in Developer Experience

gem-compare: Releasing a new gem version with confidence

What do you usually do when releasing a new version of gems? Running test suite? Something more? I like to use my tool on tracking changes in RubyGems gem-compare as it gives me a little bit more confidence on what am I actually releasing. Here’s how I do it.

Today I wanted to release a new version of fog-libvirt gem, so I checked out the sources, ran git pull, updated the version in lib, ran the test suite again and build the gem:

$ rake build
  Successfully built RubyGem
  Name: fog-libvirt
  Version: 0.0.2
  File: fog-libvirt-0.0.2.gem
mv fog-libvirt-0.0.2.gem pkg
$ cd pkg

I was almost ready to gem push, but it’s always nice to get a little bit more confidence if we can. For instance I was unsure whether my .gemspec wasn’t broken or whether I didn’t merge a PR that changed permissions on files in an unexpected way. And for that we can use gem-compare, a RubyGems plugin to compare gems.

If you don’t have gem-compare plugin installed, you can install it by running:

$ gem install gem-compare

With gem-compare I was are able to run the comparison of the old version (0.0.1 in this case) with the version I was about to release (0.0.2). gem-compare than went and compared the versions for me. This comparison includes RubyGems meta-data including dependencies, gem’s files including permissions as well as Gemfiles. Here is what it showed me before pushing a new version of fog-libvirt:

$ gem compare fog-libvirt 0.0.1 0.0.2 -k
Fetching: fog-libvirt-0.0.1.gem (100%)
Compared versions: ["0.0.1", "0.0.2"]
  DIFFERENT date:
    0.0.1: 2015-04-13 00:00:00 UTC
    0.0.2: 2015-06-16 00:00:00 UTC
  DIFFERENT version:
    0.0.1: 0.0.1
    0.0.2: 0.0.2
  DIFFERENT files:
    0.0.1->0.0.2:
      * Added:
            lib/fog/libvirt/requests/compute/upload_volume.rb
              (!) Unexpected permissions: 100664
            minitests/server/user_data_iso_test.rb
              (!) Unexpected permissions: 100664
            minitests/test_helper.rb
              (!) Unexpected permissions: 100664
      * Changed:
            Rakefile +7/-2
            fog-libvirt.gemspec +5/-2
            lib/fog/libvirt/compute.rb +1/-0
            lib/fog/libvirt/models/compute/server.rb +33/-0
            lib/fog/libvirt/models/compute/volume.rb +5/-0
            lib/fog/libvirt/version.rb +1/-1
            tests/libvirt/models/compute/server_tests.rb +0/-1
  DIFFERENT test_files:
    0.0.1->0.0.2:
      * Changed:
            tests/libvirt/models/compute/server_tests.rb +0/-1
  DIFFERENT development dependencies:
    0.0.1->0.0.2:
      * Deleted:
            thor [">= 0"] (development)
            redcarpet [">= 0"] (development)
      * Added:
            mocha ["~> 1.1.0"] (development)

Note that I ran the gem compare command with -k switch. This is important here because the 0.0.2 version is not released yet and -k prefers to use already downloaded gems in the current directory.

Also note that gem-compare warned me about file permissions being set to 100664, because it expects them to be 100644. This is not a big deal and I am not sure what’s a better default so feel free to ignore that.

I hope that this tool can help you be a little bit more confident about what you release or what are you updating to. I already wrote a little bit about gem-compare on Medium, so you can go and read that piece too.

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