For the Debian thing, I'm not sure on the specifics for bcachefs-progs (I'm going by what the author is reporting and some blog posts) but I think the problem with Debian is that they willfully ignore when upstream says "this is only compatible with this library version 2.1.x" and will downgrade or upgrade the library into not supported versions, to match the versions used in other programs already packaged. This kind of thing can introduce subtle, hard to debug bugs. It's a mess and problems are usually reported to upstream, that's a recurrent problem for Rust programs packaged in Debian. Rust absolutely isn't this language where if it compiles, it works, no matter how much people think otherwise.

And this is happening even though it's common for Debian to package the same C library multiple times, like, libfuse2 and libfuse3. This could be done for Rust libraries if they wanted to.

Anyway see the discussion and the relevant article here https://news.ycombinator.com/item?id=41407768 and https://jonathancarter.org/2024/08/29/orphaning-bcachefs-too...

But that's exactly the point here. In the context of a whole distribution, you don't want to update some package to a new version (on a stable branch), because that would affect lots of other packages that depended on that one. It may even be that other packages cannot work with the new updated dependency. Even if they can, end users don't want versions to change greatly (again, along a stable branch). Upstreams should accept this reality and ensure they support the older libraries as far as possible. Or they can deny reality and then we get into this situation.

And carrying multiple versions is problematic too as it causes increased burdens for the downstream maintainers.

I'd argue that libfuse is a bit of a special case since the API between 2 & 3 changed substantially, and not all dependencies have moved to version 3 (or can move, since if you move the v3 then you break on other platforms like BSD and macOS that still only support the v2 API).

Rust and especially Golang are both a massive pile of instability because the developers don't seem to understand that long term stable APIs are a benefit. You have to put in a bit of care and attention rather than always chasing the new thing and bundling everything.