Fixed #33916 -- Added support for serialization of enum.Flag in migrations.

django/db/migrations/serializer.py

@@ -16,7 +16,7 @@
 from django.db.migrations.operations.base import Operation
 from django.db.migrations.utils import COMPILED_REGEX_TYPE, RegexObject
 from django.utils.functional import LazyObject, Promise
-from django.utils.version import get_docs_version
+from django.utils.version import PY311, get_docs_version
 
 
 class BaseSerializer:
@@ -125,8 +125,21 @@ class EnumSerializer(BaseSerializer):
     def serialize(self):
         enum_class = self.value.__class__
         module = enum_class.__module__
+        if issubclass(enum_class, enum.Flag):
+            if PY311:
+                members = list(self.value)
+            else:
+                members, __ = enum._decompose(enum_class, self.value)
+                members = reversed(members)
+        else:
+            members = (self.value,)
         return (
-            "%s.%s[%r]" % (module, enum_class.__qualname__, self.value.name),
+            " | ".join(
+                [
+                    f"{module}.{enum_class.__qualname__}[{item.name!r}]"
+                    for item in members
+                ]
+            ),
             {"import %s" % module},
         )
 

docs/topics/migrations.txt

@@ -739,7 +739,7 @@ Django can serialize the following:
 - ``datetime.date``, ``datetime.time``, and ``datetime.datetime`` instances
   (include those that are timezone-aware)
 - ``decimal.Decimal`` instances
-- ``enum.Enum`` instances
+- ``enum.Enum``  and ``enum.Flag`` instances
 - ``uuid.UUID`` instances
 - :func:`functools.partial` and :class:`functools.partialmethod` instances
   which have serializable ``func``, ``args``, and ``keywords`` values.
@@ -756,6 +756,10 @@ Django can serialize the following:
 - Any class reference (must be in module's top-level scope)
 - Anything with a custom ``deconstruct()`` method (:ref:`see below <custom-deconstruct-method>`)
 
+.. versionchanged:: 4.2
+
+    Serialization support for ``enum.Flag`` was added.
+
 Django cannot serialize:
 
 - Nested classes

tests/migrations/test_writer.py

@@ -80,6 +80,11 @@ class IntEnum(enum.IntEnum):
     B = 2
 
 
+class IntFlagEnum(enum.IntFlag):
+    A = 1
+    B = 2
+
+
 class OperationWriterTests(SimpleTestCase):
     def test_empty_signature(self):
         operation = custom_migration_operations.operations.TestOperation()
@@ -327,6 +332,29 @@ def test_serialize_enums(self):
             IntEnum.B,
             ("migrations.test_writer.IntEnum['B']", {"import migrations.test_writer"}),
         )
+        self.assertSerializedResultEqual(
+            IntFlagEnum.A,
+            (
+                "migrations.test_writer.IntFlagEnum['A']",
+                {"import migrations.test_writer"},
+            ),
+        )
+        self.assertSerializedResultEqual(
+            IntFlagEnum.B,
+            (
+                "migrations.test_writer.IntFlagEnum['B']",
+                {"import migrations.test_writer"},
+            ),
+        )
+        self.assertSerializedResultEqual(
+            IntFlagEnum.A | IntFlagEnum.B,
+            (
+                "migrations.test_writer.IntFlagEnum['A'] | "
+                "migrations.test_writer.IntFlagEnum['B']",
+                {"import migrations.test_writer"},
+            ),
+        )
+
         self.assertSerializedResultEqual(
             self.NestedEnum.A,
             (