This Pull Request is a "take over" of #2144.

Description of the Change

As described in #2121, in multisite environment and searching the whole network when the_post is triggered outside the loop, the current site is not restored if the first result is from another blog. To fix the issue I'm checking if the WP_Query instance is in the loop and if not, calling restore_current_blog(). To do this properly I had to add second argument to ElasticPress\Indexable\Post\QueryIntegration->maybe_switch_to_blog().

Alternate Designs

In the project where I first discovered the issue I added another function to the_post to restore the current blog, but that is not necessary if the issue can be addressed at it's roots.

Benefits

Fix the issue, described in #2121. The original PR content:

Possible Drawbacks

I can't find any.

Verification Process

I tested that the issue dissappears in my test setup and made sure current tests are passing.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Issue #2121.

Changelog Entry

Fix: Restore current blog when the_post triggers outside the loop in multisite environment and the whole network is searched if the first result is from another blog. Props @gonzomir