ClassCastException for Lombok 1.6.22 and Gradle 4.8

[pkubowicz]

To reproduce:

Run gradle init --type java-library and modify generated project:

build.gradle

plugins { id 'java-library' }

dependencies {
    compileOnly 'org.projectlombok:lombok:1.16.22'
    annotationProcessor 'org.projectlombok:lombok:1.16.22'
}

compileJava {
    options.incremental = true
}

repositories {
    jcenter()
}

Foo.java

import lombok.Data;

@Data
public class Foo {
    private final boolean historical;
}

Running gradle build causes error:

> Task :compileJava FAILED
src/main/java/Library.java:4: warning: lombok.javac.apt.LombokProcessor could not be initialized. Lombok will not run during this compilation: java.lang.ClassCastException: org.gradle.api.internal.tasks.compile.processing.IncrementalFiler cannot be cast to com.sun.tools.javac.processing.JavacFiler
public class Library {
       ^
        at lombok.javac.apt.LombokProcessor.getJavacFiler(LombokProcessor.java:447)
        at lombok.javac.apt.LombokProcessor.init(LombokProcessor.java:90)
        at lombok.core.AnnotationProcessor$JavacDescriptor.want(AnnotationProcessor.java:112)
        at lombok.core.AnnotationProcessor.init(AnnotationProcessor.java:165)
        at lombok.launch.AnnotationProcessorHider$AnnotationProcessor.init(AnnotationProcessor.java:73)
        at org.gradle.api.internal.tasks.compile.processing.DelegatingProcessor.init(DelegatingProcessor.java:57)
        at org.gradle.api.internal.tasks.compile.processing.IsolatingProcessor.init(IsolatingProcessor.java:44)

Note that the error appears in file not annotated with Lombok annotations (created by gradle init).

Workaround - either:

1. Downgrade Lombok to 1.16.20 (implicitly disables incremental compilation); or
2. Downgrade Gradle to 4.7

[victorwss]

The title is wrong. It is not 1.6.12, it is 1.16.22.

What happens with 1.18.0?

[pkubowicz]

1.18.0 causes the same error with the same stacktrace.

[arana198]

I have a similar issue on all lombok "@"Data annotation. Example error:

../user/service/impl/UserServiceImpl.java:178: error: cannot find symbol
    userBO.getRoles()
          ^
  symbol:   method getRoles()
  location: variable userBO of type UserBO

I'm using:

• Java 10
• Lombok 1.18.0 (also tried 1.16.22)
• Gradle 4.8 (also tried with 4.7)

PS: I have requires static lombok in module-info.java and IDE does not show any error

[ryonday]

With:

• Oracle Java 9.0.4,
• Gradle 4.8
• Lombok 1.6.22 OR 1.18.0

I receive this error.

Reverting to Gradle 4.7 results in proper functionality.

[victorwss]

@arana198 Your problem seems to be something else unrelated to this. Perhaps #1572?

[soberich]

@pkubowicz @arana198 This started to show up again starting form Gradle 4.6 see #1603
@victorwss You've asked for MVCE there. So, finally we have a kind of it. It is hardly reproducible while I was trying to provide MVCE on a small project and minimal setup - it did not appear. Now this example is finally small and shows the issue.

[mszabo-wikia]

looks like Gradle internals changed in 4.8, necessitating some case handling— ☝️ should address that

[victorwss]

Funny, this is the code where the error happens:

https://github.com/rzwitserloot/lombok/blob/master/src/core/lombok/javac/apt/LombokProcessor.java#L429-L448:

	/**
	 * This class casts the given filer to a JavacFiler. In case of
	 * gradle incremental compilation, the delegate Filer of the gradle wrapper is returned.
	 */
	public JavacFiler getJavacFiler(Filer filer) {
		final Class<?> filerSuperClass = filer.getClass().getSuperclass();
		if (filerSuperClass.getName().equals("org.gradle.api.internal.tasks.compile.processing.IncrementalFiler")) {
			try {
				Field field = filerSuperClass.getDeclaredField("delegate");
				field.setAccessible(true);
				Object delegate = field.get(filer);
				return (JavacFiler) delegate;
			} catch (final Exception e) {
				e.printStackTrace();
				processingEnv.getMessager().printMessage(Kind.WARNING,
						"Can't get the delegate of the gradle IncrementalFiler. Lombok won't work.");
			}
		}
		return (JavacFiler) filer;
	}

The code is clearly aware of gradle's IncrementalFiler, but something was wrong anyway. It tests if the filer has IncrementalFiler as the direct superclass, but the error message suggests that it is a direct instance of IncrementalFiler and not a subclass of that.

Also, that if a reflection exception happens and is caught in the exception handler, a ClassCastException will be throw in the end of the method, but this is not the real problem.

[victorwss]

Also, the code could test if the filer is something that is neither JavacFiler nor IncrementalFiler, giving a better error message in this case to help us with future debugging and issue reporting.

[pkubowicz]

Can you release this soon?

In Gradle 4.9 you cannot use Lombok 1.18.0 or 1.16.22 at all - not even for non-incremental compilation (tested on the same project configuration as in the original bug report).

To get Java sources compiled with Gradle 4.9 you need to downgrade to Lombok 1.16.20.

[gerritdrost]

Gradle 4.9 just hit the Arch Linux repo, so I suspect more people will start suffering from this.

[sergey-morenets]

After upgrade to Gradle 4.9 my project failed to compile.

JDK 10.0.1
Lombok 1.18.0

warning: lombok.javac.apt.LombokProcessor could not be initialized. Lombok will not run during this compilation: java.lang.ClassCastException: org.gradle.api.internal.tasks.compile.processing.IncrementalFiler cannot be cast to jdk.compiler/com.sun.tools.javac.processing.JavacFiler
public class ExceptionHandler {
       ^
        at lombok.javac.apt.LombokProcessor.getJavacFiler(LombokProcessor.java:447)
        at lombok.javac.apt.LombokProcessor.init(LombokProcessor.java:90)
        at lombok.core.AnnotationProcessor$JavacDescriptor.want(AnnotationProcessor.java:112)
        at lombok.core.AnnotationProcessor.init(AnnotationProcessor.java:165)

[sergey-morenets]

@pkubowicz Unfortunately I cannot downgrade Lombok to 1.16.20 because I use JDK 10 and this version doesn't support it