OpenAPI Generator无法为可复用枚举生成枚举类问题求助

我有一份OpenAPI 3.0.3规范的YAML文件，其中定义了如下可复用字符串枚举：

ParentPlanState:
  type: string
  enum:
    - NOT_PLANNABLE
    - PLANNABLE
    - REQUEST_EXTRA_DAY
    - REQUEST_EXTRA_DAY_DURING_HOLIDAY

该枚举在其他对象中通过如下方式引用：

planState:
  $ref: '#/ParentPlanState'

当枚举定义为不可复用形式时，OpenAPI Generator能生成正确的枚举类；但采用上述可复用定义时，生成的Android端代码是一个空的ParentPlanState类：

import io.swagger.annotations.ApiModel;
import java.io.Serializable;

@ApiModel(
    description = ""
)
public class ParentPlanState implements Serializable {
    public ParentPlanState() {
    }

    public boolean equals(Object o) {
        if (this == o) {
            return true;
        } else if (o != null && this.getClass() == o.getClass()) {
            ParentPlanState parentPlanState = (ParentPlanState)o;
            return true;
        } else {
            return false;
        }
    }

    public int hashCode() {
        int result = 17;
        return result;
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("class ParentPlanState {\n");
        sb.append("}\n");
        return sb.toString();
    }
}

而我期望生成的是类似jaxrs-resteasy-eap端的枚举类：

import java.util.Objects;
import java.util.ArrayList;
import com.fasterxml.jackson.annotation.JsonValue;
import java.io.Serializable;
public enum ParentPlanState {
  NOT_PLANNABLE,
  PLANNABLE,
  REQUEST_EXTRA_DAY,
  REQUEST_EXTRA_DAY_DURING_HOLIDAY;
}

请问有解决该问题的方法吗？谢谢！

内容的提问来源于stack exchange，提问作者user602896