153497 - Problem comparing String to NativeString

Status: VERIFIED INVALID

(Rhino Graveyard :: Core, defect)

Description

[Laura Werner]

In Rhino 1.5r3, I ran across a problem evaluating a simple comparison 
expression "a != b" where a's implementation is a NativeString object and b's 
is a plain old java.lang.String.

When ScriptRuntime.eq is called to do the comparison, it calls toPrimitive() on 
the NativeString, which calls getDefaultValue(null) on it.  This resolves to 
the ScriptableObject version of getDefaultValue.  This first tries getting the 
valueOf property and calling it as a function.  If that doesn't work, it tries 
to get the toString properties and call it as a function.

Unfortunately, NativeString doesn't expose either of these as true Function 
properties, so the code in ScriptableObject.getDefaultValue doesn't know what 
to do with the return value and ends up throwing an exception.

My temporary fix was to change NativeString so that it exposes valueOf and 
toString as properties rather than as prototypes.  I'm not entirely sure that 
this is the optimal fix because I don't fully understand how IdScriptable 
works, but this fix got me going again.  The same thing may also need to be 
done to the other "Native" classes.

Here are the diffs for what I did. I'd be interested in feedback on whether 
this is the right approach.

diff -r1.1.1.1 NativeString.java
267a268,275
>         } else {
>             switch (methodId) {
>                 case Id_toString:
>                     return realThis(thisObj, f).jsFunction_toString();
> 
>                 case Id_valueOf:
>                     return realThis(thisObj, f).jsFunction_valueOf();
>             }
830c838,840
<         MAX_INSTANCE_ID              =  1;
---
>         Id_toString                  =  2,
>         Id_valueOf                   =  3,
>         MAX_INSTANCE_ID              =  3;
834c844,846
<         if (s.equals("length")) { return Id_length; }
---
>         if (s.equals("length"))  { return Id_length; }
>         else if (s.equals("valueOf")) { return Id_valueOf; }
>         else if (s.equals("toString")) { return Id_toString; }
908,909c920,921
<         Id_toString                  = MAX_INSTANCE_ID + 2,
<         Id_valueOf                   = MAX_INSTANCE_ID + 3,
---
> //        Id_toString                  = MAX_INSTANCE_ID + 2,
> //        Id_valueOf                   = MAX_INSTANCE_ID + 3,

Comment 1

[Norris Boyd]

I don't understand: the following String and NativeString comparison appears to
do the right thing:

[rhino] java -jar build/rhino1_5R4pre/js.jar
Rhino 1.5 release 4 0000 00 00 (in progress)
js> (new String('hi')) != 'hi'
false

Comment 2

[Laura Werner]

Hmm.  In the case where I ran across this, I have the Rhino interpreter 
embedded in another program.  A Java object that's pretending to be a 
JavaScript one (via NativeJavaObject) returns a NativeString.  Later this gets 
compared to a string literal, ala

  myJavaObject.functionThatReturnsNativeString() != 'foo'

and I get an an exception stack trace like this:

java.lang.RuntimeException: org.mozilla.javascript.PropertyException: 
Constructor for "TypeError" not found.
	at org.mozilla.javascript.NativeGlobal.constructError
(NativeGlobal.java:585)
	at org.mozilla.javascript.NativeGlobal.constructError
(NativeGlobal.java:541)
	at org.mozilla.javascript.NativeGlobal.typeError1(NativeGlobal.java:551)
	at org.mozilla.javascript.ScriptableObject.getDefaultValue
(ScriptableObject.java:619)
	at org.mozilla.javascript.ScriptRuntime.toPrimitive
(ScriptRuntime.java:1540)
	at org.mozilla.javascript.ScriptRuntime.eq(ScriptRuntime.java:1633)
	at org.mozilla.javascript.Interpreter.do_eq(Interpreter.java:2397)
	at org.mozilla.javascript.Interpreter.interpret(Interpreter.java:1577)
	at org.mozilla.javascript.InterpretedScript.call
(InterpretedScript.java:68)
	at org.mozilla.javascript.InterpretedScript.exec
(InterpretedScript.java:59)
	at org.mozilla.javascript.Context.evaluateReader(Context.java:785)
	at org.mozilla.javascript.Context.evaluateString(Context.java:749)
	at bevocal.vxml.ScopeActivation.evalExpr(ScopeActivation.java:793)
	at bevocal.vxml.ScopeActivation.evalExpr(ScopeActivation.java:784)
	at bevocal.vxml.ScopeActivation.evalBoolean(ScopeActivation.java:826)
	at bevocal.vxml.VXMLIf.execute(VXMLIf.java:29)

The stuff at the bottom is mine, and at the top it's trying to construct a 
TypeError object for some reason I don't understand.  But in between you can 
see that it's calling ScriptableObject.getDefaultValue() on the NativeString 
and failing.

I'll try to put together a standalone test case for this in the next couple of 
days.

Comment 3

[Igor Bukanov]

A possible reason for this behavior is that the application did not initialize
NativeString prototype properly to point to String.prototype, where valueOf is
defined. In any case, applications should not use NativeString as it is an
internal class which was public for implementation reasons and it is already
made package private in Rhino CVS.

I suggest to resolve the bug as invalid.

Comment 4

[Phil Schwartau]

OK, I'm going to mark this as invalid, then.
Laura, please reopen the bug if you disagree -

Comment 5

[Phil Schwartau]

Marking Verified -

Comment 6

[Igor Bukanov]

Targeting as resolved against 1.5R4