My opinion, as someone whose code got broken by a library micro version update just yesterday, is that the responsible thing to do is add a new function with the new args instead of changing the old one. Change the implementation of the old one so it calls through to the new one with suitable parameter values & and mark the old version as deprecated, but please don't remove it until the next major release!
That's what I do in most cases. But sometimes there's just no option.
The particular case that I was referring to when I said I decided to put off changes because I didn't want to bump the version number was actually a stylistic change, renaming a method from `parse(with:)` to `parse(using:)`, in order to better match the Swift 3 naming conventions. Normally I would have just marked the old method as deprecated, except a compiler bug means that if I do so, any code using trailing-closure syntax fails to compile (https://bugs.swift.org/browse/SR-3227). So it's literally impossible for me to rename this method in this manner without deleting the old method entirely (which is a breaking change). But I just bumped the major version number recently when Swift 3 was released, and I didn't want to bump it again shortly afterwards just because I didn't consider this method name during the Swift 2->3 migration.
Fair enough, I understand the desire not to bump the major version in this case. It does still kind of suck for users of the library though.
The case I was talking about was the OpenVR library, which changed the names for some of its enum values in the upgrade from 1.0.4 to 1.0.5. The change was documented in the release notes and it was straightforward to fix our code, but now we have to document that we require at least v1.0.5 and everyone building our code has to update their copy of OpenVR and so on. There are knock-on effects, is what I'm trying to say.
