I’ve been working on a write-up for the 2020 State of Clojure survey (sorry that’s taking so long). One feedback comment stuck with me:

“A lot of libraries in the Clojure ecosystem (including in clojure.core) have version 0.y.z, indicating breaking changes could still be introduced. Yet some of these libraries have widespread adoption. The Clojure community emphasises the importance of backwards compatibility, but including some-lib 0.y.z in a large production system still makes me uncomfortable. What is preventing these libs, like data.csv, from becoming stable?”

The short answer to this is a) nothing and b) these libraries have already been stable for years.

The Clojure ecosystem in general is not big on the concept of semantic versioning (see Rich’s talk about why semver is broken), and I personally do not see 0.x vs 1.x as having any special meaning. But clearly that is not the case for the commenter above, or for other comments I’ve seen of the same vibe. I suspect this is probably most strongly the case for those coming from the JavaScript/NPM ecosystem, or other language communities where semver is held in higher regard.

Semver tries to separate “major” changes (anything could have changed, and you may be broken by updating) from “minor” changes (additive or fixative changes and you will not be broken by updating). Rich’s point is that breaking APIs is not the way to build a stable software ecosystem, and we should stop doing it. Also, you can turn a breaking change into a growing change by giving it a new name, rather than changing the meaning of the old name. If you pursue growth over breakage, then there is never a version that “breaks” users. tools.deps has its own version selection algorithm that aligns with this (always preferring newer over older versions).

Clojure and the contrib libraries have endeavored to follow this model of change for a long time. Consequently, we have lots of libraries in the Clojure ecosystem that have been around for many years, are widely used, have stable APIs, and yet are 0.x version. It’s silly for that to be (falsely) indicating to people not to use them, so I have asked Clojure contrib library owners to more actively bump up their library versions.

If you are a Clojure library maintainer and in this same position, I’d encourage you to bump as well!