Guidelines for implementing Enterprise Edition features

Place code in ee/: Put all Enterprise Edition (EE) inside the ee/ top-level directory. The rest of the code must be as close to the Community Edition (CE) files as possible.
Write tests: As with any code, EE features must have good test coverage to prevent regressions. All ee/ code must have corresponding tests in ee/.
Write documentation.: Add documentation to the doc/ directory. Describe the feature and include screenshots, if applicable. Indicate what editions the feature applies to.

Submit a MR to the www-gitlab-com project.: Add the new feature to the EE features list.

SaaS-only feature

Use the following guidelines when you develop a feature that is only applicable for SaaS (for example, a CustomersDot integration).

In general, features should be provided for both SaaS and self-managed deployments. However, there are cases when a feature should only be available on SaaS and this guide will help show how that is accomplished.

It is recommended you use Gitlab::Saas.feature_available?. This enables context rich definitions around the reason the feature is SaaS-only.

Implementing a SaaS-only feature with `Gitlab::Saas.feature_available?`

Adding to the FEATURES constant

See the namespacing concepts guide for help in naming a new SaaS-only feature.

Add the new feature to FEATURE in ee/lib/ee/gitlab/saas.rb.

FEATURES = %i[purchases_additional_minutes some_domain_new_feature_name].freeze

Use the new feature in code with Gitlab::Saas.feature_available?(:some_domain_new_feature_name).

SaaS-only feature definition and validation

This process is meant to ensure consistent SaaS feature usage in the codebase. All SaaS features must:

Be known. Only use SaaS features that are explicitly defined.
Have an owner.

All SaaS features are self-documented in YAML files stored in:

ee/config/saas_features

Each SaaS feature is defined in a separate YAML file consisting of a number of fields:

Field	Required	Description
`name`	yes	Name of the SaaS feature.
`introduced_by_url`	no	The URL to the merge request that introduced the SaaS feature.
`milestone`	no	Milestone in which the SaaS feature was created.
`group`	no	The group that owns the feature flag.

Create a new SaaS feature file definition

The GitLab codebase provides bin/saas-feature.rb, a dedicated tool to create new SaaS feature definitions. The tool asks various questions about the new SaaS feature, then creates a YAML definition in ee/config/saas_features.

Only SaaS features that have a YAML definition file can be used when running the development or testing environments.

❯ bin/saas-feature my_saas_feature
You picked the group 'group::acquisition'

>> URL of the MR introducing the SaaS feature (enter to skip and let Danger provide a suggestion directly in the MR):
?> https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38602
create ee/config/saas_features/my_saas_feature.yml
---
name: my_saas_feature
introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38602
milestone: '16.8'
group: group::acquisition

Opting out of a SaaS-only feature on another SaaS instance (JiHu)

Prepend the ee/lib/ee/gitlab/saas.rb module and override the Gitlab::Saas.feature_available? method.

JH_DISABLED_FEATURES = %i[some_domain_new_feature_name].freeze

override :feature_available?
def feature_available?(feature)
  super && JH_DISABLED_FEATURES.exclude?(feature)
end

Do not use SaaS-only features for functionality in CE

Gitlab::Saas.feature_available? must not appear in CE. See extending CE with EE guide.

SaaS-only features in tests

Introducing a SaaS-only feature into the codebase creates an additional code path that should be tested. It is strongly advised to include automated tests for all code affected by a SaaS-only feature, both when enabled and disabled to ensure the feature works properly.

To enable a SaaS-only feature in a test, use the stub_saas_features helper. For example, to globally disable the purchases_additional_minutes feature flag in a test:

stub_saas_features(purchases_additional_minutes: false)

::Gitlab::Saas.feature_available?(:purchases_additional_minutes) # => false

A common pattern of testing both paths looks like:

it 'purchases/additional_minutes is not available' do
  # tests assuming purchases_additional_minutes is not enabled by default
  ::Gitlab::Saas.feature_available?(:purchases_additional_minutes) # => false
end

context 'when purchases_additional_minutes is available' do
  before do
    stub_saas_features(purchases_additional_minutes: true)
  end

  it 'returns true' do
    ::Gitlab::Saas.feature_available?(:purchases_additional_minutes) # => true
  end
end

