Garbled

Ben’s Gem Maintainer Handbook

At work, recently, we were discussing internal gems and how to deal with releases and crap. Of course, because this is a topic, I have opinions on it. I can’t help myself.

Actually, someone was like, “Why do we do it this way,” and someone else was like, “I don’t know, ask Ben,” and I was all, “Ranty rant-ra–You know what? I’ll just write a blog post.” So, now you’re all inflicted with this. You have Bob and Ryan to thank for it.

SemVer

So this is pretty simple, and other people have explained it better than I can. You should be using Semantic Versioning for your gem. You can read the full spec, but I’ll break down the general idea real quick.

Version numbers are 3 segments in the format major.minor.patch. You increment the major version if you’re shipping any backwards-incompatible changes. You increment the minor version if you’re adding backwards-compatible new features. You increment the patch version if you’re just doing bug fixes. When you increment one segment, all the segments to the right reset to 0.

This way, a consumer of your gem can tell by looking at the difference in version number whether the changes should be backwards compatible or not (major version changed) or whether that new exciting feature they’ve been waiting for might be in (minor version changes).

Version Number

If I’m in a REPL with your gem loaded, I should be able to ask it what it’s version number is, so put the version number in the code. Ideally, I think, it should be a string of the numbers. Some people seem to like to have MyGem::VERSION be how you get it. Personally, I like to provide MyGem.version, as well.

If you do this, you can then refer to it in your gemspec, where you officially set the version of the gem. You should put it alone in it’s own file, though, so you don’t have to load your whole gem just to interleave your version number into the gemspec.

CHANGES.md

Keep a changes file. There are a few file names that seem to be widely recognized, but I like CHANGES.md the best. I prefer not to keep this information in the README just to avoid cluttering that file for people who are interested in documentation or contribution guidelines.

My CHANGES.md file has a <h1> at the top that just says ‘Changes’. I don’t have strong opinions on that part. However, the following bit I have very strong opinions on.

You have several sections, following the title. Each section is an <h2> that is the version number of a release followed by a bulleted list of the changes since the previous release. Each item in the list should be a brief summary of a bug fix or feature–no reason to replicate your entire commit history here. Personally, at least for publicly available gems, I like to also credit the author of the change by name.

Each of those sections should go in descending order of version number so that the newest stuff is at the top. There’s also a special version: ‘Unreleased’. Between releases, you don’t yet know what your next version number will be. Will you add a new feature? Break backwards compatibility? Who knows. So I log changes as they’re merged to an ‘Unreleased’ section of CHANGES.md. This way I don’t forget what’s in and it’s easy for someone to see what kind of stuff is coming in the next version (or what’s in master that isn’t released).

Rarely do people sending me Pull Requests add their own entry to CHANGES.md, so usually, I’ll merge their code, and then go add an entry for their change myself. However, I would be delighted if a contributer wrote their own entry.

Releasing

The point under discussion at work fits into this category. I always bump the version number a lone commit, apart from any feature branch or other changes. I feel like there are a couple of advantages:

  1. It provides you an opportunity to review CHANGES.md in it’s final state as you decide how you need to change your version number for release.
  2. It means that you can add a feature that, as you write it, seems like it’ll be the last one before a release and then at the last minute think, “Oh, just one more,” and still have the version bump be the last commit before release.

Relatedly, tag your release commit. I just tag mine with the version number, but you can put a ‘v’ in the front if you like. I don’t care. The point is to make it easy for a consumer of your library to go to Github and easily find the commit that matches whatever released version they’re using. Make sure to push that new tag up to Github.

When I’m ready to release, I do like this:

  1. Review CHANGES.md and select a new version number.
  2. Update the version number in the code.
  3. Change the ‘Unreleased’ heading in CHANGES.md to the new version number.
  4. Run gem build my_gem.gemspec. If it doesn’t build right, stop and fix it. Don’t commit the new version number as part of that fix.
  5. Commit the version bump changes.
  6. Tag the new commit with the version number.
  7. git push && git push --tags && gem push my_gem-1.2.3.gem
  8. rm my_gem-1.2.3.gem.

I’m sure the above could be automated, but it never seemed like enough of a pain in the ass to be worth my while.

So them’s my opinions on gem maintenance. If you tweet or email me questions, I’ll update this post with answers.