More [[DefineOwnProperty]]
-----Original Message----- From: es-discuss-bounces at mozilla.org [mailto:es-discuss- bounces at mozilla.org] On Behalf Of Jeff Walden Sent: Monday, June 08, 2009 6:14 PM To: es-discuss at mozilla.org Subject: More [[DefineOwnProperty]]
In Array's [[DefineOwnProperty]], what is the rationale for calling the default [[DefineOwnProperty]] with a Throw argument specified as false, rather than the Throw provided to the initial call?
False is passed because this call will always succeed if all the other invariants of the specification are maintained.
Arguably a clarifying note might be a good idea or Throw could be passed with on net change to the semantics.
In step 6, does "same value" mean the SameValue spec operation? If so the expected notation should be used here.
Yes, SameValue is the intent and yes it should be written that way in the spec.
Since no property is guaranteed to be present, by the time we reach step 7, we cannot rely on every property of Desc being present. How then should 7a be interpreted if [[Configurable]] was missing from Desc,
If [[Configurable]] is missing then it certainly is not true.
or 7b if [[Enumerable]] is missing from Desc,
If [[Configurable]] is missing then it can not be the Boolean negation of the [[Configurable]] field of current.
or 10a(i) if [[Writable]] is absent from Desc?
If [[Writable]] is missing then it is not true.
The specification incorrectly assumes each is
actually present in the property descriptor.
No, but since it appears to be a source of confusion it may be worthwhile clarify the language of the specification in this regard.
I believe these last concerns only further demonstrate why standalone [[Configurable]]/[[Enumerable]]/[[Writable]] modifications should be removed to their own method rather than leaving them in Object.defineProperty, as I requested in a previous thread.
The conclusion is based upon a false premise. Regardless, it would be take a much broader base of concern to substantially change the Object reflection API at this point in the release process of ES5.
In Array's [[DefineOwnProperty]], what is the rationale for calling the default [[DefineOwnProperty]] with a Throw argument specified as false, rather than the Throw provided to the initial call?
In step 6, does "same value" mean the SameValue spec operation? If so the expected notation should be used here.
Since no property is guaranteed to be present, by the time we reach step 7, we cannot rely on every property of Desc being present. How then should 7a be interpreted if [[Configurable]] was missing from Desc, or 7b if [[Enumerable]] is missing from Desc, or 10a(i) if [[Writable]] is absent from Desc? The specification incorrectly assumes each is actually present in the property descriptor.
I believe these last concerns only further demonstrate why standalone [[Configurable]]/[[Enumerable]]/[[Writable]] modifications should be removed to their own method rather than leaving them in Object.defineProperty, as I requested in a previous thread.