Simulate a SaaS instance

If you're developing locally and need your instance to simulate the SaaS (GitLab.com) version of the product:

Export this environment variable:
```
export GITLAB_SIMULATE_SAAS=1
```
There are many ways to pass an environment variable to your local GitLab instance. For example, you can create an env.runit file in the root of your GDK with the above snippet.
Enable Allow use of licensed EE features to make licensed EE features available to projects only if the project namespace's plan includes the feature.
1. On the left sidebar, at the bottom, select Admin area.
2. On the left sidebar, select Settings > General.
3. Expand Account and limit.
4. Select the Allow use of licensed EE features checkbox.
5. Select Save changes.
Ensure the group you want to test the EE feature for is actually using an EE plan:
1. On the left sidebar, at the bottom, select Admin area.
2. On the left sidebar, select Overview > Groups.
3. Identify the group you want to modify, and select Edit.
4. Scroll to Permissions and group features. For Plan, select Ultimate.
5. Select Save changes.

Implement a new EE feature

If you're developing a GitLab Premium or GitLab Ultimate licensed feature, use these steps to add your new feature or extend it.

GitLab license features are added to ee/app/models/gitlab_subscriptions/features.rb. To determine how to modify this file, first discuss how your feature fits into our licensing with your Product Manager.

Use the following questions to guide you:

Is this a new feature, or are you extending an existing licensed feature?
- If your feature already exists, you don't have to modify features.rb, but you must locate the existing feature identifier to guard it.
- If this is a new feature, decide on an identifier, such as my_feature_name, to add to the features.rb file.
Is this a GitLab Premium or GitLab Ultimate feature?
- Based on the plan you choose to use the feature in, add the feature identifier to PREMIUM_FEATURES or ULTIMATE_FEATURES.
Will this feature be available globally (system-wide at the GitLab instance level)?
- Features such as Geo and Database Load Balancing are used by the entire instance and cannot be restricted to individual user namespaces. These features are defined in the instance license. Add these features to GLOBAL_FEATURES.

Guard your EE feature

A licensed feature can only be available to licensed users. You must add a check or guard to determine if users have access to the feature.

To guard your licensed feature:

Locate your feature identifier in ee/app/models/gitlab_subscriptions/features.rb.

Use the following methods, where my_feature_name is your feature identifier:

In a project context:

my_project.licensed_feature_available?(:my_feature_name) # true if available for my_project

In a group or user namespace context:

my_group.licensed_feature_available?(:my_feature_name) # true if available for my_group

For a global (system-wide) feature:

License.feature_available?(:my_feature_name)  # true if available in this instance

Optional. If your global feature is also available to namespaces with a paid plan, combine two feature identifiers to allow both administrators and group users. For example:
```
License.feature_available?(:my_feature_name) || group.licensed_feature_available?(:my_feature_name_for_namespace) # Both admins and group members can see this EE feature
```

Simulate a CE instance when unlicensed

After the implementation of GitLab CE features to work with unlicensed EE instance GitLab Enterprise Edition works like GitLab Community Edition when no license is active.

CE specs should remain untouched as much as possible and extra specs should be added for EE. Licensed features can be stubbed using the spec helper stub_licensed_features in EE::LicenseHelpers.

You can force GitLab to act as CE by either deleting the ee/ directory or by setting the FOSS_ONLY environment variable to something that evaluates as true. The same works for running tests (for example FOSS_ONLY=1 yarn jest).

Simulate a CE instance with a licensed GDK

To simulate a CE instance without deleting the license in a GDK:

Create an env.runit file in the root of your GDK with the line:
```
export FOSS_ONLY=1
```

Then restart the GDK:

gdk restart rails && gdk restart webpack

Remove the line in env.runit if you want to revert back to an EE installation, and repeat step 2.

Run feature specs as CE

When running feature specs as CE, you should ensure that the edition of backend and frontend match. To do so:

Set the FOSS_ONLY=1 environment variable:
```
export FOSS_ONLY=1
```
Start GDK:
```
gdk start
```

Run feature specs:

bin/rspec spec/features/<path_to_your_spec>

Run CI pipelines in a FOSS context

By default, merge request pipelines for development run in an EE-context only. If you are developing features that differ between FOSS and EE, you may wish to run pipelines in a FOSS context as well.

To run pipelines in both contexts, add the ~"pipeline:run-as-if-foss" label to the merge request.

See the As-if-FOSS jobs and cross project downstream pipeline pipelines documentation for more information.

Separation of EE code in the backend

EE-only features

If the feature being developed is not present in any form in CE, we don't need to put the code under the EE namespace. For example, an EE model could go into: ee/app/models/awesome.rb using Awesome as the class name. This is applied not only to models. Here's a list of other examples:

ee/app/controllers/foos_controller.rb
ee/app/finders/foos_finder.rb
ee/app/helpers/foos_helper.rb
ee/app/mailers/foos_mailer.rb
ee/app/models/foo.rb
ee/app/policies/foo_policy.rb
ee/app/serializers/foo_entity.rb
ee/app/serializers/foo_serializer.rb
ee/app/services/foo/create_service.rb
ee/app/validators/foo_attr_validator.rb
ee/app/workers/foo_worker.rb
ee/app/views/foo.html.haml
ee/app/views/foo/_bar.html.haml

This works because for every path that is present in CE's eager-load/auto-load paths, we add the same ee/-prepended path in config/application.rb. This also applies to views.

Testing EE-only backend features

To test an EE class that doesn't exist in CE, create the spec file as you usually would in the ee/spec directory, but without the second ee/ subdirectory. For example, a class ee/app/models/vulnerability.rb would have its tests in ee/spec/models/vulnerability_spec.rb.

By default, licensed features are disabled for specs in specs/. Specs in the ee/spec directory have Starter license initialized by default.

To effectively test your feature you must explicitly enable the feature using the stub_licensed_features helper, for example:

  stub_licensed_features(my_awesome_feature_name: true)

Extend CE features with EE backend code

For features that build on existing CE features, write a module in the EE namespace and inject it in the CE class, on the last line of the file that the class resides in. This makes conflicts less likely to happen during CE to EE merges because only one line is added to the CE class - the line that injects the module. For example, to prepend a module into the User class you would use the following approach:

class User < ActiveRecord::Base
  # ... lots of code here ...
end

User.prepend_mod

Do not use methods such as prepend, extend, and include. Instead, use prepend_mod, extend_mod, or include_mod. These methods will try to find the relevant EE module by the name of the receiver module, for example;

module Vulnerabilities
  class Finding
    #...
  end
end

Vulnerabilities::Finding.prepend_mod

will prepend the module named ::EE::Vulnerabilities::Finding.

If the extending module does not follow this naming convention, you can also provide the module name by using prepend_mod_with, extend_mod_with, or include_mod_with. These methods take a String containing the full module name as the argument, not the module itself, like so;

class User
  #...
end

User.prepend_mod_with('UserExtension')

Since the module would require an EE namespace, the file should also be put in an ee/ sub-directory. For example, we want to extend the user model in EE, so we have a module called ::EE::User put inside ee/app/models/ee/user.rb.

This is also not just applied to models. Here's a list of other examples:

ee/app/controllers/ee/foos_controller.rb
ee/app/finders/ee/foos_finder.rb
ee/app/helpers/ee/foos_helper.rb
ee/app/mailers/ee/foos_mailer.rb
ee/app/models/ee/foo.rb
ee/app/policies/ee/foo_policy.rb
ee/app/serializers/ee/foo_entity.rb
ee/app/serializers/ee/foo_serializer.rb
ee/app/services/ee/foo/create_service.rb
ee/app/validators/ee/foo_attr_validator.rb
ee/app/workers/ee/foo_worker.rb

Testing EE features based on CE features

To test an EE namespaced module that extends a CE class with EE features, create the spec file as you usually would in the ee/spec directory, including the second ee/ subdirectory. For example, an extension ee/app/models/ee/user.rb would have its tests in ee/spec/models/ee/user_spec.rb.

In the RSpec.describe call, use the CE class name where the EE module would be used. For example, in ee/spec/models/ee/user_spec.rb, the test would start with:

RSpec.describe User do
  describe 'ee feature added through extension'
end

Overriding CE methods

To override a method present in the CE codebase, use prepend. It lets you override a method in a class with a method from a module, while still having access the class's implementation with super.

There are a few gotchas with it:

you should always extend ::Gitlab::Utils::Override and use override to guard the overrider method to ensure that if the method gets renamed in CE, the EE override isn't silently forgotten.
when the overrider would add a line in the middle of the CE implementation, you should refactor the CE method and split it in smaller methods. Or create a "hook" method that is empty in CE, and with the EE-specific implementation in EE.
when the original implementation contains a guard clause (for example, return unless condition), we cannot easily extend the behavior by overriding the method, because we can't know when the overridden method (that is, calling super in the overriding method) would want to stop early. In this case, we shouldn't just override it, but update the original method to make it call the other method we want to extend, like a template method pattern. For example, given this base:
```
  class Base
    def execute
      return unless enabled?

      # ...
      # ...
    end
  end
```
Instead of just overriding Base#execute, we should update it and extract the behavior into another method:
```
  class Base
    def execute
      return unless enabled?

      do_something
    end

    private

    def do_something
      # ...
      # ...
    end
  end
```
Then we're free to override that do_something without worrying about the guards:
```
  module EE::Base
    extend ::Gitlab::Utils::Override

    override :do_something
    def do_something
      # Follow the above pattern to call super and extend it
    end
  end
```

When prepending, place them in the ee/ specific sub-directory, and wrap class or module in module EE to avoid naming conflicts.

For example to override the CE implementation of ApplicationController#after_sign_out_path_for:

def after_sign_out_path_for(resource)
  current_application_settings.after_sign_out_path.presence || new_user_session_path
end

Instead of modifying the method in place, you should add prepend to the existing file:

class ApplicationController < ActionController::Base
  # ...

  def after_sign_out_path_for(resource)
    current_application_settings.after_sign_out_path.presence || new_user_session_path
  end

  # ...
end

ApplicationController.prepend_mod_with('ApplicationController')

And create a new file in the ee/ sub-directory with the altered implementation:

module EE
  module ApplicationController
    extend ::Gitlab::Utils::Override

    override :after_sign_out_path_for
    def after_sign_out_path_for(resource)
      if Gitlab::Geo.secondary?
        Gitlab::Geo.primary_node.oauth_logout_url(@geo_logout_state)
      else
        super
      end
    end
  end
end

Overriding CE class methods

The same applies to class methods, except we want to use ActiveSupport::Concern and put extend ::Gitlab::Utils::Override within the block of class_methods. Here's an example:

module EE
  module Groups
    module GroupMembersController
      extend ActiveSupport::Concern

      class_methods do
        extend ::Gitlab::Utils::Override

        override :admin_not_required_endpoints
        def admin_not_required_endpoints
          super.concat(%i[update override])
        end
      end
    end
  end
end

Use self-descriptive wrapper methods

When it's not possible/logical to modify the implementation of a method, then wrap it in a self-descriptive method and use that method.

For example, in GitLab-FOSS, the only user created by the system is Users::Internal.ghost but in EE there are several types of bot-users that aren't really users. It would be incorrect to override the implementation of User#ghost?, so instead we add a method #internal? to app/models/user.rb. The implementation:

def internal?
  ghost?
end

In EE, the implementation ee/app/models/ee/users.rb would be:

override :internal?
def internal?
  super || bot?
end

Code in `config/routes`

When we add draw :admin in config/routes.rb, the application tries to load the file located in config/routes/admin.rb, and also try to load the file located in ee/config/routes/admin.rb.

In EE, it should at least load one file, at most two files. If it cannot find any files, an error is raised. In CE, since we don't know if an an EE route exists, it doesn't raise any errors even if it cannot find anything.

This means if we want to extend a particular CE route file, just add the same file located in ee/config/routes. If we want to add an EE only route, we could still put draw :ee_only in both CE and EE, and add ee/config/routes/ee_only.rb in EE, similar to render_if_exists.

Code in `app/controllers/`

In controllers, the most common type of conflict is with before_action that has a list of actions in CE but EE adds some actions to that list.

