Async importScripts() in SW is problematic

[jeffposnick]

As per the SW spec, and summarized at w3c/ServiceWorker#1319 (comment), calls to importScripts() are allowed either during the initial, synchronous, top-level SW execution or during the install event handler.

Chrome doesn't currently follow the spec and allows arbitrary, async importScripts(), but this is a bug that needs to be fixed.

Using this library could lead to folks to inadvertently calls importScripts() in a way that is meant to be disallowed, and (if they only test on Chrome) erroneously thinking that everything works fine because Chrome isn't throwing an exception.

[surma]

Hm...

Good that you file this. I’ll leave it like this for now as the only alternative would be fetch() + eval(), which is not CSP compliant. I’ll add a note to the README.

[surma]

On second thought, I’ll leave this open and think a bit more on what the right course of action is

[surma]

Fixed in 8cb54b7 by providing an option.