[BUG] [Python] to_json function raise error on date type

[imyixiao]

Bug Report Checklist

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

Description

[BUG] [Python] to_json function raise error on date type: TypeError: Object of type date is not JSON serializable

openapi-generator version

7.4

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: API
  description: API
  version: 1.4.0
paths:
  /create:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Pet"
      responses:
        "202":
          description: OK
components:
  schemas:
    Pet:
      type: object
      properties:
        asOfDate:
          format: date
          type: string
        color:
          type: string

Generation Details

Steps to reproduce

1. generate sdk with the spec and version 7.4
2. use the code below to test it

pet_dict = {
        "color": "blue",
        "asOfDate": "2020-03-03"
    }
    pet = SDK.Pet.from_json(json.dumps(pet_dict))
    print(pet)
    // error: Object of type date is 
not JSON serializable
    pet.to_json()

Related issues/PRs

Suggest a fix

[alfechner]

I have the exact same issue.

This is my work around for now:

json.dumps(pipeline.to_dict(), default=str)

[imyixiao]

my workaround is editing the model_generic.mustache

    def to_json(self) -> str:
        _dict_res = self.to_dict()
        for k, v in _dict_res.items():
            if isinstance(v, (generic_datetime.date, generic_datetime.datetime)):
                _dict_res[k] = v.isoformat()
        return json.dumps(_dict_res)

[bgunebakan]

I created custom model_generic.mustache with new to_json() method. It works with excluded fields also.

def to_json(self) -> str:
        """Returns the JSON representation of the model using alias"""
        excluded_fields: Set[str] = set([
            {{#vendorExtensions.x-py-readonly}}
            "{{{.}}}",
            {{/vendorExtensions.x-py-readonly}}
            {{#isAdditionalPropertiesTrue}}
            "additional_properties",
            {{/isAdditionalPropertiesTrue}}
        ])
        return self.model_dump_json(by_alias=True, exclude_unset=True, exclude=excluded_fields)

[wing328]

Do you mind submitting a PR with the suggested change?

[bilaltonga]

Do you mind submitting a PR with the suggested change?

Actually I'm preparing a PR with this change.