[BUG] [PYTHON] Model property: required AND default NOT combinable

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

I want to have a required property with a default value. When I require it in the model spec, it loses the default= parameter in the Field() constructor. I need it to be required since, if it isn't, it could be None.

Firstly, is this intended? If so how am I supposed to set up the property? If not, please help :)

openapi-generator version

master/7.5.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Title
  description: Title
  version: 1.0.0
paths:
  '/user':
    get:
      responses:
        200:
          description: "success"
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/RequiredProperties'

components:
  schemas:
    RequiredProperties:
      type: object
      required:
        - requiredWithDefault
        - requiredWithoutDefault
      properties:
        requiredWithoutDefault:
          type: string
        requiredWithDefault:
          type: string
          default: "4.5.0"
        notRequiredWithDefault:
          type: string
          default: "4.5.0"
        notRequiredWithoutDefault:
          type: string

Generation Details

java -jar openapi-generator-cli.jar generate -i required.yaml -g python -o object --additional-properties packageName=object_client

Steps to reproduce

1. Generate from provided spec
2. See Model class

class RequiredProperties(BaseModel):
    """
    RequiredProperties
    """ # noqa: E501
    required_with_default: StrictStr = Field(alias="requiredWithDefault")
    required_without_default: StrictStr = Field(alias="requiredWithoutDefault")
    not_required_with_default: Optional[StrictStr] = Field(default='4.5.0', alias="notRequiredWithDefault")
    not_required_without_default: Optional[StrictStr] = Field(default=None, alias="notRequiredWithoutDefault")
    __properties: ClassVar[List[str]] = ["requiredWithDefault", "requiredWithoutDefault", "notRequiredWithDefault", "notRequiredWithoutDefault"]

Interestingly enough, the default shows up in the from_dict() classmethod:

        _obj = cls.model_validate({
            "requiredWithDefault": obj.get("requiredWithDefault") if obj.get("requiredWithDefault") is not None else '4.5.0',
            "requiredWithoutDefault": obj.get("requiredWithoutDefault"),
            "notRequiredWithDefault": obj.get("notRequiredWithDefault") if obj.get("notRequiredWithDefault") is not None else '4.5.0',
            "notRequiredWithoutDefault": obj.get("notRequiredWithoutDefault")
        })

Suggest a fix

I haven't quite found the problem yet, I'm pretty sure this is the part that's causing it: https://github.com/OpenAPITools/openapi-generator/blob/a4cf255dce69b74fabe49161d75bdc39851d1d95/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java#L914

Start at AbstractPythonPydanticV1Codegen.java around line 914, which the report identifies as related to the missing default. Generate the supplied OpenAPI YAML with the Python generator and inspect the RequiredProperties model and from_dict() output. Done means a required property with a default retains the default in its Field() declaration without changing the other generated properties.