[BUG] Using copyJacksonAnnotationsToAccessors=true in Eclipse causes build errors because Jackson tags are duplicated

[erizzo-cfa]

Describe the bug
A project I work on has recently updated to Lombok 1.18.40 and enabled the config option lombok.copyJacksonAnnotationsToAccessors=true. The reason we needed to set that config to true is subtle but has to do with the fact that many of our modules also have lombok.accessors.chain=true (which makes the setters "non-standard" in JavaBeans terms). But I'm not here to discuss that setting - it's required in our context because of backwards compatibility with the enormous number of projects we have to support.

Anyway, there were no problems in either our maven builds or in IntelliJ IDEA. However, in Eclipse (latest release 2025-09, with latest Lombok plugin, v1.18.42) it produces many build errors like this:

Duplicate annotation of non-repeatable type @JsonProperty. Only annotation types marked @Repeatable can be used multiple times at one target.

This seems like a reasonable result, especially when I delombok the code, because the @JsonProperty (and other Jackson annotations, this doesn't only happen with JsonProperty annotation) are present on both the fields and the lombok-generated getters.

What's odd is that it does not cause build problems in IntelliJ or command-line builds with maven. Additionally, our hundreds (maybe thousands) of tests pass just fine, including numerous integration tests that exercise Jackson serialization and deserialization.

To Reproduce
Set up lombok.config with lombok.copyJacksonAnnotationsToAccessors=true.
Create a class like the one below in Eclipse with Lombok plugin installed.

@Data
public class Person {

    @JsonProperty("name")
    private String name;

}

You'll see a build error in the Problems view about the @JsonProperty being repeated.
For example:

Open the same class in IntelliJ and there is no build error. Build it with maven, also no error.

Expected behavior
Behavior should be consistent across maven, IntelliJ, and Eclipse.

[erizzo-cfa]

Interestingly, I just copied the de-lomboked source and put it in the main src location for a project, and Eclipse has no build errors even with the duplicated @JsonProperty annotations (on fields and accessors).
The de-lomboked code is like this:

@JsonIgnoreProperties(ignoreUnknown = true)
public class Person {
    @JsonProperty("name")
    private String name;

    @java.lang.SuppressWarnings("all")
    @lombok.Generated
    public Person() {
    }

    @JsonProperty("name")
    @java.lang.SuppressWarnings("all")
    @lombok.Generated
    public String getName() {
        return this.name;
    }

    /**
     * @return {@code this}.
     */
    @JsonProperty("name")
    @java.lang.SuppressWarnings("all")
    @lombok.Generated
    public Person setName(final String name) {
        this.name = name;
        return this;
    }

This explains why maven (javac) and IntelliJ build the code without errors. It suggests to me that the problem is not in the repetition of the annotations in the generated code, but the Eclipse Lombok plugin that isn't handling the situation correctly.

[erizzo-cfa]

Attaching a sample project that can be imported into Eclipse or STS.

LombokJacksonAnnotationBug.zip

[rzwitserloot]

The error indicates that the same element has more than 1 annotation. Lombok is (somehow, partly) responsible for some element, I'm guessing the method, ending up in the AST as:

@JsonProperty("name")
@JsonProperty("name")
public Person setName(...)

It's not about both the field and the method existing and both of em having a JsonProperty annotation; that might be a problem, but not the kind of problem that results in the error "That is not @Repeatable".

Presumably the exact timing of the annotation-repeat check and when lombok copies things is different between the java and the eclipse handler.

[erizzo-cfa]

It's not about both the field and the method existing and both of em having a JsonProperty annotation; that might be a problem, but not the kind of problem that results in the error "That is not @Repeatable".

Presumably the exact timing of the annotation-repeat check and when lombok copies things is different between the java and the eclipse handler.

I agree (see my follow-up comment above). Question is, can that be fixed? Right now I've had no choice but to disable lombok.copyJacksonAnnotationsToAccessors locally in my projects, but that causes certain serialization tests to fail and I have to remember not to check in the change.

[erizzo-cfa]

Any thoughts on whether this can be fixed?

[janrieke]

That has been fixed in #3963 (waits for approval and merge from the maintainers).

[erizzo-cfa]

@rzwitserloot or @rspilker (or anyone else with review privileges), can I persuade you to review Jan's PR linked above? It's more than a month old and (supposedly) fixes this bug that breaks Lombok in Eclipse.