fix: 🐛 Fix ValueError when using Flag (#2759)

* 🐛 Fix `dataclasses.field` can't be reused

* 📝 CHANGELOG.md

* Update CHANGELOG.md

Signed-off-by: Dorukyum <53639936+Dorukyum@users.noreply.github.com>

* ♻️ Move `_missing_field_factory` to flags.py and remove incorrect comment

---------

Signed-off-by: Paillat <me@paillat.dev>
Signed-off-by: Dorukyum <53639936+Dorukyum@users.noreply.github.com>
Co-authored-by: Dorukyum <53639936+Dorukyum@users.noreply.github.com>

Author: Paillat-dev

CHANGELOG.md

@@ -107,6 +107,8 @@ These changes are available on the `master` branch, but have not yet been releas
   ([#2739](https://github.com/Pycord-Development/pycord/pull/2739))
 - Fixed missing `None` type hints in `Select.__init__`.
   ([#2746](https://github.com/Pycord-Development/pycord/pull/2746))
+- Fixed `TypeError` when using `Flag` with Python 3.11+.
+  ([#2759](https://github.com/Pycord-Development/pycord/pull/2759))
 - Fixed `TypeError` when specifying `thread_name` in `Webhook.send`.
   ([#2761](https://github.com/Pycord-Development/pycord/pull/2761))
 - Updated `valid_locales` to support `in` and `es-419`.

discord/ext/commands/flags.py

@@ -31,12 +31,11 @@
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING, Any, Iterator, Literal, Pattern, TypeVar, Union
 
-from discord.utils import MISSING, MissingField, maybe_coroutine, resolve_annotation
-
-if sys.version_info >= (3, 11):
-    _MISSING = MissingField
-else:
-    _MISSING = MISSING
+from discord.utils import (
+    MISSING,
+    maybe_coroutine,
+    resolve_annotation,
+)
 
 from .converter import run_converters
 from .errors import (
@@ -59,6 +58,10 @@
     from .context import Context
 
 
+def _missing_field_factory() -> field:
+    return field(default_factory=lambda: MISSING)
+
+
 @dataclass
 class Flag:
     """Represents a flag parameter for :class:`FlagConverter`.
@@ -86,13 +89,13 @@ class Flag:
         Whether multiple given values overrides the previous value.
     """
 
-    name: str = _MISSING
+    name: str = _missing_field_factory()
     aliases: list[str] = field(default_factory=list)
-    attribute: str = _MISSING
-    annotation: Any = _MISSING
-    default: Any = _MISSING
-    max_args: int = _MISSING
-    override: bool = _MISSING
+    attribute: str = _missing_field_factory()
+    annotation: Any = _missing_field_factory()
+    default: Any = _missing_field_factory()
+    max_args: int = _missing_field_factory()
+    override: bool = _missing_field_factory()
     cast_to_dict: bool = False
 
     @property

discord/utils.py

@@ -39,7 +39,6 @@
 import warnings
 from base64 import b64encode
 from bisect import bisect_left
-from dataclasses import field
 from inspect import isawaitable as _isawaitable
 from inspect import signature as _signature
 from operator import attrgetter
@@ -115,11 +114,6 @@ def __repr__(self) -> str:
 
 
 MISSING: Any = _MissingSentinel()
-# As of 3.11, directly setting a dataclass field to MISSING causes a ValueError. Using
-# field(default=MISSING) produces the same error, but passing a lambda to
-# default_factory produces the same behavior as default=MISSING and does not raise an
-# error.
-MissingField = field(default_factory=lambda: MISSING)
 
 
 class _cached_property: