Hi Sundararajan,
I created this gist with syntax highlighting for better readability:
https://gist.github.com/jfrantzius/db6474f87300b45c887cdc2e45cd2dff
testObjectCreateInFunctionFails() shows where eval() seems to wrongly assume a
different global and wraps unnecessarily.
Regards,
Jörg
> Am 01.03.2017 um 09:27 schrieb Frantzius, Jörg <joerg.frantz...@aperto.com>:
>
> Hi Sundarajan,
>
> thx a lot for the explanations, this cleared the picture much for me.
>
> If you look at the second code snippet, though, it is not obvious where there
> should be any crossing of global boundaries:
>
> SimpleScriptContext context = new SimpleScriptContext();
> context.setAttribute("f", engine.eval("(function ()
> {Object.create(this)})"), ScriptContext.ENGINE_SCOPE);
> engine.eval("f.call({})", context);
>
> Here the function object is put into a ScriptContext that is then also passed
> to eval() for invoking it, so there is no second ScriptContext involved. This
> is in contrast to the first code snippet, where there is both a
> SimpleBindings object and the engine’s default ScriptContext.
>
> By the way, if the last line passes „f" as „this“ instead of a new object
> „{}":
>
> engine.eval("f.call(f)", context);
>
> Then the test succeeds. So the new object „{}“ seems to be associated with a
> different global than that of the given ScriptContext, or at least Nashorn
> thinks so?
>
> Does that mean eval() keeps or creates a global also when it is given a
> ScriptContext or Bindings argument? Or is there maybe some wrapping going on
> here that shouldn’t happen?
>
> Regards,
> Jörg
>
> Am 01.03.2017 um 06:39 schrieb Sundararajan Athijegannathan
> <sundararajan.athijegannat...@oracle.com<mailto:sundararajan.athijegannat...@oracle.com>>:
>
> Hi,
>
> In Nashorn, each ENGINE_SCOPE Bindings instance is associated with it's own
> Nashorn global instance (an instance of jdk.nashorn.internal.objects.Global
> class). i.e., each ENGINE_SCOPE Bindings instance is associated with a fresh
> ECMAScript/JS global scope object - with it's own "Object", "Function",
> "RegExp" etc.
>
> Nashorn represents script objects crossing JS global boundary as
> ScriptObjectMirror instances. ScriptObjectMirror is also the way Java code
> can access any script object (without having to deal with internal
> jdk.nashorn.internal.runtime.ScriptObject). See also:
> https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/ScriptObjectMirror.html
>
> If you access a script object from a JS global scope g1 from another JS
> global scope g2, you'll get a ScriptObjectMirror wrap. Nashorn attempts to
> provide seamless integration of ScriptObjectMirror instances - you can treat
> ScriptObjectMirrors almost like those are script objects. But this
> integration is not complete. Please see also:
> https://wiki.openjdk.java.net/display/Nashorn/Nashorn+jsr223+engine+notes
>
> Not every JS API can work with ScriptObjectMirrors (like these APIs work with
> script objects that belong to the "current" JS global scope). Object.create
> is one such API. You can adjust your code slightly. For example:
>
> import javax.script.*;
> import jdk.nashorn.api.scripting.*;
>
> public class Main {
> public static void main(String[] args) throws Exception {
> ScriptEngine e = new ScriptEngineManager().getEngineByName("nashorn");
> e.put("foo", e.eval("function() { return {} }", new SimpleBindings()));
> // get "foo"
> ScritptObjectMirror foo = (ScriptObjectMirror)e.get("foo");
> // eval Object.create in the global where "foo" belongs - with "foo"
> set as "this"
> System.out.println(foo.eval("Object.create(this)"));
> }
> }
>
> Hope this helps,
> -Sundar
>
> On 01/03/17, 2:35 AM, Frantzius, Jörg wrote:
> Hi,
> in my code I’m running into an issue for which
> https://github.com/coveo/nashorn-commonjs-modules/issues/3 luckily provides a
> snippet for reproducing:
>
> @Test
> public void testObjectCreateOnFunction() throws ScriptException {
> ScriptEngine engine = new
> ScriptEngineManager().getEngineByName("nashorn");
> engine.put("foo", engine.eval("function() { return {}; }", new
> SimpleBindings()));
> engine.eval("Object.create(foo());");
> }
>
> This fails with:
>
> Caused by:<eval>:1 TypeError: [object Object] is not an Object
> at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57)
> at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:213)
> at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:185)
> at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:172)
> at jdk.nashorn.internal.objects.Global.checkObject(Global.java:2073)
> at jdk.nashorn.internal.objects.NativeObject.create(NativeObject.java:261)
> at jdk.nashorn.internal.scripts.Script$21$\^eval\_.:program(<eval>:1)
> at
> jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:623)
> at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
> at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
> at
> jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:446)
> ... 31 more
>
> In my own code, the pattern is slightly different, but it fails similarly
> (SimpleScriptContext internally uses SimpleBindings as well):
>
> @Test
> public void testObjectCreateInFunction() throws ScriptException {
> ScriptEngine engine = new
> ScriptEngineManager().getEngineByName("nashorn");
> SimpleScriptContext context = new SimpleScriptContext();
> context.setAttribute("f", engine.eval("(function ()
> {Object.create(this)})"), ScriptContext.ENGINE_SCOPE);
> engine.eval("f.call({})", context);
> }
>
> The issue seems to be that the function object internally isn’t turned from
> ScriptObjectMirror into ScriptObject, so Global.checkObject() fails.
>
> I’d be thankful for any hints on whether this may be a bug or intended
> behaviour.
>
> Regards,
> Jörg
>
>
> ---
>
> Dipl. Inf. Jörg von Frantzius, Technical Director
>
> E-Mail joerg.frantz...@aperto.com<mailto:joerg.frantz...@aperto.com>
>
> Phone +49 30 283921-318
> Fax +49 30 283921-29
>
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>
>
>
> ---
>
> Dipl. Inf. Jörg von Frantzius, Technical Director
>
> E-Mail joerg.frantz...@aperto.com
>
> Phone +49 30 283921-318
> Fax +49 30 283921-29
>
> Aperto GmbH – An IBM Company
> Chausseestraße 5, D-10115 Berlin
> http://www.aperto.com<http://www.aperto.de/>
> http://www.facebook.com/aperto
> https://www.xing.com/companies/apertoag
>
> HRB 77049 B, AG Berlin Charlottenburg
> Geschäftsführer: Dirk Buddensiek, Kai Großmann, Stephan Haagen, Daniel Simon
---
Dipl. Inf. Jörg von Frantzius, Technical Director
E-Mail joerg.frantz...@aperto.com
Phone +49 30 283921-318
Fax +49 30 283921-29
Aperto GmbH – An IBM Company
Chausseestraße 5, D-10115 Berlin
http://www.aperto.com
http://www.facebook.com/aperto
https://www.xing.com/companies/apertoag
HRB 77049 B, AG Berlin Charlottenburg
Geschäftsführer: Dirk Buddensiek, Kai Großmann, Stephan Haagen, Daniel Simon
