[Webkit-unassigned] [Bug 172683] Debugger has unexpected effect on program correctness

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=172683

--- Comment #2 from Joseph Pecoraro <joepeck at webkit.org> ---
I think its reasonable to assume that having Web Inspector open should have as little impact on the page as possible, to avoid altering execution behavior of programs.

Adding a console.trace() to the Array.prototype[@@iterator] accessor we see:

    [Log] Trace
        get (test-case.html:15)
        _appendPropertyPreviews
        _generatePreview
        RemoteObject
        _wrapObject
        CallFrameProxy
        wrapCallFrames
        Global Code (test-case.html:21)

    [Log] Trace
        get (test-case.html:15)
        Set
        _isPreviewableObject
        _appendPropertyPreviews
        _generatePreview
        RemoteObject
        _wrapObject
        CallFrameProxy
        wrapCallFrames
        Global Code (test-case.html:21)

So this is Web Inspector using `for..of` inside the page with the InjectedScriptSource. This happens when generating information in the debugger, for data in the Scope Chain details sidebar and Object previews.

In order to avoid this we would need to eliminate observable operations (like for..of) in InjectedScriptSource. A big step in that direction (eliminating observable behavior) is moving it to be a built-in:
<https://webkit.org/b/152294> Web Inspector: Parse InjectedScriptSource as a built-in to get guaranteed non-user-overriden built-ins

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