Discriminator does not work for polymorphic types with oneOf

[zdenecek]

Describe the bug
Discriminator does not work for polymorphic types

To Reproduce

Example schema:

openapi: 3.1.0
info:
  title: Test
  description: "Test API"
  version: 0.0.0
paths:
  /pet:
    get:
      responses:
        '200':
          description: "Pet"
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/PetContainer"
components:
  schemas:
    PetContainer:
      type: object
      required:
        - pet
      properties:
        pet:
          $ref: "#/components/schemas/Pet"
    Pet:
      type: object
      required:
        - petType
      properties:
        petType:
          type: string
      oneOf:
        - $ref: "#/components/schemas/Cat"
        - $ref: "#/components/schemas/Dog"
        - $ref: "#/components/schemas/Lizard"
      discriminator:
        propertyName: petType
        mapping:
          cat: "#/components/schemas/Cat"
          dog: "#/components/schemas/Dog"
          lizard: "#/components/schemas/Lizard"
    Cat:
      type: object
      # all other properties specific to a `Cat`
      properties:
        name:
          type: string
    Dog:
      type: object
      # all other properties specific to a `Dog`
      properties:
        bark:
          type: string
    Lizard:
      type: object
      # all other properties specific to a `Lizard`
      properties:
        lovesRocks:
          type: boolean

Used commandline:

$ datamodel-codegen --input openapi.yaml --input-file-type openapi  --output-model-type pydantic_v2.BaseModel --output schemas.py  --snake-case-field  --use-annotated --use-union-operator --target-python-version '3.11'

Expected behavior

from schemas import PetContainer, Cat
import json 

json_data = """
    {
        "pet": {
            "name": "Meow-Meow",
            "petType": "cat"
        }   
    }
    """

container = PetContainer.model_validate_json(json_data)

try:
    cat_name = container.pet.name
except AttributeError:
    cat_name = None
    
    
assert isinstance(container.pet, Cat)
assert cat_name == "Meow-Meow"

Version:

• OS: macOS
• Python version: 3.11
• datamodel-code-generator version: 35

Additional context
See https://github.com/zdenecek/openapi-discriminator-allof-demo