Change ordering of actions

datamodel_code_generator/parser/base.py

@@ -1370,8 +1370,8 @@ class Processed(NamedTuple):
             )
             self.__set_default_enum_member(models)
             self.__sort_models(models, imports)
-            self.__set_one_literal_on_default(models)
             self.__apply_discriminator_type(models, imports)
+            self.__set_one_literal_on_default(models)
 
             processed_models.append(
                 Processed(module, models, init, imports, scoped_model_resolver)

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

@@ -0,0 +1,32 @@
+# generated by datamodel-codegen:
+#   filename:  discriminator_enum.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import Literal, Union
+
+from pydantic import BaseModel, Field, RootModel
+
+
+class RequestVersionEnum(Enum):
+    v1 = 'v1'
+    v2 = 'v2'
+
+
+class RequestBase(BaseModel):
+    version: RequestVersionEnum
+
+
+class RequestV1(RequestBase):
+    request_id: str = Field(..., description='there is description', title='test title')
+    version: Literal['v1'] = 'v1'
+
+
+class RequestV2(RequestBase):
+    version: Literal['v2'] = 'v2'
+
+
+class Request(RootModel[Union[RequestV1, RequestV2]]):
+    root: Union[RequestV1, RequestV2] = Field(..., discriminator='version')

tests/main/openapi/test_main_openapi.py

@@ -2798,3 +2798,31 @@ def test_main_openapi_msgspec_use_annotated_with_field_constraints():
                 / 'msgspec_use_annotated_with_field_constraints.py'
             ).read_text()
         )
+
+
+@freeze_time('2019-07-26')
+def test_main_openapi_discriminator_one_literal_as_default():
+    with TemporaryDirectory() as output_dir:
+        output_file: Path = Path(output_dir) / 'output.py'
+        return_code: Exit = main(
+            [
+                '--input',
+                str(OPEN_API_DATA_PATH / 'discriminator_enum.yaml'),
+                '--output',
+                str(output_file),
+                '--input-file-type',
+                'openapi',
+                '--output-model-type',
+                'pydantic_v2.BaseModel',
+                '--use-one-literal-as-default',
+            ]
+        )
+        assert return_code == Exit.OK
+        assert (
+            output_file.read_text()
+            == (
+                EXPECTED_OPENAPI_PATH
+                / 'discriminator'
+                / 'enum_one_literal_as_default.py'
+            ).read_text()
+        )