Concurrent Modification to currentLoader: Cannot invoke "java.lang.ClassLoader.getParent()" because "this.currentLoader" is null

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Description

While executing the process-asciidoc goal on a project of mine, I encountered this error:

Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.ClassLoader.getParent()" because "this.currentLoader" is null
    at java.util.ServiceLoader$ModuleServicesLookupIterator.hasNext (ServiceLoader.java:1075)
    at java.util.ServiceLoader$2.hasNext (ServiceLoader.java:1309)
    at java.util.ServiceLoader$3.hasNext (ServiceLoader.java:1393)
    at org.asciidoctor.jruby.log.internal.LogHandlerRegistryExecutor.registerAllLogHandlers (LogHandlerRegistryExecutor.java:19)
    at org.asciidoctor.jruby.internal.JRubyAsciidoctor.registerLogHandlers (JRubyAsciidoctor.java:112)
    at org.asciidoctor.jruby.internal.JRubyAsciidoctor.processRegistrations (JRubyAsciidoctor.java:92)
    at org.asciidoctor.jruby.internal.JRubyAsciidoctor.create (JRubyAsciidoctor.java:69)
    at org.asciidoctor.jruby.internal.JRubyAsciidoctor.create (JRubyAsciidoctor.java:65)
    at org.asciidoctor.jruby.AsciidoctorJRuby$Factory.create (AsciidoctorJRuby.java:29)
    at org.asciidoctor.maven.AsciidoctorMojo.getAsciidoctorInstance (AsciidoctorMojo.java:398)
    at org.asciidoctor.maven.AsciidoctorMojo.processSources (AsciidoctorMojo.java:214)
    at org.asciidoctor.maven.AsciidoctorMojo.processAllSources (AsciidoctorMojo.java:166)
    at org.asciidoctor.maven.AsciidoctorMojo.execute (AsciidoctorMojo.java:156)

After taking a look at the code that caused the error:

@Override
        public boolean hasNext() {
            while (nextProvider == null && nextError == null) {
                // get next provider to load
                while (!iterator.hasNext()) {
                    if (currentLoader == null) {
                        return false;
                    } else {
                        currentLoader = currentLoader.getParent();
                        iterator = iteratorFor(currentLoader);
                    }
                }

                // attempt to load provider
                ServiceProvider provider = iterator.next();
                try {
                    @SuppressWarnings("unchecked")
                    Provider<T> next = (Provider<T>) loadProvider(provider);
                    nextProvider = next;
                } catch (ServiceConfigurationError e) {
                    nextError = e;
                }
            }
            return true;
        }

it seems that there is an if statement that handles the case in which the currentLoader is null. And yet, currentLoader.getParent() failed with a null pointer exception. This makes me believe that the issue is related to multithreading.

Is it possible that this issue was handled in recent releases so we might need to upgrade to the latest release?

Environment information

asciidoctor-maven-plugin version: 2.2.2
asciidoctorj version: 2.5.3
Maven, Java and OS version: 3.8.4

asciidoctor / asciidoctor-maven-plugin

Concurrent Modification to currentLoader: Cannot invoke "java.lang.ClassLoader.getParent()" because "this.currentLoader" is null #821