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-rw-r--r--Lib/enum.py20
-rw-r--r--Lib/test/test_enum.py33
-rw-r--r--Misc/NEWS.d/next/Library/2018-09-11-15-49-09.bpo-34536.3IPIH5.rst2
3 files changed, 54 insertions, 1 deletions
diff --git a/Lib/enum.py b/Lib/enum.py
index 0839671cca..02405c865b 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -585,7 +585,25 @@ class Enum(metaclass=EnumMeta):
if member._value_ == value:
return member
# still not found -- try _missing_ hook
- return cls._missing_(value)
+ try:
+ exc = None
+ result = cls._missing_(value)
+ except Exception as e:
+ exc = e
+ result = None
+ if isinstance(result, cls):
+ return result
+ else:
+ ve_exc = ValueError("%r is not a valid %s" % (value, cls.__name__))
+ if result is None and exc is None:
+ raise ve_exc
+ elif exc is None:
+ exc = TypeError(
+ 'error in %s._missing_: returned %r instead of None or a valid member'
+ % (cls.__name__, result)
+ )
+ exc.__context__ = ve_exc
+ raise exc
def _generate_next_value_(name, start, count, last_values):
for last_value in reversed(last_values):
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index c04d03f375..b8efb835ce 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -3,6 +3,7 @@ import inspect
import pydoc
import sys
import unittest
+import sys
import threading
from collections import OrderedDict
from enum import Enum, IntEnum, EnumMeta, Flag, IntFlag, unique, auto
@@ -1697,6 +1698,38 @@ class TestEnum(unittest.TestCase):
third = auto()
self.assertEqual([Dupes.first, Dupes.second, Dupes.third], list(Dupes))
+ def test_missing(self):
+ class Color(Enum):
+ red = 1
+ green = 2
+ blue = 3
+ @classmethod
+ def _missing_(cls, item):
+ if item == 'three':
+ return cls.blue
+ elif item == 'bad return':
+ # trigger internal error
+ return 5
+ elif item == 'error out':
+ raise ZeroDivisionError
+ else:
+ # trigger not found
+ return None
+ self.assertIs(Color('three'), Color.blue)
+ self.assertRaises(ValueError, Color, 7)
+ try:
+ Color('bad return')
+ except TypeError as exc:
+ self.assertTrue(isinstance(exc.__context__, ValueError))
+ else:
+ raise Exception('Exception not raised.')
+ try:
+ Color('error out')
+ except ZeroDivisionError as exc:
+ self.assertTrue(isinstance(exc.__context__, ValueError))
+ else:
+ raise Exception('Exception not raised.')
+
class TestOrder(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/Library/2018-09-11-15-49-09.bpo-34536.3IPIH5.rst b/Misc/NEWS.d/next/Library/2018-09-11-15-49-09.bpo-34536.3IPIH5.rst
new file mode 100644
index 0000000000..be45eb57ca
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-09-11-15-49-09.bpo-34536.3IPIH5.rst
@@ -0,0 +1,2 @@
+`Enum._missing_`: raise `ValueError` if None returned and `TypeError` if
+non-member is returned.