The same problem often occurs for params.require / params.permit calls.

Mitigations

Separate CE and EE actions/keywords. For instance for params.require in ProjectsController:

def project_params
  params.require(:project).permit(project_params_attributes)
end

# Always returns an array of symbols, created however best fits the use case.
# It _should_ be sorted alphabetically.
def project_params_attributes
  %i[
    description
    name
    path
  ]
end

In the EE::ProjectsController module:

def project_params_attributes
  super + project_params_attributes_ee
end

def project_params_attributes_ee
  %i[
    approvals_before_merge
    approver_group_ids
    approver_ids
    ...
  ]
end

Code in `app/models/`

EE-specific models should be defined in ee/app/models/.

To override a CE model create the file in ee/app/models/ee/ and add new code to a prepended block.

ActiveRecord enums should be entirely defined in FOSS.

Code in `app/views/`

It's a very frequent problem that EE is adding some specific view code in a CE view. For instance the approval code in the project's settings page.

Mitigations

Blocks of code that are EE-specific should be moved to partials. This avoids conflicts with big chunks of HAML code that are not fun to resolve when you add the indentation to the equation.

EE-specific views should be placed in ee/app/views/, using extra sub-directories if appropriate.

Using `render_if_exists`

Instead of using regular render, we should use render_if_exists, which doesn't render anything if it cannot find the specific partial. We use this so that we could put render_if_exists in CE, keeping code the same between CE and EE.

The advantages of this:

Very clear hints about where we're extending EE views while reading CE code.

The disadvantage of this:

If we have typos in the partial name, it would be silently ignored.

Caveats

The render_if_exists view path argument must be relative to app/views/ and ee/app/views. Resolving an EE template path that is relative to the CE view path doesn't work.

- # app/views/projects/index.html.haml

= render_if_exists 'button' # Will not render `ee/app/views/projects/_button` and will quietly fail
= render_if_exists 'projects/button' # Will render `ee/app/views/projects/_button`

Using `render_ce`

For render and render_if_exists, they search for the EE partial first, and then CE partial. They would only render a particular partial, not all partials with the same name. We could take the advantage of this, so that the same partial path (for example, projects/settings/archive) could be referring to the CE partial in CE (that is, app/views/projects/settings/_archive.html.haml), while EE partial in EE (that is, ee/app/views/projects/settings/_archive.html.haml). This way, we could show different things between CE and EE.

However sometimes we would also want to reuse the CE partial in EE partial because we might just want to add something to the existing CE partial. We could workaround this by adding another partial with a different name, but it would be tedious to do so.

In this case, we could as well just use render_ce which would ignore any EE partials. One example would be ee/app/views/projects/settings/_archive.html.haml:

- return if @project.marked_for_deletion?
= render_ce 'projects/settings/archive'

In the above example, we can't use render 'projects/settings/archive' because it would find the same EE partial, causing infinite recursion. Instead, we could use render_ce so it ignores any partials in ee/ and then it would render the CE partial (that is, app/views/projects/settings/_archive.html.haml) for the same path (that is, projects/settings/archive). This way we could easily wrap around the CE partial.

Code in `lib/gitlab/background_migration/`

When you create EE-only background migrations, you have to plan for users that downgrade GitLab EE to CE. In other words, every EE-only migration has to be present in CE code but with no implementation, instead you need to extend it on EE side.

GitLab CE:

# lib/gitlab/background_migration/prune_orphaned_geo_events.rb

module Gitlab
  module BackgroundMigration
    class PruneOrphanedGeoEvents
      def perform(table_name)
      end
    end
  end
end

Gitlab::BackgroundMigration::PruneOrphanedGeoEvents.prepend_mod_with('Gitlab::BackgroundMigration::PruneOrphanedGeoEvents')

GitLab EE:

# ee/lib/ee/gitlab/background_migration/prune_orphaned_geo_events.rb

module EE
  module Gitlab
    module BackgroundMigration
      module PruneOrphanedGeoEvents
        extend ::Gitlab::Utils::Override

        override :perform
        def perform(table_name = EVENT_TABLES.first)
          return if ::Gitlab::Database.read_only?

          deleted_rows = prune_orphaned_rows(table_name)
          table_name   = next_table(table_name) if deleted_rows.zero?

