Gemfile development guidelines

When adding a new entry to Gemfile, or upgrading an existing dependency pay attention to the following rules.

Bundler checksum verification

In GitLab 15.5 and later, gem checksums are checked before installation. This verification is still experimental so it is only active for CI.

If the downloaded gem’s checksum does not match the checksum record in Gemfile.checksum, you will see an error saying that Bundler cannot continue installing a gem because there is a potential security issue.

You will see this error as well if you updated, or added a new gem without updating Gemfile.checksum. To fix this error, update the Gemfile.checksum.

You can opt-in to this verification locally by setting the BUNDLER_CHECKSUM_VERIFICATION_OPT_IN environment variable:

bundle install

Setting it to false can also disable it:

bundle install

Updating the checksum file

This needs to be done for any new, or updated gems.

  1. When updating Gemfile.lock, make sure to also update Gemfile.checksum with:

    bundle exec bundler-checksum init
  2. Check and commit the changes for Gemfile.checksum.

No gems fetched from Git repositories

We do not allow gems that are fetched from Git repositories. All gems have to be available in the RubyGems index. We want to minimize external build dependencies and build times. It’s enforced by the RuboCop rule Cop/GemFetcher.

Review the new dependency for quality

We should not add 3rd-party dependencies to GitLab that would not pass our own quality standards. This means that new dependencies should, at a minimum, meet the following criteria:

  • They have an active developer community. At the minimum a maintainer should still be active to merge change requests in case of emergencies.
  • There are no issues open that we know may impact the availability or performance of GitLab.
  • The project is tested using some form of test automation. The test suite must be passing using the Ruby version currently used by GitLab.
  • CI builds for all supported platforms must succeed using the new dependency. For more information, see how to build a package for testing.
  • If the project uses a C extension, consider requesting an additional review from a C or MRI domain expert. C extensions can greatly impact GitLab stability and performance.

Gems that require a domain expert approval

Changes to the following gems require a domain expert review and approval by a backend team member of the group.

For gems not listed in this table, it’s still recommended but not required that you find a domain expert to review changes.

Gem Requires approval by
doorkeeper Manage:Authentication and Authorization
doorkeeper-openid_connect Manage:Authentication and Authorization

Request an Appsec review

When adding a new gem to our Gemfile or even changing versions in Gemfile.lock we strongly recommend that you request a Security review. New gems add an extra security risk for GitLab, and it is important to evaluate this risk before we ship this to production. Technically, just adding a new gem and pushing to a branch in our main gitlab project is a security risk as it will run in CI using your credentials. As such you should evaluate early on if you think this gem seems legitimate before you even install it.

Reviewers should also be aware of our related recommendations for reviewing community contributions and take care before running a pipeline for community contributions that contains changes to Gemfile or Gemfile.lock.

License compliance

Refer to licensing guidelines for ensuring license compliance.

GitLab-created gems

Sometimes we create libraries within our codebase that we want to extract, either because we want to use them in other applications ourselves, or because we think it would benefit the wider community. Extracting code to a gem also means that we can be sure that the gem does not contain any hidden dependencies on our application code.

Read more about Gems development guidelines.

Upgrade Rails

When upgrading the Rails gem and its dependencies, you also should update the following:

You should also update npm packages that follow the current version of Rails:

  • @rails/ujs
    • Run yarn patch-package @rails/ujs after updating this to ensure our local patch file version matches.
  • @rails/actioncable

Upgrading dependencies because of vulnerabilities

When upgrading dependencies because of a vulnerability, we should pin the minimal version of the gem in which the vulnerability was fixed in our Gemfile to avoid accidentally downgrading.

For example, consider that the gem license_finder has thor as its dependency. thor was found vulnerable until its version 1.1.1, which includes the vulnerability fix.

In the Gemfile, make sure to pin thor to 1.1.1. The direct dependency license_finder should already have the version specified.

gem 'license_finder', '~> 6.0'
# Dependency of license_finder with fix for vulnerability
# _link to initial security issue that will become public in time_
gem 'thor', '>= 1.1.1'

Here we’re using the operator >= (greater than or equal to) rather than ~> (pessimistic operator) making it possible to upgrade license_finder or any other gem to a version that depends on thor 1.2.

Similarly, if license_finder had a vulnerability fixed in 6.0.1, we should add:

gem 'license_finder', '~> 6.0', '>= 6.0.1'

This way, other dependencies rather than license_finder can still depend on a newer version of thor, such as 6.0.2, but would not be able to depend on the vulnerable version 6.0.0.

A downgrade like that could happen if we introduced a new dependency that also relied on thor but had its version pinned to a vulnerable one. These changes are easy to miss in the Gemfile.lock. Pinning the version would result in a conflict that would need to be solved.

To avoid upgrading indirect dependencies, we can use bundle update --conservative.

When submitting a merge request including a dependency update, include a link to the Gem diff between the 2 versions in the merge request description. You can find this link on, select Review Changes to generate a comparison between the versions on For example, this is the gem diff for thor 1.0.0 vs 1.0.1. Use the links directly generated from RubyGems, since the links from GitLab or other code-hosting platforms might not reflect the code that’s actually published.