[BUG] [Python] Model generated without any properties

[Mapiarz]

Description

The generator seems to generate a pydantic model without any properties, thus is useless. See below for full example.

openapi-generator version

7.0.1

OpenAPI declaration file content or url

This is minimal schema that reproduces the issue. This schema comes from third party and is outside of my control, I cannot change it.

openapi: 3.0.0

info:
  title: Foo
  version: 1.0.0

paths:
  /foo:
    get:
      responses:
        '200':
          description: example
          content:
            application/json:
              schema:
                type: array
                items:
                 $ref: '#/components/schemas/Payment'


components:
  schemas:
    DateTime:
      type: string
      format: date-time
      example: "2019-01-01T00:00:00"
    Datetime:
      allOf:
        - $ref: '#/components/schemas/DateTime'
      example: "2019-01-01 00:00:00" 
    Payment:
      type: object
      properties:
        date:
          $ref: '#/components/schemas/Datetime'
        amount:
          type: number
          format: float
          example: 625.0

Generation Details

Generating the sdk like this:
pnpm dlx @openapitools/openapi-generator-cli generate -i spec.yaml -g python -o /package --package-name my_package

It generates a Datetime pydantic model without any properties:

# coding: utf-8

"""
    Foo

    No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)

    The version of the OpenAPI document: 1.0.0
    Generated by OpenAPI Generator (https://openapi-generator.tech)

    Do not edit the class manually.
"""  # noqa: E501


from __future__ import annotations
import pprint
import re  # noqa: F401
import json



from pydantic import BaseModel

class Datetime(BaseModel):
    """
    Datetime
    """
    __properties = []

    class Config:
        """Pydantic configuration"""
        allow_population_by_field_name = True
        validate_assignment = True

    def to_str(self) -> str:
        """Returns the string representation of the model using alias"""
        return pprint.pformat(self.dict(by_alias=True))

    def to_json(self) -> str:
        """Returns the JSON representation of the model using alias"""
        return json.dumps(self.to_dict())

    @classmethod
    def from_json(cls, json_str: str) -> Datetime:
        """Create an instance of Datetime from a JSON string"""
        return cls.from_dict(json.loads(json_str))

    def to_dict(self):
        """Returns the dictionary representation of the model using alias"""
        _dict = self.dict(by_alias=True,
                          exclude={
                          },
                          exclude_none=True)
        return _dict

    @classmethod
    def from_dict(cls, obj: dict) -> Datetime:
        """Create an instance of Datetime from a dict"""
        if obj is None:
            return None

        if not isinstance(obj, dict):
            return Datetime.parse_obj(obj)

        _obj = Datetime.parse_obj({
        })
        return _obj

[fa0311]

Duplicate Datetime key.
Please use the correct yaml format.

[Mapiarz]

It's DateTime and Datetime. Are you saying it's case insensitive?

[fa0311]

I was mistaken. It is case sensitive.
More research is needed.

[wing328]

update: I've filed #16943 to fix it