[Python-checkins] bpo-41789: honor object overrides in Enum classes (GH-22250)

[Miss Islington (bot)]

https://github.com/python/cpython/commit/929112ef81ccef20d3aef25c8a1142059ee941da
commit: 929112ef81ccef20d3aef25c8a1142059ee941da
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-09-15T17:16:36-07:00
summary:

bpo-41789: honor object overrides in Enum classes (GH-22250)


EnumMeta double-checks that `__repr__`, `__str__`, `__format__`, and `__reduce_ex__` are not the same as `object`'s, and replaces them if they are -- even if that replacement was intentionally done in the Enum being constructed.  This patch fixes that.

Automerge-Triggered-By: @ethanfurman
(cherry picked from commit 22415ad62555d79bd583b4a7d6a96006624a8277)

Co-authored-by: Ethan Furman <ethan at stoneleaf.us>

files:
A Misc/NEWS.d/next/Library/2020-09-14-19-27-46.bpo-41789.pI_uZQ.rst
M Lib/enum.py
M Lib/test/test_enum.py

diff --git a/Lib/enum.py b/Lib/enum.py
index dfde75048b0f0..c892d738f8b38 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -249,7 +249,11 @@ def __new__(metacls, cls, bases, classdict):
 
         # double check that repr and friends are not the mixin's or various
         # things break (such as pickle)
+        # however, if the method is defined in the Enum itself, don't replace
+        # it
         for name in ('__repr__', '__str__', '__format__', '__reduce_ex__'):
+            if name in classdict:
+                continue
             class_method = getattr(enum_class, name)
             obj_method = getattr(member_type, name, None)
             enum_method = getattr(first_enum, name, None)
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 13f7ba4949fcc..32ff32cf17567 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -551,6 +551,14 @@ def test_format_enum_str(self):
         self.assertFormatIsValue('{:>20}', Directional.WEST)
         self.assertFormatIsValue('{:<20}', Directional.WEST)
 
+    def test_object_str_override(self):
+        class Colors(Enum):
+            RED, GREEN, BLUE = 1, 2, 3
+            def __repr__(self):
+                return "test.%s" % (self._name_, )
+            __str__ = object.__str__
+        self.assertEqual(str(Colors.RED), 'test.RED')
+
     def test_enum_str_override(self):
         class MyStrEnum(Enum):
             def __str__(self):
@@ -593,7 +601,6 @@ def repr(self):
             class Huh(MyStr, MyInt, Enum):
                 One = 1
 
-
     def test_hash(self):
         Season = self.Season
         dates = {}
diff --git a/Misc/NEWS.d/next/Library/2020-09-14-19-27-46.bpo-41789.pI_uZQ.rst b/Misc/NEWS.d/next/Library/2020-09-14-19-27-46.bpo-41789.pI_uZQ.rst
new file mode 100644
index 0000000000000..5ce7a3ca67b72
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-14-19-27-46.bpo-41789.pI_uZQ.rst
@@ -0,0 +1,2 @@
+Honor `object` overrides in `Enum` class creation (specifically, `__str__`,
+`__repr__`, `__format__`, and `__reduce_ex__`).