In his latest post Matthias Noback suggests the idea that there's no such thing as an optional dependency when it comes to working with packages and Composer.
On several occasions I have tried to explain my opinion about “optional dependencies” (also known as “suggested dependencies” or “dev requirements”) and I’m doing it again: "There’s no such thing as an optional dependency." I’m talking about PHP packages here and specifically those defined by a composer.json file.
So that everyone's on the same page, he starts with an example of a true dependency in a sample adapter class. He asks the usual question - "what's needed to run this code?" - and looking a bit deeper at the "suggested" packages. As it turns out, some of these dependencies turn into actual requirements when you need certain features of the tool. He points out that this is a problem with quite a few packages in the Composer ecosystem and proposes a solution - splitting packages based on requirements. He gives an example based on his adapter with a Mongo requirement split off into a "knplabs/gaufrette-mongo-gridfs" package that's more descriptive of the requirements.