Strip Field None defaults with metadata

src/datamodel_code_generator/model/pydantic_base.py

@@ -235,6 +235,12 @@ def _process_data_in_str(self, data: dict[str, Any]) -> None:  # pragma: no cove
     def _process_annotated_field_arguments(self, field_arguments: list[str]) -> list[str]:  # noqa: PLR6301
         return field_arguments
 
+    def _should_strip_default_none_from_field(self) -> bool:
+        if self.data_type.is_optional:
+            return False
+
+        return self.default is None
+
     def _get_field_data_and_default_factory(self) -> tuple[dict[str, Any], Any]:
         """Build Field() keyword data and the effective default_factory."""
         data: dict[str, Any] = {k: v for k, v in self.extras.items() if k not in self._EXCLUDE_FIELD_KEYS}
@@ -306,8 +312,11 @@ def __str__(self) -> str:
             and not self.extras.get("validate_default")
         ):
             field_arguments = ["...", *field_arguments]
-        elif not default_factory:
-            default_repr = represent_python_value(self.default)
+        elif (
+            not default_factory
+            and (default_repr := represent_python_value(self.default))
+            and (not self.strip_default_none or not self._should_strip_default_none_from_field())
+        ):
             field_arguments = [default_repr, *field_arguments]
 
         if self.is_class_var:

tests/data/expected/main/jsonschema/root_in_enum.py

@@ -14,11 +14,8 @@ class Model(BaseModel):
         populate_by_name=True,
     )
     order_reference: str | None = Field(
-        None,
         alias='orderReference',
         description='Reference number of the order',
         examples=['27378669'],
     )
-    brand: Literal['OPUS', 'someday'] | None = Field(
-        None, description='purchased brand'
-    )
+    brand: Literal['OPUS', 'someday'] | None = Field(description='purchased brand')

tests/data/expected/main/openapi/pyproject.py

@@ -55,22 +55,18 @@ class Error(BaseModel):
 
 class Api(BaseModel):
     api_key: str | None = Field(
-        None,
         alias="apiKey",
         description="To be used as a dataset parameter value",
     )
     api_version_number: str | None = Field(
-        None,
         alias="apiVersionNumber",
         description="To be used as a version parameter value",
     )
     api_url: AnyUrl | None = Field(
-        None,
         alias="apiUrl",
         description="The URL describing the dataset's fields",
     )
     api_documentation_url: AnyUrl | None = Field(
-        None,
         alias="apiDocumentationUrl",
         description="A URL to the API console for each API",
     )

tests/data/expected/main/openapi/strip_default_none_pydantic_v2.py

@@ -0,0 +1,21 @@
+# generated by datamodel-codegen:
+#   filename:  strip_default_none_pydantic_v2.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+
+class Issue1816Model(BaseModel):
+    metadataOnly: str | None = Field(description='Optional field with metadata only.')
+    nullableMetadata: str | None = Field(
+        None, description='Nullable field with metadata.'
+    )
+    explicitDefault: str | None = Field(
+        'active', description='Optional field with a non-None default.'
+    )
+    stringNoneDefault: str | None = Field(
+        'None', description='Optional field with a string None default.'
+    )
+    plainOptional: str | None

tests/data/expected/main/openapi/with_strip_default_none.py

@@ -41,17 +41,13 @@ class Error(BaseModel):
 
 
 class Api(BaseModel):
-    apiKey: str | None = Field(
-        None, description='To be used as a dataset parameter value'
-    )
+    apiKey: str | None = Field(description='To be used as a dataset parameter value')
     apiVersionNumber: str | None = Field(
-        None, description='To be used as a version parameter value'
-    )
-    apiUrl: AnyUrl | None = Field(
-        None, description="The URL describing the dataset's fields"
+        description='To be used as a version parameter value'
     )
+    apiUrl: AnyUrl | None = Field(description="The URL describing the dataset's fields")
     apiDocumentationUrl: AnyUrl | None = Field(
-        None, description='A URL to the API console for each API'
+        description='A URL to the API console for each API'
     )
 
 

tests/data/openapi/strip_default_none_pydantic_v2.yaml

@@ -0,0 +1,28 @@
+openapi: 3.0.3
+info:
+  title: strip default none regression
+  version: 1.0.0
+paths: {}
+components:
+  schemas:
+    Issue1816Model:
+      type: object
+      properties:
+        metadataOnly:
+          type: string
+          description: Optional field with metadata only.
+        nullableMetadata:
+          anyOf:
+            - type: string
+            - type: "null"
+          description: Nullable field with metadata.
+        explicitDefault:
+          type: string
+          description: Optional field with a non-None default.
+          default: active
+        stringNoneDefault:
+          type: string
+          description: Optional field with a string None default.
+          default: "None"
+        plainOptional:
+          type: string

tests/main/openapi/test_main_openapi.py

@@ -1307,6 +1307,18 @@ def test_main_with_strip_default_none(output_file: Path) -> None:
     )
 
 
+def test_main_openapi_pydantic_v2_strip_default_none_field_metadata(output_file: Path) -> None:
+    """Test strip-default-none removes implicit None defaults from Field metadata."""
+    run_main_and_assert(
+        input_path=OPEN_API_DATA_PATH / "strip_default_none_pydantic_v2.yaml",
+        output_path=output_file,
+        input_file_type="openapi",
+        assert_func=assert_file_content,
+        expected_file="strip_default_none_pydantic_v2.py",
+        extra_args=["--strip-default-none", "--output-model-type", "pydantic_v2.BaseModel"],
+    )
+
+
 def test_disable_timestamp(output_file: Path) -> None:
     """Test OpenAPI generation with timestamp disabled."""
     run_main_and_assert(