1007334 - ES6 Proxies: There's no such thing as [[GetOwnPropertyNames]]

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, defect)

Description

[Eric Faust [:efaust]]

The ES6 spec demands that Object.getOwnPropertyNames calls [[OwnPropertyKeys]] and then does some work on it. Currently, we have a getOwnPropertyNames trap, which will erroneously call a method on the handler with that name.

Comment 1

[Eric Faust [:efaust]]

Attachment: Clean up the GetOwnPropertyNames/Keys situation for scripted proxies

Comment 2

[Jason Orendorff [:jorendorff]]

Comment on attachment 8421202 [details] [diff] [review]
Clean up the GetOwnPropertyNames/Keys situation for scripted proxies

Review of attachment 8421202 [details] [diff] [review]:
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Great!

Besides these tests, at least browser/extensions/shumway/content/shumway.js also needs to be changed. (Ask till if he wants to keep the old method around too, for compatibility with older Firefoxen.)

Definitely add a test checking that the getOwnPropertyDescriptor trap is called for each property during Object.keys().

::: js/src/jsproxy.cpp
@@ +1076,5 @@
>                       MutableHandleValue vp) MOZ_OVERRIDE;
>      virtual bool set(JSContext *cx, HandleObject proxy, HandleObject receiver, HandleId id,
>                       bool strict, MutableHandleValue vp) MOZ_OVERRIDE;
> +    // Kick keys out to getOwnPropertyName and then filter. [[GetOwnProperty]] could potentially
> +    // change the enumerability of the target's properties.

getOwnPropertyName is missing its s in the first sentence.

In the second sentence, mentioning changing enumerability is making it more abstruse than it really is. The question is which traps are called when you do Object.keys(proxy): standard behavior that scripts can trivially observe.

I'd write:

    // The DirectProxyHandler implementation of keys() is observably different from
    // what the spec requires (see tests/ecma_6/Proxy/blahblah.js), so use the base
    // class implementation (call getOwnPropertyNames and then filter).

@@ +1663,5 @@
>      return true;
>  }
>  
> +// This is secretly [[OwnPropertyKeys]]. SM uses the old wiki name, internally.
> +// ES6 (5 April 2014) Proxy.[[OwnPropertyKeys]](O)

Follow-up bug. Let's rename everywhere.

Comment 3

[Jason Orendorff [:jorendorff]]

Can this land?

Comment 4

[Eric Faust [:efaust]]

> Can this land?

https://hg.mozilla.org/integration/mozilla-inbound/rev/cdb97e86cc74

> Follow-up bug. Let's rename everywhere.

I didn't file it, but it's filed as bug 1026918

Comment 5

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/cdb97e86cc74
https://hg.mozilla.org/mozilla-central/rev/799a2838ed86
https://hg.mozilla.org/mozilla-central/rev/74fd773a5319

Comment 6

[David Bruant]

If this bug is only about the renaming of "getOwnPropertyNames" and "keys" traps to "ownKeys", then I declare dev-doc-complete.
Thanks Yoric, evilpie and jorendorff!
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy$compare?to=641711&from=632073
(diff is hard to read, but at least it shows the 2 revisions between which the related changes happened)