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/Doc/library/enum.rst b/Doc/library/enum.rst
index eaf29cf..4b4f5eb 100644
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -273,6 +273,10 @@
the next :class:`int` in sequence with the last :class:`int` provided, but
the way it does this is an implementation detail and may change.
+.. note::
+
+ The :meth:`_generate_next_value_` method must be defined before any members.
+
Iteration
---------
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()
diff --git a/Misc/ACKS b/Misc/ACKS
index 69865fe..d4ffc36 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1240,6 +1240,7 @@
Grant Olson
Furkan Onder
Koray Oner
+Ethan Onstott
Piet van Oostrum
Tomas Oppelstrup
Jason Orendorff
diff --git a/Misc/NEWS.d/next/Library/2020-03-21-05-26-38.bpo-40025.DTLtyq.rst b/Misc/NEWS.d/next/Library/2020-03-21-05-26-38.bpo-40025.DTLtyq.rst
new file mode 100644
index 0000000..7b699de
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-03-21-05-26-38.bpo-40025.DTLtyq.rst
@@ -0,0 +1 @@
+Raise TypeError when _generate_next_value_ is defined after members. Patch by Ethan Onstott.
\ No newline at end of file