[BUG] nullable schema is not allowed to contain null

[domenkozar]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used? 5.0.0
• Have you search for related issues/PRs?
• What's the actual output vs expected output?

Description

Generator crashes if nullable enum schema contains null value.

This is allowed by jsonschema and thus openapi spec.

openapi-generator version

5.0.0 branch, 4th Feb 2020

OpenAPI declaration file content or url

rating:
      type: string
      nullable: true
      enum:
        - null 
        - Gibberish

Command line used for generation

openapi-generator-cli  generate --input-spec openapi.yaml --enable-post-process-file --generator-name elm --config openapi-generator.yml  --output openapi-client

Steps to reproduce

There's an error:

Exception in thread "main" java.lang.RuntimeException: Could not process model 'rating'.Please make sure that your schema is correct!
        at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:473)
        at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:938)
        at org.openapitools.codegen.cmd.Generate.run(Generate.java:423)
        at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:61)
Caused by: java.lang.NullPointerException
        at org.openapitools.codegen.DefaultCodegen.postProcessModelsEnum(DefaultCodegen.java:490)
        at org.openapitools.codegen.languages.ElmClientCodegen.postProcessModels(ElmClientCodegen.java:321)
        at org.openapitools.codegen.DefaultGenerator.processModels(DefaultGenerator.java:1214)
        at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:468)
        ... 3 more

[domenkozar]

cc @eriktim

[eriktim]

Thanks for opening this issue @domenkozar.
The error seems to be misleading. I think the issue is you're using null as an enum value here which seems to be unsupported. I'm not sure what you're trying to achieve here, but I think there are two options for now:

1. You want null to be one of the values of the enum. In that case you should write "null" in the yaml instead, or

2. You want the enum to be nullable. In that case I would recommend providing the non-nullable enum as a type and whereever you use it you can use nullable/[not-]required. For example:

optionA:
  required:
    - rating
  properties:
    rating:
      $ref: '#/components/schemas/rating'
      nullable: true
optionB:
  properties:
    rating:
      $ref: '#/components/schemas/rating'
rating:
      type: string
      enum:
        - Gibberish

@wing328 can you clarify what the desired behavior is here?

[domenkozar]

OpenAPI specification says schemas respect jsonschema, which does allow for my example.

See OAI/OpenAPI-Specification#1900 (comment)

[eriktim]

Yes I've seen that one but it seems the OpenAPI generator does not support this (yet?). It's not the Elm generator breaking here.

[domenkozar]

Thanks - I've updated issue title to reflect that.

[zupo]

Hey @eriktim, where should I report this so that it gets fixed in the "OpenAPI generator", so that I can then help getting it fixed for Elm?

[eriktim]

@zupo this should be the right location. I was actually hoping for @wing328 to give some clarity on this issue.