[BUG][Java] oneOf with enum discriminator fails to compile

[chuckbenger]

Description

When using the oneOf expression with enums the code fails to compile because the interface has a function of type "public String getType();", while the children nodes have the implemented method defined as "public TypeEnum getType() {}" which doesn't match the contract. If I manually change the concrete classes to match the interface (ex changing the TypeEnum method to public String getType() {
return type.value;
} it compiles and works fine.

I'm wondering if I'm doing something wrong or what.

Example Components

TargetingExpression:
      oneOf:
        - $ref: "#/components/schemas/TargetingPredicate"
        - $ref: "#/components/schemas/TargetingPredicateNested"
      discriminator:
        propertyName: "type"
        mapping:
          "views": "#/components/schemas/SDTargetingPredicateNested"
          "asinSameAs": "#/components/schemas/TargetingPredicate"

TargetingPredicate:
      type: "object"
      required: ["type", "value"]
      properties:
        type:
          type: "string"
          enum:
            - asinSameAs
        value:
          type: "string"

TargetingPredicateNested:
      type: "object"
      required: ["type", "value"]
      properties:
        type:
          type: "string"
          enum:
            - views
        value:
          type: "array"

Which then generates this

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2021-03-22T22:35:47.230-04:00[America/Toronto]")
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "type", visible = true)
@JsonSubTypes({
  @JsonSubTypes.Type(value = TargetingPredicate.class, name = "asinSameAs"),
  @JsonSubTypes.Type(value = TargetingPredicateNested.class, name = "views"),
})

public interface TargetExpression  {
    public String getType();
}

//==============
@JsonPropertyOrder({
  SDTargetingPredicateV31.JSON_PROPERTY_TYPE,
  SDTargetingPredicateV31.JSON_PROPERTY_VALUE
})
@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2021-03-22T22:35:47.230-04:00[America/Toronto]")
public class TargetingPredicate implements SDTargetExpression {
  /**
   * Gets or Sets type
   */
  public enum TypeEnum {
    ASINSAMEAS("asinSameAs");

    private String value;

    TypeEnum(String value) {
      this.value = value;
    }

    @JsonValue
    public String getValue() {
      return value;
    }

    @Override
    public String toString() {
      return String.valueOf(value);
    }

    @JsonCreator
    public static TypeEnum fromValue(String value) {
      for (TypeEnum b : TypeEnum.values()) {
        if (b.value.equals(value)) {
          return b;
        }
      }
      throw new IllegalArgumentException("Unexpected value '" + value + "'");
    }
  }

  public static final String JSON_PROPERTY_TYPE = "type";
  private TypeEnum type;

  public static final String JSON_PROPERTY_VALUE = "value";
  private String value;


  public TargetingPredicate type(TypeEnum type) {
    
    this.type = type;
    return this;
  }

   /**
   * Get type
   * @return type
  **/
  @NotNull
  @ApiModelProperty(required = true, value = "")
  @JsonProperty(JSON_PROPERTY_TYPE)
  @JsonInclude(value = JsonInclude.Include.ALWAYS)

  public TypeEnum getType() {
    return type;
  }


  public void setType(TypeEnum type) {
    this.type = type;
  }


  public TargetingPredicate value(String value) {
    
    this.value = value;
    return this;
  }

   /**
   * The value to be targeted.
   * @return value
  **/
  @NotNull
  @ApiModelProperty(example = "B0123456789", required = true, value = "The value to be targeted.")
  @JsonProperty(JSON_PROPERTY_VALUE)
  @JsonInclude(value = JsonInclude.Include.ALWAYS)

  public String getValue() {
    return value;
  }


  public void setValue(String value) {
    this.value = value;
  }


  @Override
  public boolean equals(java.lang.Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    TargetingPredicate TargetingPredicate = (SDTargetingPredicateV31) o;
    return Objects.equals(this.type, TargetingPredicate.type) &&
        Objects.equals(this.value, TargetingPredicate.value);
  }

  @Override
  public int hashCode() {
    return Objects.hash(type, value);
  }


  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("class SDTargetingPredicateV31 {\n");
    sb.append("    type: ").append(toIndentedString(type)).append("\n");
    sb.append("    value: ").append(toIndentedString(value)).append("\n");
    sb.append("}");
    return sb.toString();
  }

  /**
   * Convert the given object to string with each line indented by 4 spaces
   * (except the first line).
   */
  private String toIndentedString(java.lang.Object o) {
    if (o == null) {
      return "null";
    }
    return o.toString().replace("\n", "\n    ");
  }

}

Configuration

{
  "useBeanValidation": "true",
  "serializationLibrary": "jackson",
  "library": "jersey2",
  "java8": "true",
  "dateLibrary": "java8",
  "sourceFolder": "",
  "modelPackage": "com.models,
  "legacyDiscriminatorBehavior": false
}

openapi-generator version

Openapi-generator-4.3.1

[wing328]

Please try newer stable version v5.1.0 instead.

[valmoz]

Hi, I have the same issue with version 5.4.0.

This is my enum:

title: CashbookEntryType
type: string
nullable: true
enum:
  - in
  - out
description: Cashbook type.

And here's my model:

title: CashbookEntry
oneOf:
  - $ref: ./CashbookEntryIn.yaml
  - $ref: ./CashbookEntryOut.yaml
discriminator:
  propertyName: type
  mapping:
    in: ./CashbookEntryIn.yaml
    out: ./CashbookEntryOut.yaml

The problem is on the generated constructor:

public CashbookEntry() {
    this.type = this.getClass().getSimpleName();
  }

This is valid only for String discriminators, not with Enum ones.
The correct version for Enum discriminators is the following one, using the fromValue method of the enum type:

public CashbookEntry() {
    this.type = CashbookEntryType.fromValue(this.getClass().getSimpleName());
  }

For now, I fixed creating a custom template and using this (really ugly, I added a futile loop on vars) fragment to modify the generated constructor method:

{{#discriminator}}
  public {{classname}}() {
    {{#vars}}
    {{#isDiscriminator}}
    {{#isString}}
    this.{{{discriminatorName}}} = this.getClass().getSimpleName();
    {{/isString}}
    {{^isString}}
    this.{{{discriminatorName}}} = {{{datatypeWithEnum}}}.fromValue(this.getClass().getSimpleName());
    {{/isString}}
    {{/isDiscriminator}}
    {{/vars}}
  }
  {{/discriminator}}

but it would be way better to add a field to the "discriminator" variable to be able to select the correct instruction to insert in the generated code.

[arvindkrishnakumar-okta]

Is this going to be fixed sometime soon?