Add `ElementType.PARAMETER` to `@JsonIgnore` to allow use for Constructor parameters

[cowtowncoder]

(note: off-shoot of https://github.com/FasterXML/jackson-databind/issues/4626)

Looks like @JsonIgnore cannot be used on method/constructor parameters: latter can be problematic with Record types in particular (but also regulard POJOs' Constructors or Factory methods). So let's add that in 2.18.

[yihtserns]

One would expect Kotlin Data Class to handle annotations the same as Java Records, i.e. propagate annotation to fields and/or getters and/or constructor parameters depending on @Target, but apparently not.

Looking at the decompiled Kotlin Data Class, something like this:

data class BooleanPropertyInBody(@JsonIgnore val placeholder: String = "placeholder") { ... }

• Before this change: @JsonIgnore added on the generated field.
• After this change: @JsonIgnore added only on the constructor parameter. 🤨

UPDATE

Annoying - from https://kotlinlang.org/docs/annotations.html#annotation-use-site-targets:

If you don't specify a use-site target, the target is chosen according to the @Target annotation of the annotation being used. If there are multiple applicable targets, the first applicable target from the following list is used:

• param
• property
• field

[yihtserns]

Ugh, I missed out an important fact in https://github.com/FasterXML/jackson-databind/issues/4626:

1. @JsonIgnore's @Target not including ElementType.PARAMETER is only one-half of the problem.
2. prop.addCtor(..., false) <--- this hardcoded false in POJOPropertiesCollector is the other half of the problem.

Sorry!

[cowtowncoder]

Uggh. As little as I like the idea, maybe I should revert this change. WDYT @yihtserns .

But at least it was possible to pinpoint this change as the root cause for failing tests.

[yihtserns]

I think it's fine to revert at the first sign of problem - I believe you have more important things to focus on than this (+ to reduce any unnecessary risk for the upcoming 2 18 release).

And it's not like this is something urgent or requested, we can always do it later if we really want to.

[cowtowncoder]

PR reverted.

[bolds07]

I myself was going to open a request for this feature cuz it is very useful specially when using lombok to have @AllArgsConstructor

Or at least have an Ignore unkwon properties that really work. ex

@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class C{ 
   @JsonIgnore 
   private Board board;

      @JsonProperty(value = "title")
    private String title;


     @JsonProperty(value = "position")
    private int position;
}

then if i try

objectMapper.readValue("{\"title\":\"title\",\"position\":2}",C.class);

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Invalid type definition for type `C`: Argument #0 of constructor [constructor for `C` (3 args), annotations: [null] has no property name annotation; must have name when multiple-parameter constructor annotated as Creator
 at [Source: (String)"{"title":"title","position":2}"; line: 1, column: 1]

as far as i know there is no way to solve this without creating a custom deserializer or manually creating a constructor with @JsonCreator and both options are really inconvenient...

would be appreciated have an way to solve it with aspects or at least in the configuration of ObjectMapper

[cowtowncoder]

Unfortunately not sure we can proceed with this.

[deshack]

@bolds07 your example would work with the addition of @NoArgsConstructor. The problem here is not due to ignored properties, but constructor signature.