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?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

In Ruby client, it's not possible to set NULL on any value (I suppose it should be "nullable": true in yaml definition)

openapi-generator version

3.3.4, 4.0.0, 4.1.1, 4.2.0

OpenAPI declaration file content or url

https://github.com/ManageIQ/topological_inventory-ingress_api/blob/12b92fbdb9485d01b7840318dc42a384f557286a/public/doc/openapi-3-v0.0.2.json#L4243
https://github.com/ManageIQ/topological_inventory-ingress_api/blob/12b92fbdb9485d01b7840318dc42a384f557286a/public/doc/openapi-3-v0.0.2.json#L4252
(2nd case: Is it possible to set nullable to ref?)

Command line used for generation

java -jar openapi-generator-cli-3.4.4.jar generate -i public/doc/opeanpi-3-v0.0.2.json.generator.yaml -c .openapi_generator_config.json -g ruby -o topological_inventory-ingress_api-client-ruby

https://github.com/ManageIQ/topological_inventory-ingress_api/blob/master/.openapi_generator_config.json

with version 4.0.0 validator generates 100+ errors, version 4.1+ must be run with --skip-validate-spec

Steps to reproduce

TopologicalInventoryIngressApiClient::ServiceOffering.new(:source_ref => '123', :name => 'Sample',...).to_hash
TopologicalInventoryIngressApiClient::ServiceOffering.new(:source_ref => '123', :name => nil,...).to_hash

Related issues/PRs

Suggest a fix

Following line causes that keys with nil values are deleted, so it's not possible to recognize by server if they're not set or set to nil.

https://github.com/ManageIQ/topological_inventory-ingress_api-client-ruby/blob/8e685e8ae6b50afa69d6aa67284eea64e6da9c9b/lib/topological_inventory-ingress_api-client/models/inventory_collection_service_offering.rb#L199

This client is generated by version 4.2.0