Array where items are nullable strings fails validation with `OpenapiFirst::ResponseInvalidError`

[nfm]

I have an API response where the property value is an array of strings, with null values allowed:

# Example API response:
{ "path": ["1", "2", null] }

With this partial schema, I'm seeing the above API response fail validation:

path:
  type: array
  items:
    type: string
    # The last item can be null to signify the participant 'passed'
    nullable: true

With this error:

OpenapiFirst::ResponseInvalidError in MyController#some_action

Response body is invalid: value at `/path/2` is not a string.

I also tried this:

path:
  type: array
  items:
    oneOf:
      - type: string
    nullable: true

Hopefully that makes sense, please let me know if a reproduction repro would be helpful of if this is enough context 🙏 Thanks!

[nfm]

I forgot to mention - we're on OAS 3.0.3. I think there's some changes to nullable in the spec for 3.1, so there might be some overlap with this issue and our schema version.

[ahx]

I forgot to mention - we're on OAS 3.0.3. I think there's some changes to nullable in the spec for 3.1, so there might be some overlap with this issue and our schema version.

Yes. nullable was removed in 3.1. This library should pass the used OAS version to json_schemer which then takes care of the validation. So it should handle nullable according to the used version. If that does not work it looks like openapi_first passes the wrong version to json_schemer.

Are you sure your OAD is on 3.0? I will have a look at this shortly. A failing test would speed things up.

Thanks for the report!

[ahx]

Your second example should not work, though, because oneOf does not consider schema keywords on the same level as nullable oneOf

[nfm]

Thanks @ahx ❤️ I'll put together a minimal reproduction in the next few days.

Can confirm we're on 3.0.3 currently.

[ahx]

Hey @nfm, in case you are trying to add a (failing) test about this: I repeatedly ask myself where to put these kinds of tests. Usually I end up adding them to the tests for response validation middleware, but I don’t think that is an obvious place to put them. So I think we need a better place for those. If you have any thoughts about that, please share. A repository with a minimal example would be helpful as well, though. So don’t feel obliged to look into the unit test setup if you cannot do that right now. Thanks.

[ahx]

Hi @nfm I was not able to reproduce this issue. I have added an example to reproduce this issue, but so far the validation behaves as expected.

I will close this now, but please re-open it if the problem could not be solved on your side somehow.