bpo-40025: Require _generate_next_value_ to be defined before members (GH-19098)
require `_generate_next_value_` to be defined before members
diff --git a/Lib/enum.py b/Lib/enum.py
index 0be1b60..49b552b 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -60,6 +60,7 @@
self._member_names = []
self._last_values = []
self._ignore = []
+ self._auto_called = False
def __setitem__(self, key, value):
"""Changes anything not dundered or not a descriptor.
@@ -77,6 +78,9 @@
):
raise ValueError('_names_ are reserved for future Enum use')
if key == '_generate_next_value_':
+ # check if members already defined as auto()
+ if self._auto_called:
+ raise TypeError("_generate_next_value_ must be defined before members")
setattr(self, '_generate_next_value', value)
elif key == '_ignore_':
if isinstance(value, str):
@@ -100,6 +104,7 @@
# enum overwriting a descriptor?
raise TypeError('%r already defined as: %r' % (key, self[key]))
if isinstance(value, auto):
+ self._auto_called = True
if value.value == _auto_null:
value.value = self._generate_next_value(key, 1, len(self._member_names), self._last_values[:])
value = value.value
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index ec1cfea..1df0313 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -1751,6 +1751,16 @@
self.assertEqual(Color.blue.value, 2)
self.assertEqual(Color.green.value, 3)
+ def test_auto_order(self):
+ with self.assertRaises(TypeError):
+ class Color(Enum):
+ red = auto()
+ green = auto()
+ blue = auto()
+ def _generate_next_value_(name, start, count, last):
+ return name
+
+
def test_duplicate_auto(self):
class Dupes(Enum):
first = primero = auto()