Ever since Firefox 2 we have vaguely supported a form of extension dependency. That is marking an extension as requiring particular versions of another extension.
The support is currently very limited and when a user tries to use an add-on that depends on something they don’t have they are pretty much left in the cold. While we tell them it requires something we don’t tell that what it requires or give them any easy way to download and install it.
Given this poor implementation it is perhaps no surprise that very few extensions make use of the feature (something like 50 listed on AMO, many of which are outdated). This raises questions over the cost of continuing to support this feature particularly now when we are undergoing large scale changes to the add-ons manager architecture to give better support to personas and jetpacks.
Before I made any final decisions I wanted to gather some feedback on what people thought about completely dropping the support for dependencies for now. We will always have the option to add it back again (even in a more functional state) at a later time should we decide it is worthwhile. Unfortunately it’s certainly not on the cards right now to complete the implementation as it stands and even leaving it as it is is costing significant work during the refactoring project.
Extensions can always handle dependencies themselves at runtime by testing for the presence of whatever they depend on. They can even then give the user a way to get what they need which makes for a far better user experience than the platform currently offers so I’m not sure I see a convincing reason to keep the feature as it is around for now.