[java][jackson] fix: conditionally add jackson JsonIgnoreProperties for base class polymorphism fixes #12777 #22527

[dnowo]

Adresses issues:

• [BUG][JAVA] discriminator ignored during serialization #12777
• Bug: Custom serialization/deserialization using Jackson ObjectMapper is impossible due to ignoring discrimination type getter #22527

Flag added to config:
disableDiscriminatorFieldIgnore -> if true, it ignores, does not creates jakarta @JsonIgnoreProperties in parent class like so:

/**
 * BaseConfiguration
 */
@JsonPropertyOrder({
  BaseConfiguration.JSON_PROPERTY_ID,
  BaseConfiguration.JSON_PROPERTY_TYPE
})
@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2025-12-10T23:17:17.750816900+01:00[Europe/Warsaw]", comments = "Generator version: 7.18.0-SNAPSHOT")

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
@JsonSubTypes({
  @JsonSubTypes.Type(value = ChildOneConfiguration.class, name = "CHILD_ONE"),
  @JsonSubTypes.Type(value = ChildTwoConfiguration.class, name = "CHILD_TWO"),
})

public class BaseConfiguration {
  public static final String JSON_PROPERTY_ID = "id";
  @javax.annotation.Nullable
  private Long id;

  public static final String JSON_PROPERTY_TYPE = "type";
  @javax.annotation.Nonnull
  private ConfigurationType type;

  public BaseConfiguration() { 
  }

@bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @martin-mfg (2023/08)

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[wing328]

CI issue not related to this change (samples already updated in latest master)

[wing328]

thanks for the PR

let's give it a try

[dschodits-secunet]

Thank you for doing all the work, I just have one suggestion/problem with this solution:
Due to the fact that the include parameter in the @JsonTypeInfo is still JsonTypeInfo.As.Property you run the risk of having the discriminator serialized twice. For example:
openapi.yaml:

    Pet:
      type: object
      discriminator:
        propertyName: petIntType
        mapping:
          0: '#/components/schemas/Dog'
          1: '#/components/schemas/Cat'
      properties:
        name:
          type: string
        petIntType:
          type: integer
      required:
        - name
    Cat: 
      description: A representation of a cat
      allOf:
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            huntingSkill:
              type: string
          required:
            - huntingSkill
    Dog: 
      description: A representation of a dog
      allOf:
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            packSize:
              type: integer
              format: int32
          required:
            - packSize

With this simple Javacode:

final var response = new Dog().petIntType(0).packSize(10).name("Dogo");
String ser = new ObjectMapper().writeValueAsString(response);
System.out.println("Seriliazied: " + ser)

Results in this:
Seriliazied: {"petIntType":"0","packSize":10,"name":"Dogo","petIntType":0}

My suggestion would be to use JsonTypeInfo.As.EXISTING_PROPERTY when disableDiscriminatorFieldIgnore is set to true. Something like this:

{{^disableDiscriminatorJsonIgnoreProperties}}
@JsonIgnoreProperties(
  value = "{{{discriminator.propertyBaseName}}}", // ignore manually set {{{discriminator.propertyBaseName}}}, it will be automatically generated by Jackson during serialization
  allowSetters = true // allows the {{{discriminator.propertyBaseName}}} to be set during deserialization
)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "{{{discriminator.propertyBaseName}}}", visible = true)
{{/disableDiscriminatorJsonIgnoreProperties}}

{{#disableDiscriminatorJsonIgnoreProperties}}
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "{{{discriminator.propertyBaseName}}}", visible = true)
{{/disableDiscriminatorJsonIgnoreProperties}}

This resolved the issue for me and I think it would not cause any problems, but I am happy to here any feedback!