Map OpenAPI Discriminator mapping's values to their real value in enums

src/datamodel_code_generator/parser/base.py

@@ -1521,17 +1521,33 @@ def _create_discriminator_data_type(
     ) -> DataType:
         """Create a data type for discriminator field, using enum literals if available."""
         if enum_source:
-            enum_class_name = enum_source.reference.short_name
-            enum_member_literals: list[tuple[str, str]] = []
-            for value in discriminator_values:
-                member = enum_source.find_member(value)
-                if member and member.field.name:
-                    enum_member_literals.append((enum_class_name, member.field.name))
-                else:  # pragma: no cover
-                    enum_member_literals.append((enum_class_name, str(value)))
-            data_type = self.data_type(enum_member_literals=enum_member_literals)
-            if enum_source.module_path != discriminator_model.module_path:  # pragma: no cover
-                imports.append(Import.from_full_path(enum_source.name))
+            if self.use_enum_values_in_discriminator:
+                enum_class_name = enum_source.reference.short_name
+                enum_member_literals: list[tuple[str, DiscriminatorValue]] = []
+                for value in discriminator_values:
+                    member = enum_source.find_member(value)
+                    if member and member.field.name:
+                        enum_member_literals.append((enum_class_name, member.field.name))
+                    else:  # pragma: no cover
+                        enum_member_literals.append((enum_class_name, str(value)))
+                data_type = self.data_type(enum_member_literals=enum_member_literals)
+                if enum_source.module_path != discriminator_model.module_path:  # pragma: no cover
+                    imports.append(Import.from_full_path(enum_source.name))
+            else:
+                # According to OpenAPI specification, mapping discriminators are always string values.
+                # However, if the mapped object is an enum, we want to use the real enum value instead of
+                # the string value.
+                # See: https://swagger.io/specification/#options-for-mapping-values-to-schemas
+                # Fix: https://github.com/koxudaxi/datamodel-code-generator/issues/3073
+                for i, value in enumerate(discriminator_values):
+                    if member := enum_source.find_member(value):
+                        match member.field.default:
+                            case str():
+                                discriminator_values[i] = member.field.default.strip("'\"")
+                            case _ if isinstance(member.field.default, DiscriminatorValue):
+                                discriminator_values[i] = member.field.default
+
+                data_type = self.data_type(literals=discriminator_values)
         else:
             data_type = self.data_type(literals=discriminator_values)
         return data_type
@@ -1637,28 +1653,27 @@ def get_discriminator_field_value(
                         raise RuntimeError(msg)
 
                     enum_from_base: Enum | None = None
-                    if self.use_enum_values_in_discriminator:
-                        for base_class in discriminator_model.base_classes:
-                            if not base_class.reference or not base_class.reference.source:  # pragma: no cover
-                                continue
-                            base_model = base_class.reference.source
-                            if not isinstance(  # pragma: no cover
-                                base_model,
-                                (
-                                    pydantic_model_v2.BaseModel,
-                                    dataclass_model.DataClass,
-                                    msgspec_model.Struct,
-                                ),
-                            ):
+                    for base_class in discriminator_model.base_classes:
+                        if not base_class.reference or not base_class.reference.source:  # pragma: no cover
+                            continue
+                        base_model = base_class.reference.source
+                        if not isinstance(  # pragma: no cover
+                            base_model,
+                            (
+                                pydantic_model_v2.BaseModel,
+                                dataclass_model.DataClass,
+                                msgspec_model.Struct,
+                            ),
+                        ):
+                            continue
+                        for base_field in base_model.fields:  # pragma: no branch
+                            if field_name not in {base_field.original_name, base_field.name}:  # pragma: no cover
                                 continue
-                            for base_field in base_model.fields:  # pragma: no branch
-                                if field_name not in {base_field.original_name, base_field.name}:  # pragma: no cover
-                                    continue
-                                enum_from_base = base_field.data_type.find_source(Enum)
-                                if enum_from_base:  # pragma: no branch
-                                    break
+                            enum_from_base = base_field.data_type.find_source(Enum)
                             if enum_from_base:  # pragma: no branch
                                 break
+                        if enum_from_base:  # pragma: no branch
+                            break
 
                     has_one_literal = False
                     for discriminator_field in discriminator_model.fields:
@@ -1690,11 +1705,7 @@ def get_discriminator_field_value(
                             discriminator_field.extras["is_classvar"] = True
                             break
 
-                        enum_source: Enum | None = None
-                        if self.use_enum_values_in_discriminator:
-                            enum_source = (  # pragma: no cover
-                                discriminator_field.data_type.find_source(Enum) or enum_from_base
-                            )
+                        enum_source = discriminator_field.data_type.find_source(Enum) or enum_from_base
 
                         for field_data_type in discriminator_field.data_type.all_data_types:
                             if field_data_type.reference:  # pragma: no cover

tests/data/expected/main/openapi/discriminator/integer_mapping.py

@@ -20,10 +20,11 @@ class Foo(BaseModel):
 
 class Kind1(IntEnum):
     integer_2 = 2
+    integer_3 = 3
 
 
 class Bar(BaseModel):
-    kind: Literal[2]
+    kind: Literal[2, 3]
 
 
 class Base(RootModel[Foo | Bar]):

tests/data/openapi/discriminator_integer_mapping.yaml

@@ -14,6 +14,7 @@ components:
         mapping:
           '1': '#/components/schemas/Foo'
           '2': '#/components/schemas/Bar'
+          '3': '#/components/schemas/Bar'
     Foo:
       type: object
       properties:
@@ -30,5 +31,6 @@ components:
           type: integer
           enum:
             - 2
+            - 3
       required:
         - kind