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Safe gem upgrades with pessimize gem

Episode #34

by Federico Iachetti

Working on a Ruby application implies, sooner or later, dealing with a Gemfile, gem versions and gem dependencies. This usually isn't a problem when we first create our project but, as time progresses and gems get mantained, working with multiple libraries becomes a hustle.

Most gems out there are versioned using Semantic versioning, which helps us know when they're safe to be upgraded. But that's just one part of the equation. We also need to deal with actually deciding what to update, when and how. Lets see what I mean by this with an example.

Say we have a project that uses the money gem, as specified in the Gemfile.

source "<https://rubygems.org>"

gem "money"

If we look at the Gemfile.lock file, we can assert that the version that's currently being used in the project is 3.0.1.

GEM
  remote: <https://rubygems.org/>
  specs:
    money (3.0.1)

This doesn't mean that 3.0.1 is the newest available version though. If we run bundle update, we can see that the version for the money gem gets updated to 6.16.0, which actually is the latest one when recording this episode.

$ bundle update
Fetching gem metadata from <http://localhost:9898/>....
Resolving dependencies...
Using bundler 2.3.19
Using concurrent-ruby 1.1.10
Using i18n 1.12.0
Fetching money 6.16.0 (was 3.0.1)
Installing money 6.16.0 (was 3.0.1)
Bundle updated!

This update has now been reflected in the Gemfile.lock file, along with the inclusion of some external dependencies, which won't affect the flow of this episode, but it's worth noting.

GEM
  remote: <https://rubygems.org/>
  specs:
    concurrent-ruby (1.1.10)
    i18n (1.12.0)
      concurrent-ruby (~> 1.0)
    money (6.16.0)
      i18n (>= 0.6.4, <= 2)

This gem update is an unwanted effect. As we saw in episode 033, a change in the MAJOR version of a file signifies that there are breaking changes on that gem. This means that we might have potentially introduced bugs in our system. This is not necessarily true though; it'll depend on the features that changed and the ones that are in use in our code. With that caveat, we should still be very careful when changing a MAJOR version.

Versioning on the Gemfile instead of relying on the Gemfile.lock

The best way to avoid this side effect, is to add the version we desire directly on the Gemfile. We can do this by adding the version as the second string argument to the dependencies gem method call.

source "<https://rubygems.org>"

gem "money", "3.0.1"

By doing this, we make sure to use the exact version we told Bundler to use, in our case, 3.0.1. And it won't change either using bundle install or bundle update, which makes it a safer option.

$ bundle update

Exact versus pessimistic versioning

But there's another option that's still safe: using Pessimistic Versioning. This means allowing the gem to be updated using bundle update but just up to some extent.

For example, we can set our Gemfile to update the money gem without updating the major version, just minor and patch.

We do this using the pessimistic operator and introducing just the major and minor versions.

source "<https://rubygems.org>"

gem "money", "~> 3.0"

And now if we run bundle update, it updates to version 3.7.1

$ bundle update
Fetching gem metadata from <http://localhost:9898/>....
Resolving dependencies...
Using bundler 2.3.19
Using concurrent-ruby 1.1.10
Fetching i18n 0.9.5
Installing i18n 0.9.5
Fetching money 3.7.1 (was 3.0.1)
Installing money 3.7.1 (was 3.0.1)
Bundle updated!

If instead of just MAJOR and MINOR we add the PATCH version as well, the pessimistic operator will allow the gem to be updated without changing the minor or major versions.

source "<https://rubygems.org>"

gem "money", "~> 3.0.1"

As we can see, if we run bundle update, the new version installed is 3.0.5.

$ bundle update
Fetching gem metadata from <http://localhost:9898/>....
Resolving dependencies...
Using bundler 2.3.19
Fetching money 3.0.5 (was 3.0.1)
Installing money 3.0.5 (was 3.0.1)
Bundle updated!

