1103344 - Remove the try/catch behavior of Object.assign

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, defect)

Description

[ziyunfei]

js> obj=Object("0")
(new String("0"))
js> Object.assign(obj, {0:1, 1: 1})
typein:2:0 TypeError: 0 is read-only
js> obj[1]
1 // this should be undefined

TC39 decided to remove this for performance reasons: https://twitter.com/bterlson/status/535921786525736960

Comment 1

[Tom S [:evilpie]]

Attachment: Object.assign should stop when an exception is thrown

Comment 2

[Till Schneidereit [:till]]

Comment on attachment 8580752 [details] [diff] [review]
Object.assign should stop when an exception is thrown

Review of attachment 8580752 [details] [diff] [review]:
-----------------------------------------------------------------

Mmmmmh, so much nicer!

::: js/src/builtin/Object.js
@@ +30,4 @@
>  
> +            // Steps 5.c.i-iii. We abbreviate this by calling propertyIsEnumerable
> +            // which is faster and returns false for not defined properties.
> +            if (callFunction(std_Object_propertyIsEnumerable, from, nextKey)) {

It'd be really nice to inline std_Object_propertyIsEnumerable to substantially speed this up. Perhaps file a bug so it's at least visible?

Comment 3

[Tom S [:evilpie]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=3e4f8caef1dc
https://hg.mozilla.org/integration/mozilla-inbound/rev/c279eefced07

Filed bug 1147154 for inlining propertyIsEnumerable. That was quick, even before coming back from your vacation! :)

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/c279eefced07

Comment 5

[Florian Scholz (Open Web Docs)]

https://developer.mozilla.org/en-US/Firefox/Releases/39#JavaScript
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign