@Sundararajan I ran into an issue with a JSObject I implemented and some code in LessCSS. The team is likely aware by now of a need to return Undefined from JSObject's getMember() and possibly call(), and getSlot()... You had previously asked a long time ago why someone would want to do that and I responded here:
http://stackoverflow.com/questions/30528083/passing-undefined-to-nashorn-javascript-in-scala-java/30533897#30533897 with a comment: Why pass undefined? Let's say your calling an existing javascript lib (like lesscss) that calls something like this... var variables = options.variables; // keep in mind typeof null === 'object' and typeof undefined === 'undefined' if (typeof variables === 'object') { var keys = Object.keys(variables); //error 'null is not an Object' } Now to put into perspective, 'options' is an implementation of AbstractJSObject... how else would you specify in getMember that the member does not exist, returning null would throw an error when Object.keys() is called. I used this workaround... because in my sandbox that runs lesscss etc java accessibility is removed and I would not be able to make the callback... // Code Fragment if (Undefined.getUndefined() == null) { // Get the undefined object now, in its own script engine, to avoid problems with permissions/security factory.getScriptEngine().eval("Java.type('io.github.artfiedler.nashorn.Undefined').setUndefined(undefined);"); } /** * Used to reference the Undefined value used in nashorn. * * This is a standalone class to avoid a passing a reference * to an object like NashornSandbox to javascript that may be * exploited in some way unexpected way. */ public final class Undefined { private static Object undefinedObject; public static void setUndefined(Object undefined) { undefinedObject = undefined; } /** * Provides and easy way to get the undefined javascript value used by nashorn. * This value is not populated until after a NashornSandbox has been initialized * * @return the internal Nashorn object used to reference undefined */ public static Object getUndefined() { return undefinedObject; } } Now using my Undefined class I can do the following in my AbstractJSObject... and this will now support the existing lesscss code without modifications. @Override public Object getMember(String name) { return spill.getOrDefault(name, Undefined.getUndefined()); } I know that Undefined is defined at jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED && jdk.nashorn.internal.runtime.Undefined.getUndefined() and the team may not want to expose those specific classes to the API but I believe at least something like this should be done... @Exported public final class ScriptObjectMirror extends AbstractJSObject implements Bindings { // This already exists... public static boolean isUndefined(Object obj) { return obj == ScriptRuntime.UNDEFINED; } // Add... public static Object getUndefined() { return ScriptRuntime.UNDEFINED; } ... } -- or -- @Exported public interface JSObject { Object Undefined = ScriptRuntime.UNDEFINED; ... } -- or -- @Exported public interface JSObject { Object Undefined = new Object() { @Override public String toString() {return "undefined";} }; ... } // This would require any usages of JSObject to check for JSObject.Undefined coming out of getMember(), call(), getSlot(), eval(), newObject()