Which is greater than 3.0.1, but the MINOR and MAJOR versions are kept at their current value. It's also worth noting that 3.0.5 is the greatest found version that has the same MAJOR and MINOR versions. Or, saying this a different way, 3.0.5 was the greatest possible PATCH version.

Pessimize to patch and not to minor or major

How pessimistic we are in our Gemfile is a decision that's up to each one of us.

According to Semantic versioning, allowing the MINOR version to change shouldn't be a problem for us, since it means that features have been added to the dependency, but no breaking changes.

source "<https://rubygems.org>"

gem "money", "~> 3.0"

I usually pessimize up to the PATCH version, meaning that I'll allow the PATCH version to be updated by bundle update, but anything above that, I update manually. This is not absolutely necessary, but it brings me peace of mind.

source "<https://rubygems.org>"

gem "money", "~> 3.0.1"

Using pessimize

So far we've been dealing with a project that has one gem dependency ... a very rare occurrence if you ask me.

source "<https://rubygems.org>"

gem "money", "~> 3.0.1"

But what happens when we have a Gemfile with several gems, like this one? Do we have to set the pessimistic version of choice for each individual gem? This seams like a nightmare to deal with.

source "<https://rubygems.org>"

gem "puma"
gem "roda"
gem "awesome_print"
gem "pg"
gem "redis"
gem "money"
gem "shrine"
gem "cloudinary"
gem "shrine-cloudinary"
gem "faker"
gem "dry-struct"
gem "dry-validation"
gem "dry-schema"

For these kind of situations was created the Pessimize gem.

Pessimize allows us to automatically add version numbers to all the gems in our Gemfile using the Pessimistic Version Operator.

Let's start by installing the gem.

$ gem install pessimize
Fetching pessimize-0.4.0.gem
Successfully installed pessimize-0.4.0
1 gem installed

Now that we have it in our system, we can run the pessimize command.

We can ignore the trollop deprecation warning that's shown on the terminal.

$ pessimize
[DEPRECATION] The trollop gem has been renamed to optimist and will no longer be supported. Please switch to optimist as soon as possible.
Backing up Gemfile and Gemfile.lock
 + cp Gemfile Gemfile.backup
 + cp Gemfile.lock Gemfile.lock.backup

~> written 20 gems to Gemfile, constrained to minor version updates

This command will pick up the version numbers from the Gemfile.lockfile and add them as the second argument to the gemmethod of each line in the Gemfile using the pessimistic operator (hence it's name).

source "<https://rubygems.org>"

gem "puma", "~> 5.6"
gem "roda", "~> 3.61"
gem "awesome_print", "~> 1.9"
gem "pg", "~> 1.4"
gem "redis", "~> 5.0"
gem "money", "~> 3.0"
gem "shrine", "~> 3.4"
gem "cloudinary", "~> 1.23"
gem "shrine-cloudinary", "~> 1.1"
gem "faker", "~> 2.23"
gem "dry-struct", "~> 1.4"
gem "dry-validation", "~> 1.8"
gem "dry-schema", "~> 1.10"

By default, it'll pessimize up to the MINOR version, but this can be configured when running the command.

If we pass it the -c flag, we can specify which segment to pessimize to.

For example, if we want to pessimize up to the PATCH version, which is my preferred option, we can run pessimize -c patch

$ pessimize -c patch

Now we have the patch versions pessimized in our Gemfile.

source "<https://rubygems.org>"

gem "puma", "~> 5.6.5"
gem "roda", "~> 3.61.0"
gem "awesome_print", "~> 1.9.2"
gem "pg", "~> 1.4.4"
gem "redis", "~> 5.0.5"
gem "money", "~> 3.0.5"
gem "shrine", "~> 3.4.0"
gem "cloudinary", "~> 1.23.0"
gem "shrine-cloudinary", "~> 1.1.1"
gem "faker", "~> 2.23.0"
gem "dry-struct", "~> 1.4.0"
gem "dry-validation", "~> 1.8.1"
gem "dry-schema", "~> 1.10.6"

Backup files

One ugly side effect of using pessimize like this is that it leaves behind some waste. Specifically two backup files. One for the Gemfile and one for the Gemfile.lock.

