[Python-checkins] gh-91456: [Enum] Deprecate default auto() behavior with mixed value types (GH-91457)
ethanfurman
webhook-mailer at python.org
Thu Jun 23 02:20:48 EDT 2022
https://github.com/python/cpython/commit/fb1e9506c14ef32d5bec126dad6fa769c8c054f6
commit: fb1e9506c14ef32d5bec126dad6fa769c8c054f6
branch: main
author: Oscar R <89599049+oscar-LT at users.noreply.github.com>
committer: ethanfurman <ethan at stoneleaf.us>
date: 2022-06-22T23:20:24-07:00
summary:
gh-91456: [Enum] Deprecate default auto() behavior with mixed value types (GH-91457)
When used with plain Enum, auto() returns the last numeric value assigned, skipping any incompatible member values (such as strings); starting in 3.13 the default auto() for plain Enums will require all the values to be of compatible types, and will return a new value that is 1 higher than any existing value.
Co-authored-by: Ethan Furman <ethan at stoneleaf.us>
files:
A Misc/NEWS.d/next/Library/2022-04-11-16-55-41.gh-issue-91456.DK3KKl.rst
M Doc/library/enum.rst
M Lib/enum.py
M Lib/test/test_enum.py
diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst
index c3256c56c6366..b1333c7dd5cf9 100644
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -761,6 +761,10 @@ Utilities and Decorators
``_generate_next_value_`` can be overridden to customize the values used by
*auto*.
+ .. note:: in 3.13 the default ``"generate_next_value_`` will always return
+ the highest member value incremented by 1, and will fail if any
+ member is an incompatible type.
+
.. decorator:: property
A decorator similar to the built-in *property*, but specifically for
diff --git a/Lib/enum.py b/Lib/enum.py
index decb601496fc9..8d0982a218d76 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -1205,21 +1205,39 @@ def __new__(cls, value):
def __init__(self, *args, **kwds):
pass
- def _generate_next_value_(name, start, count, last_values):
+ def _generate_next_value_(name, start, count, last_value):
"""
Generate the next value when not given.
name: the name of the member
start: the initial start value or None
count: the number of existing members
- last_value: the last value assigned or None
+ last_value: the list of values assigned
"""
- for last_value in reversed(last_values):
- try:
- return last_value + 1
- except TypeError:
- pass
- else:
+ if not last_value:
+ return start
+ try:
+ last = last_value[-1]
+ last_value.sort()
+ if last == last_value[-1]:
+ # no difference between old and new methods
+ return last + 1
+ else:
+ # trigger old method (with warning)
+ raise TypeError
+ except TypeError:
+ import warnings
+ warnings.warn(
+ "In 3.13 the default `auto()`/`_generate_next_value_` will require all values to be sortable and support adding +1\n"
+ "and the value returned will be the largest value in the enum incremented by 1",
+ DeprecationWarning,
+ stacklevel=3,
+ )
+ for v in last_value:
+ try:
+ return v + 1
+ except TypeError:
+ pass
return start
@classmethod
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index e26ef000ea76c..528ec0de47d7a 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -3953,23 +3953,54 @@ class Color(AutoNameEnum):
self.assertEqual(Color.blue.value, 'blue')
self.assertEqual(Color.green.value, 'green')
- def test_auto_garbage(self):
- class Color(Enum):
- red = 'red'
- blue = auto()
+ @unittest.skipIf(
+ python_version >= (3, 13),
+ 'mixed types with auto() no longer supported',
+ )
+ def test_auto_garbage_ok(self):
+ with self.assertWarnsRegex(DeprecationWarning, 'will require all values to be sortable'):
+ class Color(Enum):
+ red = 'red'
+ blue = auto()
self.assertEqual(Color.blue.value, 1)
- def test_auto_garbage_corrected(self):
- class Color(Enum):
- red = 'red'
- blue = 2
- green = auto()
+ @unittest.skipIf(
+ python_version >= (3, 13),
+ 'mixed types with auto() no longer supported',
+ )
+ def test_auto_garbage_corrected_ok(self):
+ with self.assertWarnsRegex(DeprecationWarning, 'will require all values to be sortable'):
+ class Color(Enum):
+ red = 'red'
+ blue = 2
+ green = auto()
self.assertEqual(list(Color), [Color.red, Color.blue, Color.green])
self.assertEqual(Color.red.value, 'red')
self.assertEqual(Color.blue.value, 2)
self.assertEqual(Color.green.value, 3)
+ @unittest.skipIf(
+ python_version < (3, 13),
+ 'mixed types with auto() will raise in 3.13',
+ )
+ def test_auto_garbage_fail(self):
+ with self.assertRaisesRegex(TypeError, 'will require all values to be sortable'):
+ class Color(Enum):
+ red = 'red'
+ blue = auto()
+
+ @unittest.skipIf(
+ python_version < (3, 13),
+ 'mixed types with auto() will raise in 3.13',
+ )
+ def test_auto_garbage_corrected_fail(self):
+ with self.assertRaisesRegex(TypeError, 'will require all values to be sortable'):
+ class Color(Enum):
+ red = 'red'
+ blue = 2
+ green = auto()
+
def test_auto_order(self):
with self.assertRaises(TypeError):
class Color(Enum):
@@ -3991,6 +4022,22 @@ def _generate_next_value_(name, start, count, last):
self.assertEqual(Color.red.value, 'pathological case')
self.assertEqual(Color.blue.value, 'blue')
+ @unittest.skipIf(
+ python_version < (3, 13),
+ 'auto() will return highest value + 1 in 3.13',
+ )
+ def test_auto_with_aliases(self):
+ class Color(Enum):
+ red = auto()
+ blue = auto()
+ oxford = blue
+ crimson = red
+ green = auto()
+ self.assertIs(Color.crimson, Color.red)
+ self.assertIs(Color.oxford, Color.blue)
+ self.assertIsNot(Color.green, Color.red)
+ self.assertIsNot(Color.green, Color.blue)
+
def test_duplicate_auto(self):
class Dupes(Enum):
first = primero = auto()
diff --git a/Misc/NEWS.d/next/Library/2022-04-11-16-55-41.gh-issue-91456.DK3KKl.rst b/Misc/NEWS.d/next/Library/2022-04-11-16-55-41.gh-issue-91456.DK3KKl.rst
new file mode 100644
index 0000000000000..a4c853149bdf0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-04-11-16-55-41.gh-issue-91456.DK3KKl.rst
@@ -0,0 +1,3 @@
+Deprecate current default auto() behavior: In 3.13 the default will be for
+for auto() to always return the largest member value incremented by
+1, and to raise if incompatible value types are used.
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