12010 - Rhino: instanceof does not appear to work properly with Date

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P3)

Description

[david_gennaco]

The function
   function CheckDate(d)
   {
      return (d instanceof Date);
   }
returns false when called with the returned value of the following function
   function GetDate()
   {
      return new Date();
   }
(I use call to execute the function and then use the Java Object returned
   to make the CheckDate call)

I traced a debug version of the Rhino API and found this in the underlying
code at the end (the Object.equals() method causes the return to be false):

Thread-6[1] step
Thread-6[1]
Step completed: thread="Thread-6", org.mozilla.javascript.ScriptRuntime.jsDelega
tesTo(), line=1725, bci=0
  1725  Scriptable proto = lhs.getPrototype();

1721            *
1722            * @return true iff rhs appears in lhs' proto chain
1723            */
1724           protected static boolean jsDelegatesTo(Scriptable lhs, Scriptable
 rhs) {
1725    =>      Scriptable proto = lhs.getPrototype();
1726
1727            while (proto != null) {
1728                if (proto.equals(rhs)) return true;
1729                proto = proto.getPrototype();
1730            }
Thread-6[1] Thread-6[1] eval lhs.getPrototype()
lhs.getPrototype() = instance of org.mozilla.javascript.NativeDate(id=1001)

Thread-6[1] eval rhs
rhs = instance of org.mozilla.javascript.NativeDate(id=1000)
Thread-6[1]

Comment 1

[Mike McCabe]

Reassigning to Roger.

It's my code, but you'll likely be touching it soon :)

Comment 2

[rogerl (gone)]

Taken as is, I can't find a problem, the script:

function CheckDate(d) { return (d instanceof Date); }
function GetDate() { return new Date(); }
CheckDate(GetDate());

returns 'true'. I suspect there's more going on than thi,s though?  Can you
provide a test case or describe the runtime environment more?

Comment 3

[rogerl (gone)]

Bug turned out to be the result of the embedding re-initializing the standard
objects before each function invocation.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/74f554464a22
[fenix] For https://github.com/mozilla-mobile/fenix/issues/12010: Follow ux mock on Settings --> ETP --> Info screen (https://github.com/mozilla-mobile/fenix/pull/12429)