Grab checkstyle issues in a configuration cache compatible way

build.gradle

abstract class CheckstyleReportAsCustomValueBuildService implements BuildService<CheckstyleReportAsCustomValueBuildService.Params>, OperationCompletionListener {

    interface Params extends BuildServiceParameters {
        ListProperty<FileSystemLocation> getReports()
        Property<BuildScanExtension> getBuildScanApi()
    }

    @Override
    void onFinish(FinishEvent finishEvent) {
        if(finishEvent.getDescriptor().displayName.contains("checkstyle")){
            println getParameters().getReports().get().forEach({
                if(it.asFile.exists()) {
                    def checkstyle = new XmlSlurper().parse(it.asFile)
                    def errors = checkstyle.file.collect {
                        String filePath = it.@name.text()
                        it.error.collect { "${filePath}:${it.@line}:${it.@column} \u2192 ${it.@message}" }
                    }.flatten()
                    println errors
                    errors.each { getParameters().getBuildScanApi().get().value('Checkstyle Issue', it) }
                }
            })
        }
    }
}

BuildScanExtension buildScanApi = project.extensions.findByName('buildScan')

SetProperty<FileSystemLocation> reportPaths = project.getObjects().setProperty(FileSystemLocation.class)

tasks.withType(Checkstyle) {
    reports {
        xml.required = true
        html.required = false
    }
    reportPaths.add(reports.xml.outputLocation.locationOnly)
}

def registry = project.services.get(BuildEventsListenerRegistry)
registry.onTaskCompletion(gradle.sharedServices.registerIfAbsent('checkstyleReportAsCustomValueBuildService', CheckstyleReportAsCustomValueBuildService.class, spec -> {
    spec.parameters.reports.set(reportPaths)
    spec.parameters.buildScanApi.set(buildScanApi)
}))