Many libraries support configuration code, translations, HTML themes or other content in files of a specific format. The Doctrine ORM, for example, is able to load entity mappings from special XML files. When setting up Doctrine, we need to pass the location of the *.dcm.xml file to Doctrine’s XmlDriver. That’s easy as long as we do it ourselves, but what if someone else uses our package? How will they find our file? What if multiple packages provide *.dcm.xml files? How do we find all these files? We need to remove the appropriate setup code after removing a package [and] we need to adapt the setup code after installing a new package. Multiply this effort for every other library that uses user-provided files and you end up with a lot of configuration effort. Let’s see how Puli helps us to fix this.
He talks about the concept of package roles in the tool, breaking them down in resources and providers. He then shows how Puli makes it possible to discover resources by defining a type via Puli and the code for the discovery process. He then binds the XML configuration definition and executes a "find" to ensure it's configured correctly. Finally, he shows the process to use Puli in this Doctrine example allowing it to locate and use the XML mappings dynamically via a custom driver.