[hyperpallium]

Dependency injection? The conditionals are then virtual (which implementation of an interface); the same controls apply to front-end code; global dependency configuration.Though all that infrastructure and boilerplate for explicit modularity is probably only worthwhile at Facebook-scale.

With each feature in a separate file, there is no merging of features, and if you squint your eyes you can see each possible dependency configuration as a git branch, selecting certain files out of a repository, just at runtime. There are no file-level merges, only different files, and different configuration selections. (Of course, modifying code to use the interface in the first place is a file-level change.)

BTW I've been thinking about this problem in the context of computational fluid dynamics, where you want to try different scales, fluid and container initial condition profiles and boundary conditions, as well as different discretizations, schemes and variations thereof. Basically, experimental cases (a bit like "functional test" setups).