Lombok: Missing override annotation on generated methods

[FredPraca]

At work, we used to tag missing override annotations as errors.
When using @EqualsAndHashCode, the compiler complains about the lack of the @Override annotation.
The case also appears when having an interface declaring specific accessors.

Would it be possible to add this missing annotation when appropriate ?

[rzwitserloot]

I think we originally did not add it because it wasn't a legit move in java 1.5 or 1.6 for interfaces, except this isn't even an interface.

I really see no reason NOT to gen an @Override annotation. If anyone has a good reason not to do it, please do comment on this one!

[rzwitserloot]

We generate @Override; lombok's always done so. Possibly this is a bug in your IDE or linter tool or whatever it is. Can you elaborate on what kind of tool you're talking about here?

Without further feedback, this issue can be closed starting on March 31st.

[rzwitserloot]

NB: If it's about 'canEqual', we can't add @Override on these, unfortunately.

[mmoayyed]

One example can be noted here:

Where AbstractRandomStringGenerator is defined as:

@Getter
public abstract class AbstractRandomStringGenerator implements ... {
    private int defaultLength;

...
}

This is with Lombok 1.6.20 and Gradle's error-prone plugin 0.0.13 which I believe uses the latest version of error-prone at the time of this post. This may quite likely be an issue with error-prone, not sure.

[rspilker]

We cannot generate @Override here, since we cannot determine the methods in an interface. However, you cna have ombok generate @lombok.Generated by putting the following line in lombok.config:

lombok.addLombokGeneratedAnnotation = true

This should tell error-prone to not generate warnings on lombok generated methods.

[mmoayyed]

Thank you for the suggestions.

I believe that setting is and was already in place when I captured the screenshot. But I must admit I don't follow your note above: The method getDefaultLength is also part of the abstract class. Do the same rules apply there?

PS: If I actually delombok the @Getter annotation in the above abstract class, I see:

    public int getDefaultLength() {
        return this.defaultLength;
    }

[mmoayyed]

Ah, never mind. I see what you meant. Thanks for the hint! (It is curious though why the setting does not quire suppress the warnings)

[mithuns]

yeah, that setting does not seem to suppress warning generated by error-prone.

[ob-stripe]

I don't think Error Prone cares about the @lombok.Generated annotation, but you can configure Lombok[0] with:
```
lombok.addJavaxGeneratedAnnotation = true

and pass the `-XepDisableWarningsInGeneratedCode` flag to Error Prone[1]. This will only work with Java 8 though as the `@javax.annotation.Generated` is broken as of Java 9.

Alternatively, for getters and setters, you can manually tell Lombok to add the `@Override` annotation with the `onMethod` parameter[2]:
```java
@Getter(onMethod = @__({@Override})) @Setter(onMethod = @__({@Override})) String foo;

Unfortunately, at this time I don't think there's a Java 9 compatible solution for the canEqual methods generated by @EqualsAndHashCode.

@rzwitserloot Do you think it would be possible to add something like onMethod to @EqualsAndHashCode to solve this issue?

[0] https://projectlombok.org/features/configuration
[1] http://errorprone.info/docs/flags
[2] https://projectlombok.org/features/GetterSetter

[joaoe]

Hi.

I'm hitting this problem consistently

warning: [MissingOverride] canEqual overrides method in MyServiceRequestPayloadWithBody; expected @Override
@Data

I'm implementing a Rest service and have an hierarchy of objects which are mapped from JSON to POJOs using com.fasterxml.jackson.databind.ObjectMapper.

I also have some interfaces I use to abstract away each different object when implementing the business logic. Something like:

interface MyServiceObject extends Serializable {}

interface MyServiceRequest extends MyServiceObject {
  String getRequestId();
}

@Data
class MyServiceRequestPayload implements MyServiceRequest {
  private String eventId;
  private PauloadHeader header;
}

@Data
class MyServiceRequestPayloadWithBody extends MyServiceRequestPayload {
  private List<MyServiceObject > items;
}

The problem is that @Data and therefore @Getter and @EqualsAndHashCode are not aware of inherited methods. In this example, there is an abstract method getRequestId which comes from an interface and an implemented method canEqual which comes from @EqualsAndHashCode and is inherited from MyServiceRequestPayload to MyServiceRequestPayloadWithBody.

When compiling I get these warnings:

MyServiceRequestPayload.java: warning: [MissingOverride] getRequestId implements method in MyServiceRequest ; expected @Override
MyServiceRequestPayloadWithBody.java: warning: [MissingOverride] canEqual overrides method in MyServiceRequestPayload ; expected @Override

I'd really like if lombok was a bit smarter with these annotations and peeked into the hierarchy to see if there is a method with the same signature and if so, add the @Override. For me it's a bad practice to litter my code with @SuppressWarnings and using @Getter(onMethod_={@Override}) is boiler plate we should be avoiding.

I'm using IntelliJ. If I delombok the files, I see that the common methods like toString and equals do not have @Override. In my project we're using SonarQube and the Sonar Intellij plugin does complain too about those methods when I use @Data in a class hierarchy.

Thank you.

[rspilker]

Unfortunately we cannot look at the hierarchy, it requires resolution, see https://github.com/rzwitserloot/lombok/wiki/LOMBOK-CONCEPT:-Resolution

[joaoe]

Ah, I see. I did not know that lombok pre-compiled the files.

Then perhaps just add something extra that allows the developer to easily inject that @Override where needed ?

1. Regarding the case of overriding a setter:

It's easy to add a @Getter/Setter(onMethod_={@Override}) to the property String requestId. So that's covered, but it still requires a bit of boiler-plate, both on the class and property

I'd suggest something to simplify that case like at the class level @Getter(overrides={"requestId"}) class Klass{} or at the property level @GetterOverrides String requestId;

In case of a class level annotation, also allow that info to be passed from @Data like @Data(getterOverrides={"requestId"}, getterOverrides={})

2. Regarding @EqualsAndHashCode

I can't think of anything elegant, although I think it does not make sense to add some argument to the annotation just to hint lombok to add the @Override canEqual(). Perhaps adding @SuppressWarnings("MissingOverride") to the generated canEqual would be a way to shut up the compiler.

How about renaming that method to can<MyPackageMyKlassName>Equal() ? Does that break somehow the equals check in derived classes ? This would also result in more methods per class, but I doubt people make really long hierarchies with classes and @EqualsAndHashCode.

Extra: toString() and equals() stil need @Override there. I have SonarQube complaining on my project.

[kamilgregorczyk]

@SuppressWarnings("MissingOverride") to canEqual seems like a great idea

[hinrik]

@SuppressWarnings("MissingOverride") to canEqual seems like a great idea

Would this work? If so, is there any reason not to do it?

[cdir]

We also have trouble with missing @Override at canEqual Method and we need to disable the error for missing overrides in eclipse project settings.

I think it is safe to generate the @Override as long as I only subclass other objects that also have the canEqual method.

Maybe add an additional setting wether the @Override should alsways be generated at canEqual or not.

[barorion]

I don't think Error Prone cares about the @lombok.Generated annotation

This should be solved by https://github.com/google/error-prone/pull/2125.

So now error prone should be able to properly detect Lombok's generated code (assuming lombok.addJavaxGeneratedAnnotation = true is defined).