Fix Javascript numeric properties type detection

[riprwwa]

When calling C# code from Javascript one can send objects as parameters.
These objects get translated to C# as System.Dynamic.ExpandoObject instances.
The types of these properties are inferred by the SerializeV8Object method in CefSharp.BrowserSubprocess.Core\Serialization\V8Serialization.cpp.

If setting a numeric property's value to something that fits into 32 bits, the property's type is inferred to be System.Int32.
If the value is greater than 2147483647 (which is 2^31-1) then the value is mistakenly interpreted to be a negative number:

• 2147483647 is correctly seen as 2147483647
• 2147483648 is incorrectly seen as -2147483648
• 2147483649 is incorrectly seen as -2147483647 and so on

One can easily test this by evaluating the following code in the CefSharp.Wpf.Example project, under "Evaluate Javascript (Async)"
(() => { var a = { s: 2147483648 }; return a.s; })()
and see that the result is a negative number.

@amaitland has suggested a workaround in a discussion in Gitter:

[...]
else if (obj->IsInt())
{
    //CEF Doesn't differentiate between UINT and INT
    //so we have to do some additional bounds checking
    //To make sure the correct value is returned
    auto uIntVal = obj->GetUIntValue();
    if (uIntVal > INT_MAX)
    {
        //We have to use double as there is no IPC support
        //for UInt
        list->SetDouble(index, obj->GetDoubleValue());
    }
    else
    {
        list->SetInt(index, obj->GetIntValue());
    }
}
[...]

which does the trick in both the code I posted above, and my team's specific case.
Seeing as Javascript always treats numbers as double anyway, is there a reason not to apply the suggested fix?

I can create a pull request if need be, just wondering if/what I'm missing.

Thanks!

[amaitland]

Thanks for following up.

Seeing as Javascript always treats numbers as double anyway, is there a reason not to apply the suggested fix?

It's simply a matter of testing. An xUnit test will need to be added to validate the behaviour.