Nullable required fields should not have default value (#2520)

Co-authored-by: Antonio Spadaro <ilovelinux@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Bernát Gábor <gaborjbernat@gmail.com>
Co-authored-by: Bernát Gábor <bgabor8@bloomberg.net>

Author: 4 people

docs/cli-reference/model-customization.md

@@ -3151,7 +3151,7 @@ for the generated code. Supported values include `pydantic.BaseModel`,
             
             
             class MyObjItem(BaseModel):
-                items: list[Any] | None = None
+                items: list[Any] | None
             
             
             class Model(BaseModel):

src/datamodel_code_generator/model/template/pydantic_v2/BaseModel.jinja2

@@ -32,7 +32,7 @@ class {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comme
     {%- else %}
     {{ field.name }}: {{ field.type_hint }}
     {%- endif %}
-    {%- if not field.has_default_factory_in_field and (not (field.required or (field.represented_default == 'None' and field.strip_default_none)) or field.data_type.is_optional)
+    {%- if not field.has_default_factory_in_field and not field.required and (field.represented_default != 'None' or not field.strip_default_none or field.data_type.is_optional)
             %} = {{ field.represented_default }}
     {%- endif -%}
     {%- endif %}

tests/data/expected/main/jsonschema/null_and_array_v2.py

@@ -10,7 +10,7 @@
 
 
 class MyObjItem(BaseModel):
-    items: list[Any] | None = None
+    items: list[Any] | None
 
 
 class Model(BaseModel):

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

@@ -0,0 +1,14 @@
+# generated by datamodel-codegen:
+#   filename:  nullable_required_annotated.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Annotated
+
+from pydantic import BaseModel, Field
+
+
+class Person(BaseModel):
+    first_name: Annotated[str | None, Field(alias='firstName')]
+    last_name: Annotated[str | None, Field(alias='lastName')]

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

@@ -8,7 +8,7 @@
 
 
 class Thing(BaseModel):
-    value: str | None = None
+    value: str | None
 
 
 class NullThing(RootModel[None]):

tests/data/openapi/nullable_required_annotated.yaml

@@ -0,0 +1,20 @@
+openapi: 3.0.3
+info:
+  version: 1.0.0
+  title: Nullable Required Test
+  description: Test case for nullable + required fields with Annotated
+paths: {}
+components:
+  schemas:
+    Person:
+      type: object
+      properties:
+        firstName:
+          type: string
+          nullable: true
+        lastName:
+          type: string
+          nullable: true
+      required:
+        - firstName
+        - lastName

tests/main/openapi/test_main_openapi.py

@@ -2691,6 +2691,24 @@ def test_main_openapi_nullable_31(output_file: Path) -> None:
     )
 
 
+def test_main_openapi_nullable_required_annotated(output_file: Path) -> None:
+    """Test OpenAPI generation with nullable required fields using annotations."""
+    run_main_and_assert(
+        input_path=OPEN_API_DATA_PATH / "nullable_required_annotated.yaml",
+        output_path=output_file,
+        input_file_type="openapi",
+        assert_func=assert_file_content,
+        expected_file="nullable_required_annotated.py",
+        extra_args=[
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+            "--strict-nullable",
+            "--use-annotated",
+            "--snake-case-field",
+        ],
+    )
+
+
 @pytest.mark.cli_doc(
     options=["--custom-file-header-path"],
     input_schema="openapi/api.yaml",