[BUG] [JAVA] Java generation of 'extra' class with allOf

[renskesterrenburg]

Description

I am using the pet store example to create java classes with inheritance. In the newest release (4.0.1) I found a bug. When I generate code with the OpenApi declaration file it generates an extra class.

The class 'CatAllOf' I did not expect. It looks the same as 'Cat' except that it does not extends Pet.

OpenAPI declaration file:

openapi: 3.0.1
info:
  title: Article Event
  description: 'Article Event schema'
  version: 1.0.0
paths:
  /:
    get:
      responses:
        200:
          description: OK
          content: {}
components:
  schemas:
    TextChunk:
      type: object
      discriminator:
        propertyName: textChunkType
      properties:
        parent:
          type: string
    Dog:
      allOf: 
      - $ref: '#/components/schemas/TextChunk'
      - type: object
    Cat:
      allOf:
      - $ref: '#/components/schemas/TextChunk'
      - type: object
        properties:
          bark:
            type: string

openapi-generator version
I used the gradle plugin with version 4.0.1.

older version
I tested the same thing in the version 4.0.0-beta3 and there I did net see the 'extra' class. In other words, I got the expected behavior. It seems the bug was introduced with the latest release.

And it's not about presence of extra class only. The expected inheritance is missing as well.
It seems to me that the whole 4.x is affected

[gerardbosch]

I'm facing this issue as well. But when I have realized the version 4 of generator working this way I asked myself if this was intended or really a weird bug. Could someone clarify it? I was pretty happy with 3.3.4 so I will go back to it for now. I rely on Java inheritance.
@wing328

[yilinjuang]

Also happen in csharp client and server #3338

[wing328]

      - type: object
        properties:
          bark:
            type: string

That's treated as an inline schema (which can be replaced with $ref to avoid the additional model generation).

If users prefer the old way of not generating this inline schema, technically we can add an option to restore the old behaviour.

[valliman]

The proposed solutions would lead to a file being generated for the inline schema again. That sounds a bit counter-intuitive. Why would I want to give the inline schema a dedicated name, if I didn't had the need before?

[valliman]

@wing328 any comment on my post above? Is it possible to add the option to add the old behaviour?

[roxspring]

That's treated as an inline schema (which can be replaced with $ref to avoid the additional model generation).

This seems to miss the point entirely. Spec authors understand that these are inline schemas and are used precisely "to avoid the additional model generation". Replacing with a $ref necessitates the creation of the additional model that spec authors wish to avoid.

If users prefer the old way of not generating this inline schema, technically we can add an option to restore the old behaviour.

It seems clear from the number of bugs raised in this area that many users do "prefer the old way". What I'm really not clear on is:

1. What benefits there are to "the new way" - i.e. whether it's worth keeping both ways as options
2. Where in the codebase I should be looking to patch in order to address the underlying problem

[nexen505]

Still got this problem on 4.2.2.

[ahokkonen]

This is also a behavior for .net generators. Still an issue in 4.3.0

[papegaaij]

Even the examples have this issue. For example, the Java RestEasy example has several files with AllOf, like this one https://github.com/OpenAPITools/openapi-generator/blob/v4.3.0/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/CatAllOf.java

These files are not used at all by the API. The only reference to this class is an unused import from Cat and the testcase CatAllOfTest. The same is true for the other AllOf classes.

[wing328]

What about using .openapi-generator-ignore (in the output directory) to skip those files from being generated?