[BUG][kotlin-server][jaxrs-spec] Inheritance not supported

[pec0ra]

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

The new jaxrs-spec library of the kotlin-server generator does not support inheritance.

Inheritance can be represented in openapi with a discriminator and allOf. However, the kotlin-server generator gives an error when inheritance is used in an openapi spec:

Exception in thread "main" java.lang.RuntimeException: Could not generate model 'Pet'
	at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:532)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:888)
	at org.openapitools.codegen.cmd.Generate.execute(Generate.java:441)
	at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)
Caused by: org.openapitools.codegen.templating.TemplateNotFoundException: interface_req_var
	at org.openapitools.codegen.templating.MustacheEngineAdapter.findTemplate(MustacheEngineAdapter.java:79)
	at org.openapitools.codegen.templating.MustacheEngineAdapter.lambda$compileTemplate$0(MustacheEngineAdapter.java:61)
	at com.samskivert.mustache.Mustache$IncludedTemplateSegment.execute(Mustache.java:756)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:870)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:866)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:881)
	at com.samskivert.mustache.Template.executeSegs(Template.java:157)
	at com.samskivert.mustache.Mustache$IncludedTemplateSegment.execute(Mustache.java:774)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$InvertedSegment.execute(Mustache.java:910)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$InvertedSegment.execute(Mustache.java:906)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$InvertedSegment.execute(Mustache.java:910)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:881)
	at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
	at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:866)
	at com.samskivert.mustache.Template.executeSegs(Template.java:157)
	at com.samskivert.mustache.Template.execute(Template.java:134)
	at com.samskivert.mustache.Template.execute(Template.java:125)
	at org.openapitools.codegen.templating.MustacheEngineAdapter.compileTemplate(MustacheEngineAdapter.java:65)
	at org.openapitools.codegen.TemplateManager.write(TemplateManager.java:163)
	at org.openapitools.codegen.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:1034)
	at org.openapitools.codegen.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:1021)
	at org.openapitools.codegen.DefaultGenerator.generateModel(DefaultGenerator.java:388)
	at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:523)
	... 4 more

openapi-generator version

Tested with openapi-generator version 5.4.0 and the docker image openapitools/openapi-generator-cli:latest (as of Feb 9th 2022).

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  description: |
    kotlin-server jaxrs-spec inheritance issues
  title: inheritance bug
  version: 1.0.0
paths:
  /test:
    get:
      responses:
        '200':
          description: ok
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Pet'
servers:
  - url: http://localhost/
components:
  schemas:
    Pet:
      type: object
      required:
        - pet_type
      properties:
        pet_type:
          type: string
      discriminator:
        propertyName: pet_type
        mapping:
          cachorro: Dog
    Cat:
      allOf:
        - $ref: '#/components/schemas/Pet'
        - type: object
          # all other properties specific to a `Cat`
          properties:
            name:
              type: string
    Dog:
      allOf:
        - $ref: '#/components/schemas/Pet'
        - type: object
          # all other properties specific to a `Dog`
          properties:
            bark:
              type: string
    Lizard:
      allOf:
        - $ref: '#/components/schemas/Pet'
        - type: object
          # all other properties specific to a `Lizard`
          properties:
            lovesRocks:
              type: boolean

Generation Details

Generator: kotlin-server
Library: jaxrs-spec

Was tested with the following command:

docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli generate -i /local/petstore.yaml -g kotlin-server -o /local/out/kotlin --library jaxrs-spec

where the spec given above is present in the current directory as petstore.yaml

Steps to reproduce

docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli generate -i /local/petstore.yaml -g kotlin-server -o /local/out/kotlin --library jaxrs-spec

where the spec given above is present in the current directory as petstore.yaml

Related issues/PRs

The new kotlin-server jaxrs-spec was introduced in #10830

The missing interface_req_var template is not the only problem with inheritance for this generator. The interface_opt_var is also missing.

In addition, there also seem to be an issue with the generated code when using multiple levels of inheritance.

Suggest a fix

A good start would be using the templates from the kotlin-client generator:
https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/kotlin-client/interface_opt_var.mustache
https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/kotlin-client/interface_req_var.mustache

Other changes will be needed though, like marking the parent's fields as override in the children classes.

[pedro-borges]

I am also trying to generate kotlin jaxrs models with no success, has this been accepted as a bug? or is there a workaround?

[pec0ra]

I am also trying to generate kotlin jaxrs models with no success, has this been accepted as a bug? or is there a workaround?

As a quick workaround, you can add the two mustache templates mentioned above in your open api template directory (See https://openapi-generator.tech/docs/templating/#modifying-templates). This won't really fix inheritance but at least you will be able to generate the code without error.