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Re: [WebIDL] platform array objects

From: Cameron McCormack <cam@mcc.id.au>
Date: Fri, 19 Aug 2011 15:00:19 +1200
Message-ID: <4E4DD1C3.2080004@mcc.id.au>
To: andrew@ado.is-a-geek.net
CC: public-script-coord <public-script-coord@w3.org>
Thanks for your comments Andrew.

Andrew Oakley:
> http://dev.w3.org/2006/webapi/WebIDL/#es-array:
>> Platform array objects defy being fixed; if Object.freeze,
>> Object.seal or Object.preventExtensions is called on one, the
>> function MUST throw a TypeError.
>
> Can I ask why? I don't see any reason for this and it feels like it
> would make implementations more complicated. (This also seems to be
> present in the platform objects description.)

I think it makes implementations simpler -- then there is no need to 
define and handle what should happen to properties on a platform array 
object if it changes length.

> § 4.2.20.1 Platform array object [[GetOwnProperty]] method says that the
> property descriptor for "length" whould have [[Configurable]] set to
> true. Later on we try to make sure it can't be deleted (§ 4.2.20.3).
> Would it not be easier just to make it not [[Configurable]]?

To be able to implement platform array objects with proxies, we need to 
expose configurable properties, since last I checked the Proxy proposal 
did not support exposing non-configurable properties.  If this has 
changed, then I agree we should make it non-configurable.

> The [[GetOwnProperty]] implementation also tries calling the normal
> version of [[GetOwnProperty]] at the end of the algorithm rather than at
> the start like Array and Arguments objects. I could agree with it being
> either way round, but it would be nice to be consistent with the
> ECMAScript spec.

Array objects don't have a specialised [[GetOwnProperty]] do they? 
Anyway for platform array objects, I don't think it matters too much, 
since there can never be a "real" own property named "length" or like 
one of the array index properties on an platform array object.

I think it looks cleaner as is, resolving the special properties first 
before looking at the regular properties, so I will leave it.

> Finally, we don't define what "Reject" means here (although we do define
> it for the "platform object" algorithms.

Good point, I've added some wording before the platform array object 
algorithms that use it.


http://dev.w3.org/cvsweb/2006/webapi/WebIDL/Overview.html.diff?r1=1.341;r2=1.342;f=h

If the above resolutions are satisfactory, could you please indicate so 
for the Disposition of Comments document I will need to assemble for 
this Last Call.

Thanks,

Cameron
Received on Friday, 19 August 2011 03:01:05 UTC

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