[seanmcdirmid]

If File.rm("something") is undoable, then its not a problem right? We are talking about developer tools anyways, its not inconceivable that a mock environment would be setup for the program with undoable side effects or what not. However, this would require serious programming model changes, which are probably not in the scope of Light Table.

[TuringTest]

Which is a shame. As joesb points out above, this severely reduces the benefits of the "instant execution&feedback" features.

Given that this is an alpha release, maybe it's still time to rethink that approach and allow for sandboxed environments.

[ibdknox]

There's absolutely nothing preventing a sandboxed environment :) Connections are just processes that talk over tcp, if the client wants to sandbox whatever it evals, it can definitely do that.

[seanmcdirmid]

Sorry I wasn't clear, but the ability to "undo" an operation definitely requires a programming model change. The sandbox is only one part of that.

Rolling your own magic sandbox isn't going to help much without more buy in from the environment (though, I'm sure most of us test in sandboxes anyways).