[Webkit-unassigned] [Bug 134346] New: iOS 8 beta 2 ES6 'Set' clear() broken

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=134346

           Summary: iOS 8 beta 2 ES6 'Set' clear() broken
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: iOS
               URL: http://www.scirra.com/labs/bugs/testset.html
        OS/Version: Other
            Status: NEW
          Severity: Major
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: ashley at scirra.com


Visit the test URL above. In iOS 8 beta 2, 'Set' is present, but broken. Note the last test logs "FAIL: Set does not contain item3". This means after a call to clear(), the size is 0 but it still returns true when calling has() on one of the items.

Reproduces on iOS 8 in both Safari and the web view. Does not reproduce on Firefox desktop or Firefox Android, IE11, or Chrome with experimental Javascript enabled.

Rating this as 'Major' because the Construct 2 HTML5 game engine (www.scirra.com) already has thousands of games deployed over the web which feature-detect 'Set' and if present, uses it for various internal engine structures; if it is not present, it uses a shim based around setting and deleting object properties. We can work around this in our engine, but the bug has catastrophic consequences for large amounts of existing web content using the Construct 2 engine, since it relies heavily on Sets in crucial parts of the engine to the extent that the broken Set ruins gameplay (objects not destroyed, sounds stuck playing in loops, other unpredictable consequences). Therefore 'Set' either needs to be fixed or removed entirely to prevent breaking lots of games.

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