[Webkit-unassigned] [Bug 66473] New: preventExtensions failing to prevent deleted property bounce back

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=66473

           Summary: preventExtensions failing to prevent deleted property
                    bounce back
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: erights at gmail.com


On WebKit Nightly r93293:

> 'compile' in RegExp.prototype
true
> Object.preventExtensions(RegExp.prototype)
/(?:)/
> delete RegExp.prototype.compile
true
> 'compile' in RegExp.prototype
true


The fact that compile reappears is itself a spec violation. IIUC, at least it is intentional, as it is thought to be required to support some legacy behavior. (Note that this is unlikely to still be true, since RegExp.prototype.compile is deletable on other browsers.)

In any case, since the above delete operation returns 'true', we might try to explain this as triggering some other hidden agent that immediately adds it back in after it gets deleted. With that explanation in mind, If RegExp.prototype has already been made non-extensible, as above, then this attempt to add it back in should fail. As shown above, it doesn't.

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