ScriptEngine behaviour is non-standard and different to Nashorn

[nhoughto]

As per the Java Scripting API docs (https://docs.oracle.com/javase/7/docs/api/javax/script/ScriptContext.html) a ScriptEngine should honour the Scope of a Binding:

ENGINE_SCOPE: EngineScope attributes are visible during the lifetime of a single ScriptEngine and a set of attributes is maintained for each engine.
GLOBAL_SCOPE: GlobalScope attributes are visible to all engines created by same ScriptEngineFactory.

So I expect that an attribute set with a Global scope should be accessible to all engines from the same ScriptEngine, this does not appear to be the behaviour in graaljs though.

GraalJS code that fails:

        ScriptEngine eng = new ScriptEngineManager().getEngineByName("graal.js");
        eng.getBindings(ScriptContext.GLOBAL_SCOPE).put("globalThing", "asdf");
        Object globalResult = eng.eval("globalThing", eng.getBindings(ScriptContext.GLOBAL_SCOPE));
        Object engineResult = eng.eval("globalThing", eng.getBindings(ScriptContext.ENGINE_SCOPE));

with:

Exception in thread "main" javax.script.ScriptException: org.graalvm.polyglot.PolyglotException: ReferenceError: globalThing is not defined
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:199)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:176)
	at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)
	at Main.main(Main.java:15)
Caused by: org.graalvm.polyglot.PolyglotException: ReferenceError: globalThing is not defined
	at <js>.:program(<eval>:1)
	at org.graalvm.polyglot.Context.eval(Context.java:313)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:197)
	... 3 more

Same code with nashorn engine that works:

        ScriptEngine eng = new ScriptEngineManager().getEngineByName("nashorn");
        eng.getBindings(ScriptContext.GLOBAL_SCOPE).put("globalThing", "asdf");
        Object globalResult = eng.eval("globalThing", eng.getBindings(ScriptContext.GLOBAL_SCOPE));
        Object engineResult = eng.eval("globalThing", eng.getBindings(ScriptContext.ENGINE_SCOPE));

I'm looking into JSR223 APIs as i'm trying to find a clean way of either sharing values across Graal Contexts or "resetting" a context after an execution and Bindings / Scopes seem a good way to do it, relates to oracle/graal#631

[nhoughto]

This fixed by RC11?

https://github.com/graalvm/graaljs/blob/master/CHANGELOG.md#version-100-rc11

Added support for ScriptEngine GLOBAL_SCOPE bindings.? 🙏

[wirthi]

Hi @nhoughto

yes, we believe this is fixed in RC11. Would be great if you could confirm that.

-- Christian

[nhoughto]

Does that mean that sharing objects fully across contexts has changed too?

My other linked issue: oracle/graal#631

[nhoughto]

Works! 👍

[nhoughto]

So much like oracle/graal#631, only primitive values can be shared, and only in some scenarios. I'm not quite sure what all those scenarios are yet either, there is some odd behaviour.

Two failing scenarios:
Creating an object via eval() and then retrieving it again later in a subsequent eval():

	@Test
    public void testJSMapInScope() throws ScriptException {
        ScriptEngine eng = new ScriptEngineManager().getEngineByName(engineName);
        Bindings global = eng.getBindings(ScriptContext.GLOBAL_SCOPE);
        eng.eval("jsObj = {a: 1}", global);
        Object globalResult = eng.eval("JSON.stringify(jsObj)", global);
        System.out.println("globalResult: " + globalResult);
        Assert.assertNotNull(globalResult);
    }

GraalVM rc11

javax.script.ScriptException: org.graalvm.polyglot.PolyglotException: ReferenceError: jsObj is not defined

	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:207)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:179)
	at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)
	at MainTest.testJSMapInScope(MainTest.java:28)
Caused by: org.graalvm.polyglot.PolyglotException: ReferenceError: jsObj is not defined
	at <js>.:program(<eval>:1)
	at org.graalvm.polyglot.Context.eval(Context.java:335)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:205)
	... 25 more

nashorn:
globalResult: {"a":1}

Creating a JS map, putting it to the global scope (shouldnt be required, JS eval should have done it already, likely due to first scenario problem), then retrieve from the engine scope:

	@Test
    public void testJSMapInAcrossScope() throws ScriptException {
        ScriptEngine eng = new ScriptEngineManager().getEngineByName(engineName);
        Bindings global = eng.getBindings(ScriptContext.GLOBAL_SCOPE);
        global.put("jsObj", eng.eval("var map = {}; map", global));
        eng.eval("jsObj.a = 1", global);
        Object globalResult = eng.eval("JSON.stringify(jsObj)", global);
        System.out.println("globalResult: " + globalResult);
        Assert.assertNotNull(globalResult);

        Bindings engine = eng.getBindings(ScriptContext.ENGINE_SCOPE);
        Object engineResult = eng.eval("JSON.stringify(jsObj)", engine);
        System.out.println("engineResult: " + engineResult);
        Assert.assertNotNull(engineResult);
    }

GraalVM rc11

globalResult: {a: 1, b: "asdf"}
Exception in thread "main" javax.script.ScriptException: org.graalvm.polyglot.PolyglotException: java.lang.IllegalArgumentException: The value 'DynamicObject<JSUserObject>@79da8dc5' cannot be passed from one context to another. The current context is 0x1eb5174b and the argument value originates from context 0x67080771.
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:207)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:179)
	at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)
	at Main.main(Main.java:18)
Caused by: org.graalvm.polyglot.PolyglotException: java.lang.IllegalArgumentException: The value 'DynamicObject<JSUserObject>@79da8dc5' cannot be passed from one context to another. The current context is 0x1eb5174b and the argument value originates from context 0x67080771.
	at <js>.:program(Unknown)
	at org.graalvm.polyglot.Context.eval(Context.java:335)
	at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:205)
	... 3 more

Nashorn

globalResult: {"a":1}
engineResult: {"a":1}

[djoooooe]

This should be fixed as of RC 15, but the restrictions of oracle/graal#631 still apply.

[nhoughto]

Ok great, so which part has changed? 🤔The sharing of objects between scriptEngine scopes works now?

[nhoughto]

ah ok this works now:

ScriptEngine eng = new ScriptEngineManager().getEngineByName("graal.js");
        eng.getBindings(ScriptContext.GLOBAL_SCOPE).put("globalThing", "asdf");
        Object globalResult = eng.eval("globalThing", eng.getBindings(ScriptContext.GLOBAL_SCOPE));
        Object engineResult = eng.eval("globalThing", eng.getBindings(ScriptContext.ENGINE_SCOPE));

but can only be primitive types, otherwise get a cannot be passed from one context to another error. Is there an intention to allow that? oracle/graal#631 is still open so i assume it isn't out of the question?

[djoooooe]

It's still on the roadmap, but we don't have a definitive ETA yet.