Support User: Bypass localForage while active to avoid conflicts across sessions

[jordwest]

Bypasses localForage while support user is active. This allows sync-handler and other persistent data stores using localForage to use a 'sandboxed' temporary in-memory store while support user is active, avoiding conflicts with the original user's persisted data. This doesn't cover instances of direct localStorage usage - see #3941 which covers that.

The goal is to eventually move all direct localStorage usage to localForage.

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This still needs some more testing, but overall it's working.

localforage-bypass.js was copied and modified from a localForage testing module; we can likely cut quite a bit of cruft out of it as a lot of the logic relates to test facilitation. (cruft removed in 4c39e79)

Things to test:

• With support-user feature flag disabled
• With wpcom_user_bootstrap enabled
• Running in non-development environment
• Running in development
• Chrome 49
• Firefox
• Safari
• IE

cc @retrofox @gwwar

[jordwest]

@gwwar After a lot of trial and error, what we chatted about earlier worked 😃 Would you mind taking a look at this solution? Basically to solve the issues with the fact that localForage.defineDriver is async:

• The build-env.*.js and other Calypso specific bundles are not loaded on boot. Instead we make sure support user has done any pre-boot async tasks (in this case running localForage.defineDriver) before loading the Calypso bundle. This only happens when the query string is set:
• A ?support_user=true query string is passed to inform the server that this will be a support user session. This allows the server to leave out any user specific info including the user bootstrap and to inject a special pre-boot sequence.
• localforage package was added to the vendor bundle so that the same instance is shared by both the support user pre-boot bundle and the main Calypso bundles.

After this change, it should even be possible to remove some of the changes introduced in #3879, as the Redux store would no longer need to know about the support user state. Instead, because initialReduxState is undefined and any attempts to save/load from localForage will be bypassed, the Redux store should function as expected without being aware that it's sandboxed.

[gwwar]

const

[gwwar]

👍 Nice approach. I'll clean up #3879 after this lands. I verified that we write to a dummy driver when we switch users.

We may want some more 👀 for the bundle updates. Maybe @mtias or @aduth?

[jordwest]

Thanks for the review @gwwar. I've cleaned up localforage-bypass.js and added unit tests. The PR is getting quite large now, so I've split out the new pre-boot sequence to a separate PR: #4068. Once that lands this one should reduce in size.

[aduth]

Does this need to be nested?

[jordwest]

This now uses the changes that landed in #4114 to bypass localForage on startup. Here's an overview of how we overcame the async issue described above:

[gwwar]

Edit: my bad, failed to switch over to the other branch properly

[jordwest]

Hmm, that's weird, are you seeing a Cannot bypass localforage after initialization error in the console?

[jordwest]

Oh 😄

[gwwar]

[jordwest]