Gradle projects fail with 'org.codehaus.groovy.runtime.GStringImpl cannot be cast to class java.lang.String'

[rudihorn]

As far as I can tell, jdtls fails when working with gradle strings that may refer to other variables. The simplest way for me to reproduce this error was to take a sample micronaut application from https://micronaut.io/launch/ (4.0.1, Java, Gradle, JUnit) and to then add the following snippet to build.gradle:

tasks.withType(JavaCompile) {
    options.compilerArgs.addAll([
        "-parameters",
        "-Amicronaut.processing.group=$project.group",
        "-Amicronaut.processing.module=$project.name",
    ])
}

Jdtls then fails with the following error:

Jul 28, 2023, 10:01:40 AM Initialization failed 
class org.codehaus.groovy.runtime.GStringImpl cannot be cast to class java.lang.String (org.codehaus.groovy.runtime.GStringImpl is in unnamed module of loader org.gradle.tooling.internal.provider.serialization.ClientSidePayloadClassLoaderFactory$MixInClassLoader @31b2fcee; java.lang.String is in module java.base of loader 'bootstrap')
java.lang.ClassCastException: class org.codehaus.groovy.runtime.GStringImpl cannot be cast to class java.lang.String (org.codehaus.groovy.runtime.GStringImpl is in unnamed module of loader org.gradle.tooling.internal.provider.serialization.ClientSidePayloadClassLoaderFactory$MixInClassLoader @31b2fcee; java.lang.String is in module java.base of loader 'bootstrap')
	at org.eclipse.jdt.ls.core.internal.managers.GradleUtils.parseProcessorOptions(GradleUtils.java:248)
	at org.eclipse.jdt.ls.core.internal.managers.GradleBuildSupport.syncAnnotationProcessingConfiguration(GradleBuildSupport.java:201)
	at org.eclipse.jdt.ls.core.internal.managers.GradleUtils.synchronizeAnnotationProcessingConfiguration(GradleUtils.java:288)
	at org.eclipse.jdt.ls.core.internal.managers.GradleProjectImporter.importToWorkspace(GradleProjectImporter.java:289)
	at org.eclipse.jdt.ls.core.internal.managers.ProjectsManager.importProjects(ProjectsManager.java:152)
	at org.eclipse.jdt.ls.core.internal.managers.ProjectsManager.initializeProjects(ProjectsManager.java:114)
	at org.eclipse.jdt.ls.core.internal.handlers.InitHandler$1.runInWorkspace(InitHandler.java:256)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:43)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

class org.codehaus.groovy.runtime.GStringImpl cannot be cast to class java.lang.String (org.codehaus.groovy.runtime.GStringImpl is in unnamed module of loader org.gradle.tooling.internal.provider.serialization.ClientSidePayloadClassLoaderFactory$MixInClassLoader @31b2fcee; java.lang.String is in module java.base of loader 'bootstrap')[Error]

Removing the strings "-Amicronaut.processing.group=$project.group" and "-Amicronaut.processing.module=$project.name" makes the problem go away.