From 5220bdfe7f0b2c4789a7b51587994207cb163f6b Mon Sep 17 00:00:00 2001
From: Saif Modan <185626776+saifmodan2006@users.noreply.github.com>
Date: Tue, 13 Oct 2026 14:34:54 +0530
Subject: [PATCH] fix(marshmallow): serialize OneOf and Equal validator choices
 to OpenAPI enum (fixes #679)

---
 .../ext/marshmallow/field_converter.py        | 40 ++++++++++++----
 tests/test_ext_marshmallow_field.py           | 46 +++++++++++++++++++
 2 files changed, 77 insertions(+), 9 deletions(-)

diff --git a/src/apispec/ext/marshmallow/field_converter.py b/src/apispec/ext/marshmallow/field_converter.py
index 6fd76a63..a191b33d 100644
--- a/src/apispec/ext/marshmallow/field_converter.py
+++ b/src/apispec/ext/marshmallow/field_converter.py
@@ -232,6 +232,21 @@ def field2default(
                 ret["default"] = default
         return ret
 
+    def _serialize_choice(
+        self, field: marshmallow.fields.Field, choice: typing.Any
+    ) -> typing.Any:
+        if choice is None:
+            return None
+        target_field = (
+            field.inner if isinstance(field, marshmallow.fields.List) else field
+        )
+        try:
+            val = target_field._serialize(choice, None, None)
+            hash(val)
+            return val
+        except Exception:
+            return choice
+
     def field2choices(
         self, field: marshmallow.fields.Field, **kwargs: typing.Any
     ) -> dict:
@@ -245,9 +260,15 @@ def field2choices(
         choices = []
         for validator in field.validators:
             if hasattr(validator, "choices"):
-                choices.append(OrderedSet(validator.choices))
+                choices.append(
+                    OrderedSet(
+                        self._serialize_choice(field, c) for c in validator.choices
+                    )
+                )
             elif hasattr(validator, "comparable"):
-                choices.append(OrderedSet([validator.comparable]))
+                choices.append(
+                    OrderedSet([self._serialize_choice(field, validator.comparable)])
+                )
         if choices:
             attributes["enum"] = list(functools.reduce(operator.and_, choices))
 
@@ -550,13 +571,14 @@ def enum2properties(self, field, **kwargs: typing.Any) -> dict:
         ret = {}
         if isinstance(field, marshmallow.fields.Enum):
             ret = self.field2property(field.field)
-            if field.by_value is False:
-                choices = (m for m in field.enum.__members__)
-            else:
-                choices = (m.value for m in field.enum)
-            ret["enum"] = [field.field._serialize(v, None, None) for v in choices]
-            if field.allow_none and None not in ret["enum"]:
-                ret["enum"].append(None)
+            if "enum" not in kwargs.get("ret", {}):
+                if field.by_value is False:
+                    choices = (m for m in field.enum.__members__)
+                else:
+                    choices = (m.value for m in field.enum)
+                ret["enum"] = [field.field._serialize(v, None, None) for v in choices]
+                if field.allow_none and None not in ret["enum"]:
+                    ret["enum"].append(None)
         return ret
 
     def datetime2properties(self, field, **kwargs: typing.Any) -> dict:
diff --git a/tests/test_ext_marshmallow_field.py b/tests/test_ext_marshmallow_field.py
index eddb89e9..12827190 100644
--- a/tests/test_ext_marshmallow_field.py
+++ b/tests/test_ext_marshmallow_field.py
@@ -1,6 +1,7 @@
 import datetime as dt
 import importlib.metadata
 import re
+import uuid
 from enum import Enum
 
 import pytest
@@ -19,6 +20,51 @@ def test_field2choices_preserving_order(openapi):
     assert openapi.field2choices(field) == {"enum": choices}
 
 
+def test_field2choices_serializes_choices(openapi):
+    date_choices = [dt.date(2023, 1, 1), dt.date(2023, 1, 2)]
+    field = fields.Date(validate=validate.OneOf(date_choices))
+    assert openapi.field2choices(field) == {"enum": ["2023-01-01", "2023-01-02"]}
+
+    dtime_choices = [dt.datetime(2023, 1, 1, 12, 0)]
+    field = fields.DateTime(validate=validate.OneOf(dtime_choices))
+    assert openapi.field2choices(field) == {"enum": ["2023-01-01T12:00:00"]}
+
+    u = uuid.uuid4()
+    field = fields.UUID(validate=validate.OneOf([u]))
+    assert openapi.field2choices(field) == {"enum": [str(u)]}
+
+    field = fields.Date(validate=validate.Equal(dt.date(2023, 1, 1)))
+    assert openapi.field2choices(field) == {"enum": ["2023-01-01"]}
+
+
+def test_field2choices_with_labels(openapi):
+    field = fields.Integer(validate=validate.OneOf([1, 2], labels=["one", "two"]))
+    assert openapi.field2choices(field) == {"enum": [1, 2]}
+
+
+def test_enum_field_with_oneof_validator(spec_fixture):
+    class MyEnum(Enum):
+        one = 1
+        two = 2
+        three = 3
+
+    field = fields.Enum(MyEnum, validate=validate.OneOf([MyEnum.one, MyEnum.two]))
+    ret = spec_fixture.openapi.field2property(field)
+    assert ret["type"] == "string"
+    assert ret["enum"] == ["one", "two"]
+
+    field_val = fields.Enum(
+        MyEnum, by_value=True, validate=validate.OneOf([MyEnum.one, MyEnum.two])
+    )
+    ret_val = spec_fixture.openapi.field2property(field_val)
+    assert ret_val["enum"] == [1, 2]
+
+    field_eq = fields.Enum(MyEnum, validate=validate.Equal(MyEnum.two))
+    ret_eq = spec_fixture.openapi.field2property(field_eq)
+    assert ret_eq["type"] == "string"
+    assert ret_eq["enum"] == ["two"]
+
+
 @pytest.mark.parametrize(
     ("FieldClass", "jsontype"),
     [