Stub local and session storage in JSDOM

[ryanhamley]

Launch Checklist

This replaces #7455

JSDOM 11.12 introduced the localStorage API. Our codebase copies properties from one JSDOM instance to another which worked fine but when accessing localStorage in a Node context where the JSDOM's base URL is not set, an error is thrown. localStorage is not used in our tests (we stub it out in a couple of places) so I think this is probably an acceptable workaround. Setting the JSDOM's base URL can cause issues with some tests and creates potential CORS errors that makes testing a pain.

Tip of the 🎩 to @fc for reporting the original bug and helping figure out what exactly was going wrong.

[fc]

Would it be desirable to upgrade JSDom along with this?

[asheemmamoowala]

@ryanhamley Would a stub implementation with an exception be better than deleting the properties? It would help debug if new code relied on either of these.

[ryanhamley]

I've updated package.json so JSDOM can freely upgrade and stubbed out [local/session]Storage with a warning log in case anyone attempts to access either property. Edit for posterity: The properties have to be deleted before they can be stubbed because they only have getter methods and cannot be directly overridden.