[BUG] [JAVA] openapi-generator-maven-plugin does not handle allOf composed of multiple objects

Bug Report Checklist

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

Description

Using allOf composed of multiple objects in a response does not generate a class combining these multiple objects. Instead it uses the first class defined in the allOf section.

openapi-generator version

Version 5.2.0:

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>5.2.0</version>
</plugin>

I have also tested with master (5.2.1-SNAPSHOT), commit fe9636e9.

OpenAPI declaration file content or url

Important part here is the allOf:

openapi: 3.0.0
info:
  title: Test
  version: v1
paths:
  /test:
    get:
      operationId: get
      responses:
        '200':
          description: Get
          content:
            application/json:
              schema:
                allOf:
                  - $ref: '#/components/schemas/A'
                  - $ref: '#/components/schemas/B'
components:
  schemas:
    A:
      type: object
      properties:
        attA:
          type: string
    B:
      type: object
      properties:
        attB:
          type: integer

Generation Details

generatorName: java
inputSpec: openapi.yaml

Steps to reproduce

 mvn org.openapitools:openapi-generator-maven-plugin:5.2.0:generate \
    -Dopenapi.generator.maven.plugin.inputSpec=openapi.yaml \
    -Dopenapi.generator.maven.plugin.generatorName=java

Shows a warning:

[WARNING] allOf with multiple schemas defined. Using only the first one: A

It generates classes A and B. But when calling get(), the value returned by the call is A:

DefaultApi api = new DefaultApi();
A a = api.get();

I expected instead a composite object with A and B properties (attA and attB), like this (result from https://editor.swagger.io/):

Related issues/PRs

Suggest a fix

[nicobo]

I guess this is the cause for other issues :

• https://github.com/OpenAPITools/openapi-generator/issues/10024
• https://github.com/OpenAPITools/openapi-generator/issues/10010
• https://github.com/OpenAPITools/openapi-generator/issues/6796

And I have the same issue with html2 generators also…

[norbjd]

@paulbors of course editing the spec is possible (and that’s the solution we used now), but this is not very convenient if the openapi evolves : we have to manually change our version to match the new version.

Besides, as you said editing the openapi is just a workaround.

That’s why I opened this issue : the fact that the generator does not generate right classes when providing a valid openapi spec (as in my example) is probably a bug and as so probably needs to be fixed.