Although Drupal 8 has had a Conditions Plugin API for a several months, it wasn't until during DrupalCon Austin sprint we managed to get blocks to use the Conditions Plugin API for block visibility.

The great thing about Condition Plugins, is they are re-usable chunks of code, and many contrib projects will be able to take advantage of them (Page Manager, Panels, Rules anyone?)

In this post, I show how you can create an example Page Message module that uses a RequestPath condition plugin to show a message on a configured page.