591838 - Object.defineProperty is using === rather than SameValue

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, defect)

Description

[Mark S. Miller]

> Object.getOwnPropertyDescriptor(window, 'NaN').toSource()
  ({value:NaN, writable:false, enumerable:false, configurable:false})

  > Object.defineProperty(window, 'NaN', {value: NaN})
  TypeError: can't redefine non-configurable property 'NaN'

By SameValue, this is an allowed harmless setting of the property to its current state. But if Object.defineProperty is using === instead, it would think we're trying to make a forbidden change.


on Mozilla/5.0 (Macintosh; Intel Mac OS X 10.5; rv:2.0b5pre) Gecko/20100827 Minefield/4.0b5pre

Comment 1

[Jeff Walden [:Waldo]]

This isn't the absence of use of SameValue, because the analog works fine in the shell: I suspect a browser-global-window-specific quirk.

Comment 2

[Mark S. Miller]

Thanks for the quick response. Yes, the bug does not occur for non-window objects. Also, the bug does also occur on window for 'Infinity' and 'undefined'.

Comment 3

[Mark S. Miller]

And only when using the names 'NaN', 'Infinity', and 'undefined'. Doing redundant defineProperty on window with these values by any other name smells much sweeter.

Comment 4

[Mark S. Miller]

Shouldn't this be closed as invalid?

Comment 5

[Mark S. Miller]

Should this bug be closed?

Comment 6

[Jeff Walden [:Waldo]]

It seems like a valid bug to me.  I doubt WebIDL or something or other would end up making this not work somehow (a [[DefineProperty]] hook on window objects defined just so in order to produce this behavior?).  In the absence of any other direction this seems like a valid bug to me, just reasonably low priority as you basically have to try to trigger it in order to be surprised, and the only thing you'd expect the try to get you would be a no-op, so there's no point in trying anyway.

Comment 7

[Mark S. Miller]

I cannot reproduce the reported buggy behavior on FF4.0.1. Am I missing something?