930523 - createObjectIn should waive before returning

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Bobby Holley (:bholley)]

Gabor and I discussed this during our meeting today. Our eventual conclusion was that there's not really any point to forcing consumers to use .wrappedJSObject to add properties to an object that they've created. The two things you might want to do with an object created by createObjectIn are:

(1) Define properties on it.
(2) Export functions using exportFunction.

(1) only works with a waiver, and does nothing useful without it. (2) is agnostic  to the existence of a waiver.

In particular, consumers are unlikely to be pulling content-side properties off these objects, which is the main hazard of adding waivers where they didn't previously exist (since the waivers might leak into objects that the consumer didn't expect). So I think we're good to do this.

Comment 1

[Gabor Krizsanits (INACTIVE)]

Attachment: createObjectIn should waive. v1

Comment 2

[Bobby Holley (:bholley)]

Comment on attachment 825343 [details] [diff] [review]
createObjectIn should waive. v1

Review of attachment 825343 [details] [diff] [review]:
-----------------------------------------------------------------

Make sure to run this through try if you haven't already. Also, please document this in the IDL and on MDN:

https://developer.mozilla.org/en-US/docs/Components.utils.createObjectIn

::: js/xpconnect/tests/chrome/test_APIExposer.xul
@@ +25,5 @@
>        sandbox.is = is;
>        Cu.evalInSandbox("Object.defineProperty(Object.prototype, 'getProp', { get: function() { throw 'FAIL: called getter' }, set: function() { throw 'FAIL: called setter'; } })", sandbox);
>  
>        var obj = Cu.createObjectIn(sandbox);
> +      is(Object.getPrototypeOf(obj), Cu.waiveXrays(Cu.evalInSandbox("Object.prototype", sandbox)),

Please also check |obj == Cu.waiveXrays(obj)|

Comment 3

[Gabor Krizsanits (INACTIVE)]

remote:   https://hg.mozilla.org/integration/mozilla-inbound/rev/9b23ec089b24

https://tbpl.mozilla.org/?tree=Try&rev=5b4c09cc96d2

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/9b23ec089b24