is_admin_bar_showing() is true in REST API requests

[Rarst]

is_admin_bar_showing() returns true if logged in and looking at REST API request.

This is inconsistent with it being explicitly false for XML RPC and Ajax requests.

[SergeyBiryukov]

It already checks for XMLRPC_REQUEST, DOING_AJAX, and IFRAME_REQUEST.

Just need to add a check for REST_REQUEST, by the looks of it.

[Rarst]

I remember having issues with REST_REQUEST being defined relatively late, so it's not as reliable as DOING_AJAX (which is hardcoded right on top of its endpoint). Timing needs to be checked out there against what the check is doing.

[SergeyBiryukov]

Right, REST_REQUEST is not defined until parse_request runs.

wp_is_json_request() should be used then, see [43730] for #44534.

[ayeshrajans]

Attaching a patch inspired by changeset 43730.

[pento]

In 44608:

Admin Bar: Set the Admin Bar to not be showing on REST API requests.

Props ayeshrajans.
Fixes #45727.