprecated_call():
-            changed = assoc(original, **change_dict)
+        changed = assoc(original, **change_dict)
 
         for k, v in change_dict.items():
             assert getattr(changed, k) == v
@@ -527,22 +524,7 @@ class C:
             x = attr.ib()
             y = attr.ib()
 
-        with pytest.deprecated_call():
-            assert C(3, 2) == assoc(C(1, 2), x=3)
-
-    def test_warning(self):
-        """
-        DeprecationWarning points to the correct file.
-        """
-
-        @attr.s
-        class C:
-            x = attr.ib()
-
-        with pytest.warns(DeprecationWarning) as wi:
-            assert C(2) == assoc(C(1), x=2)
-
-        assert __file__ == wi.list[0].filename
+        assert C(3, 2) == assoc(C(1, 2), x=3)
 
 
 class TestEvolve: