[BUG] [Spring] Generated @JsonSubTypes.Type value is incorrect for a model name with underscores

Description

Given a model with an underscore in the name, the generated

@JsonSubTypes.Type.value 

does not match the generated model class file name.

openapi-generator version

3.3.4

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Sample API
  description: API description in Markdown.
  version: 1.0.0
paths:
  /animals:
    get:
      summary: Returns all animals.
      description: Optional extended description in Markdown.
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Animal'
components:
  schemas:
    Dog_Animal:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    Cat_Animal:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    Animal:
      type: object
      discriminator:
        propertyName: className
      required:
        - className
      properties:
        className:
          type: string
        color:
          type: string
          default: red
               

(for YAML code) or

Command line used for generation

openapi-generator generate -g spring

Steps to reproduce

Invoke the command line above with the provided API definition.

Suggest a fix

Transform the name when adding the MappedModel to the discriminator in DefaultCodegen.createDiscriminator using DefaultCodegent.toModelName().

Start in DefaultCodegen.createDiscriminator and inspect how MappedModel names are added, then compare that with toModelName(). Run the supplied OpenAPI definition with the spring generator and inspect the generated @JsonSubTypes.Type.value and model class file names. Done means the discriminator value matches the generated model class name for underscored models.