Support "nullable" (OpenApi 3.0 only)

[ahx]

Currently OpenapiFirst does not support "nullable" of the OpenApi flavoured JSON Schema.

See davishmcclurg/json_schemer#22

[ahx]

json_schemer is currently not a good place to impement something like that.
Here's an idea for a new rubygem:

require 'openapi-json-schema-converter'
OpenapiJsonSchemaConverter.new(openapi_json_schema).call(data) # => standard_json_schema

[tristandruyen]

@ahx
FYI this is a workaround we found:

some_thing:
  oneOf:
    - type: 'null'   # Note the quotes around 'null'
    - type: string

which could be improved once OpenAPI 3.1 (#46) is supported to:

some_thing:
  type: ['null',string]

so does this even need to stay open?

[ahx]

type: ['null',string] should work, even though it is not officially supported by OAS 3.0.

I think supporting nullable would be useful, because we could use standard OAS linters that would fail when using type: ['null',string]. OAS 3.1 solves all this, but unfortunately it has not reached RC status, yet.

[ahx]

This should be obsolete with OAS 3.1, since nullable will be removed from OpenAPI 3.1 and type arrays will be valid type: ['null', string ] 👍.
I think we can close this.

[ahx]

Reopening, because I want to support OpenAPI 3.0.x

[ahx]

Reopening, because current implementation does not work with allOf, oneOf :|

[ahx]

@JF-Lalonde nullable has been removed from OAS since 3.1. Is updating your spec to 3.1 an option for you/your team?

[JF-Lalonde]

@ahx Good to know! We've actually adopted the type: ['null',string] already even though it's not officially supported. But we'll probably be upgrading to 3.1 soon.

[ahx]

FYI this will be solved in 1.0, because json_schemer supports it with it's OpenAPI 3.0 / 3.1 metaschema