bpo-40025: Require _generate_next_value_ to be defined before members(GH-19763)
require `_generate_next_value_` to be defined before members
diff --git a/Lib/enum.py b/Lib/enum.py
index 108d389..14cc00e 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