From 8a9aee71268c77867d3cc96d43cbbdcbe8c0e1e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Mon, 24 Mar 2025 10:31:24 +0100
Subject: [PATCH] [3.12] gh-131045: [Enum] fix flag containment checks when
 using values (GH-131053) (#131232)

* gh-131045: [Enum] fix flag containment checks when using values (GH-131053)

Check would fail if value would create a pseudo-member, but that member
had not yet been created.  We now attempt to create a pseudo-member for
a passed-in value first.

---------

Co-authored-by: Ethan Furman <ethan@stoneleaf.us>
Co-authored-by: Tomas R. <tomas.roun8@gmail.com>
---
 Lib/enum.py                                                | 7 ++++++-
 Lib/test/test_enum.py                                      | 2 ++
 .../Library/2025-03-10-12-26-56.gh-issue-131045.s1TssJ.rst | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-03-10-12-26-56.gh-issue-131045.s1TssJ.rst

diff --git a/Lib/enum.py b/Lib/enum.py
index eaa517e2fbc..c87aeef7157 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -771,10 +771,15 @@ class EnumType(type):
         `value` is in `cls` if:
         1) `value` is a member of `cls`, or
         2) `value` is the value of one of the `cls`'s members.
+        3) `value` is a pseudo-member (flags)
         """
         if isinstance(value, cls):
             return True
-        return value in cls._value2member_map_ or value in cls._unhashable_values_
+        try:
+            cls(value)
+            return True
+        except ValueError:
+            return value in cls._unhashable_values_
 
     def __delattr__(cls, attr):
         # nicer error message when someone tries to delete an attribute
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 2e50ae0fe96..a606002ffe9 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -422,6 +422,7 @@ class _EnumTests:
             self.assertEqual(str(TE), "<flag 'MainEnum'>")
             self.assertEqual(format(TE), "<flag 'MainEnum'>")
             self.assertTrue(TE(5) is self.dupe2)
+            self.assertTrue(7 in TE)
         else:
             self.assertEqual(repr(TE), "<enum 'MainEnum'>")
             self.assertEqual(str(TE), "<enum 'MainEnum'>")
@@ -4848,6 +4849,7 @@ class Color(enum.Enum)
  |      `value` is in `cls` if:
  |      1) `value` is a member of `cls`, or
  |      2) `value` is the value of one of the `cls`'s members.
+ |      3) `value` is a pseudo-member (flags)
  |
  |  __getitem__(name)
  |      Return the member matching `name`.
diff --git a/Misc/NEWS.d/next/Library/2025-03-10-12-26-56.gh-issue-131045.s1TssJ.rst b/Misc/NEWS.d/next/Library/2025-03-10-12-26-56.gh-issue-131045.s1TssJ.rst
new file mode 100644
index 00000000000..b6aa07276bb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-03-10-12-26-56.gh-issue-131045.s1TssJ.rst
@@ -0,0 +1 @@
+Fix issue with ``__contains__``, values, and pseudo-members for :class:`enum.Flag`.