Customize: Defer triggering selective refresh for all settings until after synced

[westonruter]

Selective refresh is triggered when a setting is added, changed, or removed. In the case of being added, there are scenarios where infinite full refresh can ensue if a partial has fallback refresh. This has been particularly evident for nav menus. While the infinite refreshes have largely been fixed for nav menus in #38612, there are still cases more generally where settings could be registered in the controls (admin) but not in the preview (pane). In the case of nav menus, this still causes a selective refresh to happen even at an initial page load.

This is essentially revisiting #37032.

[westonruter]

Something that I still want to address is the scenario where a user may make a change to a postMessage-transport setting while a full refresh is happening. In that case, we *do* want there to be an initial selective refresh happening.

[westonruter]

Easiest way to reproduce this issue is to activate the Nav Menu Roles plugin and prevent a few menu items from being displayed when a user is logged in. When loading the customizer preview, the menu containing these excluded items will get initially selective-refreshed.

[celloexpressions]

+1, if we can eliminate the initial selective refresh for menus, even, this would be a big improvement. If the changes aren't too much more complex after addressing 1, I think it's worth getting this into the 4.7 branch.

[westonruter]

I noticed infinite refresh happening in Twenty Fifteen in 4.8 when deleting a menu assigned to a nav menu location.

[westonruter]

I've not been noticing this and I haven't heard it reported. Punting.

[pento]

Patch needs testing and a decision.

[westonruter]

New feature development is being directed toward the Site Editor, so I'm closing this.