$ ls
Gemfile  Gemfile.backup  Gemfile.lock  Gemfile.lock.backup

But since we use version control, these files are not needed.

We can remove them by hand after each use call to the pessimize command.

$ rm Gemfile.backup Gemfile.lock.backup

Or use pass the --no-backup flag to pessimize in order to not create them from the get go.

$ pessimize -c patch --no-backup

And now, there're just not there anymore.

$ ls
Gemfile  Gemfile.lock

What happens with groups and other attributes?

Pessimize also respects groups and other attributes passed to the gem method.

For example, if we have this Gemfile

source "<https://rubygems.org>"

gem "puma", "~> 5.6.5"
gem "roda", "~> 3.61.0"
gem "awesome_print", "~> 1.9.2"
gem "pg", "~> 1.4.4"
gem "redis", "~> 5.0.5"
gem "money", "~> 3.0.5"
gem "shrine", "~> 3.4.0"
gem "cloudinary", "~> 1.23.0"
gem "shrine-cloudinary", "~> 1.1.1"
gem "faker", "~> 2.23.0"
gem "dry-struct", "~> 1.4.0"
gem "dry-validation", "~> 1.8.1"
gem "dry-schema", "~> 1.10.6"

group :test do
  gem "rspec"
  gem "simplecov", require: false
  gem "vcr"
  gem "webmock"
end

And we run pessimize

$ pessimize -c patch --no-backup

It will leave the groupand the require attribute unaffected, so we don't need to take care of anything Gemfile-related by hand. Very convenient!

source "<https://rubygems.org>"

gem "puma", "~> 5.6.5"
gem "roda", "~> 3.61.0"
gem "awesome_print", "~> 1.9.2"
gem "pg", "~> 1.4.4"
gem "redis", "~> 5.0.5"
gem "money", "~> 3.0.5"
gem "shrine", "~> 3.4.0"
gem "cloudinary", "~> 1.23.0"
gem "shrine-cloudinary", "~> 1.1.1"
gem "faker", "~> 2.23.0"
gem "dry-struct", "~> 1.4.0"
gem "dry-validation", "~> 1.8.1"
gem "dry-schema", "~> 1.10.6"

group :test do
  gem "rspec", "~> 3.11.0"
  gem "simplecov", "~> 0.21.2", require: false
  gem "vcr", "~> 6.1.0"
  gem "webmock", "~> 3.18.1"
end

Alias on .zshrc

I use pessimize in every project I work on. In fact, pessimize is on the list of the 3 or 4 gems I install right away when setting up a new Ruby environment.

Since I use it so much and I always use it the same way, I've created two aliases for updating gems.

The first one uses bundle installand the second bundle update.

In both cases, I run pessimize -c patch --no-backupright after installing or updating gems.

alias bp='bundle install && pessimize -c patch --no-backup'
alias bup='bundle update && pessimize -c patch --no-backup'

I run these aliases all the time.They are engraved in my mind.

$ bp

Summary

Semantic versioning is a great tool for managing dependencies in our projects. In this episode we learned how to take advantage of Semantic versioning and to use the pessimize gem to completely automate the process, making our future lives easier and happier.

I invite you to try out pessimize in your next (or even better, your current) project and let me know in the comments if you liked using it.

Thanks

I want to especially thank my recent sponsors,

  • Akilas Yemane
  • Bill Tihen
  • Benjamin Klotz

for supporting this project, I really apreciate it!

Do you know great Ruby gems?

Add your suggestion to our discussion panel!

I'll gladly cover them in the future episodes! Thank you!

Suggest topicTweet #suggestion

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