Blocking such changes might be an entirely reasonable thing to do. I've seen it a number of times. CL author implements some feature, touching a library in the

Blocking such changes might be an entirely reasonable thing to do. I've seen it a number of times. CL author implements some feature, touching a library in the process. The changes made to the library help them match their requirements but are awfully specific to whatever feature it is they're implementing and don't make much sense in the context of the existing library API. Sorry, but NAK. Don't increase the API surface with one-off additions just because it is the most convenient way to implement some feature. If you can't do with the existing API and don't think there's a nice and general abstraction to add to the library, you might want to figure out the absolute minimum API modification necessary that lets you achieve what you want to do. It might require more effort in the user part of the code, but is also that much more likely to be acceptable.