Back when EAPI 6 was approved and ready for deployment, I have written a blog post entitled the Ultimate Guide to EAPI 6. Now that EAPI 7 is ready, it is time to publish a similar guide to it.
Of all EAPIs approved so far, EAPI 7 brings the largest number of changes. It follows the path established by EAPI 6. It focuses on integrating features that are either commonly used or that can not be properly implemented in eclasses, and removing those that are either deemed unnecessary or too complex to support. However, the circumstances of its creation are entirely different.
EAPI 6 was more like a minor release. It was formed around the time when Portage development has been practically stalled. It aimed to collect some old requests into an EAPI that would be easy to implement by people with little knowledge of Portage codebase. Therefore, the majority of features oscillated around bash parts of the package manager.
EAPI 7 is closer to a proper major release. It included some explicit planning ahead of specification, and the specification has been mostly completed even before the implementation work started. We did not initially skip features that were hard to implement, even though the hardest of them were eventually postponed.
I will attempt to explain all the changes in EAPI 7 in this guide, including the rationale and ebuild code examples.