NPE in CompilerConfiguration

[torsten-witte]

The following code results in a NullPointerException:

ClassLoader classLoader = ...
String url = ...
GroovyScriptEngine engine = new GroovyScriptEngine(url, classLoader);

Here is the stack trace:

java.lang.NullPointerException
	at java.util.Collections$UnmodifiableMap.<init>(Unknown Source)
	at java.util.Collections.unmodifiableMap(Unknown Source)
	at org.codehaus.groovy.control.CompilerConfiguration$1.getJointCompilationOptions(CompilerConfiguration.java:147)
	at org.codehaus.groovy.control.CompilerConfiguration.<init>(CompilerConfiguration.java:481)
	at groovy.util.GroovyScriptEngine.<init>(GroovyScriptEngine.java:96)
	at groovy.util.GroovyScriptEngine.<init>(GroovyScriptEngine.java:495)
	at groovy.util.GroovyScriptEngine.<init>(GroovyScriptEngine.java:503)

The problem is that CompilerConfiguration.DEFAULT.getJointCompilationOptions() wants to create an unmodifiable map with null (jointCompilationOptions is always null at this point).
The error is included since commit b03ff24c8f43088b6edadb1adcf17f7a945d6563.

public class CompilerConfiguration {
    ...
    public static final CompilerConfiguration DEFAULT = new CompilerConfiguration() {
        ...
        @Override
        public Map<String, Object> getJointCompilationOptions() {
                return Collections.unmodifiableMap(super.getJointCompilationOptions());  // <------- NullPointerException
        }
        ...
    }

    /**
     * options for joint compilation (null by default == no joint compilation)
     */
    private Map<String, Object> jointCompilationOptions;

    public CompilerConfiguration(CompilerConfiguration configuration) {
        ...
        Map<String, Object> jointCompilationOptions = configuration.getJointCompilationOptions();
        if (jointCompilationOptions != null) {
            jointCompilationOptions = new HashMap<String, Object>(jointCompilationOptions);
        }
       ...
    }

    public Map<String, Object> getJointCompilationOptions() {
        return jointCompilationOptions;
    }
    ...
}

Here is an easier way to reproduce:

CompilerConfiguration defaultConfig = CompilerConfiguration.DEFAULT;
System.out.println("JointCompilationOptions: " + defaultConfig.getJointCompilationOptions());