Fix default for annotated field in pydantic v2 (#1498)

* Fix default for annotated field in pydantic v2

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Move v2 logic to v2 model

---------

Co-authored-by: ferris <ferris@devdroplets.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Koudai Aono <koxudaxi@gmail.com>

datamodel_code_generator/model/pydantic/base_model.py

@@ -125,6 +125,11 @@ def _process_data_in_str(self, data: Dict[str, Any]) -> None:
         if self.const:
             data['const'] = True
 
+    def _process_annotated_field_arguments(
+        self, field_arguments: List[str]
+    ) -> List[str]:
+        return field_arguments
+
     def __str__(self) -> str:
         data: Dict[str, Any] = {
             k: v for k, v in self.extras.items() if k not in self._EXCLUDE_FIELD_KEYS
@@ -180,7 +185,7 @@ def __str__(self) -> str:
             return ''
 
         if self.use_annotated:
-            pass
+            field_arguments = self._process_annotated_field_arguments(field_arguments)
         elif self.required:
             field_arguments = ['...', *field_arguments]
         elif default_factory:

datamodel_code_generator/model/pydantic_v2/base_model.py

@@ -100,6 +100,20 @@ def _process_data_in_str(self, data: Dict[str, Any]) -> None:
         # unique_items is not supported in pydantic 2.0
         data.pop('unique_items', None)
 
+    def _process_annotated_field_arguments(
+        self, field_arguments: List[str]
+    ) -> List[str]:
+        if not self.required:
+            if self.use_default_kwarg:
+                return [
+                    f'default={repr(self.default)}',
+                    *field_arguments,
+                ]
+            else:
+                # TODO: Allow '=' style default for v1?
+                return [f'{repr(self.default)}', *field_arguments]
+        return field_arguments
+
 
 class ConfigAttribute(NamedTuple):
     from_: str

datamodel_code_generator/model/template/pydantic_v2/BaseModel.jinja2

@@ -24,7 +24,7 @@ class {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comme
     {%- else %}
     {{ field.name }}: {{ field.type_hint }}
     {%- endif %}
-    {%- if not field.required or field.data_type.is_optional or field.nullable
+    {%- if (not field.required or field.data_type.is_optional or field.nullable) and not field.annotated
             %} = {{ field.represented_default }}
     {%- endif -%}
     {%- endif %}

tests/data/expected/main/main_use_annotated_with_field_constraints_pydantic_v2/output.py

@@ -0,0 +1,92 @@
+# generated by datamodel-codegen:
+#   filename:  api_constrained.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Annotated, List, Optional, Union
+
+from pydantic import AnyUrl, BaseModel, Field, RootModel
+
+
+class Pet(BaseModel):
+    id: Annotated[int, Field(ge=0, le=9223372036854775807)]
+    name: Annotated[str, Field(max_length=256)]
+    tag: Annotated[Optional[str], Field(None, max_length=64)]
+
+
+class Pets(RootModel[List[Pet]]):
+    root: Annotated[List[Pet], Field(max_length=10, min_length=1)]
+
+
+class UID(RootModel[int]):
+    root: Annotated[int, Field(ge=0)]
+
+
+class Phone(RootModel[str]):
+    root: Annotated[str, Field(min_length=3)]
+
+
+class FaxItem(RootModel[str]):
+    root: Annotated[str, Field(min_length=3)]
+
+
+class User(BaseModel):
+    id: Annotated[int, Field(ge=0)]
+    name: Annotated[str, Field(max_length=256)]
+    tag: Annotated[Optional[str], Field(None, max_length=64)]
+    uid: UID
+    phones: Annotated[Optional[List[Phone]], Field(None, max_length=10)]
+    fax: Optional[List[FaxItem]] = None
+    height: Annotated[Optional[Union[int, float]], Field(None, ge=1.0, le=300.0)]
+    weight: Annotated[Optional[Union[float, int]], Field(None, ge=1.0, le=1000.0)]
+    age: Annotated[Optional[int], Field(None, gt=0, le=200)]
+    rating: Annotated[Optional[float], Field(None, gt=0.0, le=5.0)]
+
+
+class Users(RootModel[List[User]]):
+    root: List[User]
+
+
+class Id(RootModel[str]):
+    root: str
+
+
+class Rules(RootModel[List[str]]):
+    root: List[str]
+
+
+class Error(BaseModel):
+    code: int
+    message: str
+
+
+class Api(BaseModel):
+    apiKey: Annotated[
+        Optional[str],
+        Field(None, description='To be used as a dataset parameter value'),
+    ]
+    apiVersionNumber: Annotated[
+        Optional[str],
+        Field(None, description='To be used as a version parameter value'),
+    ]
+    apiUrl: Annotated[
+        Optional[AnyUrl],
+        Field(None, description="The URL describing the dataset's fields"),
+    ]
+    apiDocumentationUrl: Annotated[
+        Optional[AnyUrl],
+        Field(None, description='A URL to the API console for each API'),
+    ]
+
+
+class Apis(RootModel[List[Api]]):
+    root: List[Api]
+
+
+class Event(BaseModel):
+    name: Optional[str] = None
+
+
+class Result(BaseModel):
+    event: Optional[Event] = None

tests/test_main.py

@@ -4251,7 +4251,17 @@ def test_jsonschema_without_titles_use_title_as_name():
 
 
 @freeze_time('2019-07-26')
-def test_main_use_annotated_with_field_constraints():
+@pytest.mark.parametrize(
+    'output_model,expected_output',
+    [
+        ('pydantic.BaseModel', 'main_use_annotated_with_field_constraints'),
+        (
+            'pydantic_v2.BaseModel',
+            'main_use_annotated_with_field_constraints_pydantic_v2',
+        ),
+    ],
+)
+def test_main_use_annotated_with_field_constraints(output_model, expected_output):
     with TemporaryDirectory() as output_dir:
         output_file: Path = Path(output_dir) / 'output.py'
         return_code: Exit = main(
@@ -4264,16 +4274,14 @@ def test_main_use_annotated_with_field_constraints():
                 '--use-annotated',
                 '--target-python-version',
                 '3.9',
+                '--output-model',
+                output_model,
             ]
         )
         assert return_code == Exit.OK
         assert (
             output_file.read_text()
-            == (
-                EXPECTED_MAIN_PATH
-                / 'main_use_annotated_with_field_constraints'
-                / 'output.py'
-            ).read_text()
+            == (EXPECTED_MAIN_PATH / expected_output / 'output.py').read_text()
         )