          ::BackgroundMigrationWorker.perform_in(RESCHEDULE_DELAY, self.class.name.demodulize, table_name) if table_name
        end
      end
    end
  end
end

Code in `app/graphql/`

EE-specific mutations, resolvers, and types should be added to ee/app/graphql/{mutations,resolvers,types}.

To override a CE mutation, resolver, or type, create the file in ee/app/graphql/ee/{mutations,resolvers,types} and add new code to a prepended block.

For example, if CE has a mutation called Mutations::Tanukis::Create and you wanted to add a new argument, place the EE override in ee/app/graphql/ee/mutations/tanukis/create.rb:

module EE
  module Mutations
    module Tanukis
      module Create
        extend ActiveSupport::Concern

        prepended do
          argument :name,
                   GraphQL::Types::String,
                   required: false,
                   description: 'Tanuki name'
        end
      end
    end
  end
end

Code in `lib/`

Place EE-specific logic in the top-level EE module namespace. Namespace the class beneath the EE module as you usually would.

For example, if CE has LDAP classes in lib/gitlab/ldap/ then you would place EE-specific LDAP classes in ee/lib/ee/gitlab/ldap.

Code in `lib/api/`

It can be very tricky to extend EE features by a single line of prepend_mod_with, and for each different Grape feature, we might need different strategies to extend it. To apply different strategies easily, we would use extend ActiveSupport::Concern in the EE module.

Put the EE module files following Extend CE features with EE backend code.

EE API routes

For EE API routes, we put them in a prepended block:

module EE
  module API
    module MergeRequests
      extend ActiveSupport::Concern

      prepended do
        params do
          requires :id, types: [String, Integer], desc: 'The ID or URL-encoded path of the project'
        end
        resource :projects, requirements: ::API::API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
          # ...
        end
      end
    end
  end
end

Note that due to namespace differences, we need to use the full qualifier for some constants.

EE parameters

We can define params and use use in another params definition to include parameters defined in EE. However, we need to define the "interface" first in CE in order for EE to override it. We don't have to do this in other places due to prepend_mod_with, but Grape is complex internally and we couldn't easily do that, so we follow regular object-oriented practices that we define the interface first here.

For example, suppose we have a few more optional parameters for EE. We can move the parameters out of the Grape::API::Instance class to a helper module, so we can inject it before it would be used in the class.

module API
  class Projects < Grape::API::Instance
    helpers Helpers::ProjectsHelpers
  end
end

Given this CE API params:

module API
  module Helpers
    module ProjectsHelpers
      extend ActiveSupport::Concern
      extend Grape::API::Helpers

      params :optional_project_params_ce do
        # CE specific params go here...
      end

      params :optional_project_params_ee do
      end

      params :optional_project_params do
        use :optional_project_params_ce
        use :optional_project_params_ee
      end
    end
  end
end

API::Helpers::ProjectsHelpers.prepend_mod_with('API::Helpers::ProjectsHelpers')

We could override it in EE module:

module EE
  module API
    module Helpers
      module ProjectsHelpers
        extend ActiveSupport::Concern

        prepended do
          params :optional_project_params_ee do
            # EE specific params go here...
          end
        end
      end
    end
  end
end

EE helpers

To make it easy for an EE module to override the CE helpers, we need to define those helpers we want to extend first. Try to do that immediately after the class definition to make it easy and clear:

module API
  module Ci
    class JobArtifacts < Grape::API::Instance
      # EE::API::Ci::JobArtifacts would override the following helpers
      helpers do
        def authorize_download_artifacts!
          authorize_read_builds!
        end
      end
    end
  end
end

API::Ci::JobArtifacts.prepend_mod_with('API::Ci::JobArtifacts')

And then we can follow regular object-oriented practices to override it:

module EE
  module API
    module Ci
      module JobArtifacts
        extend ActiveSupport::Concern

        prepended do
          helpers do
            def authorize_download_artifacts!
              super
              check_cross_project_pipelines_feature!
            end
          end
        end
      end
    end
  end
end

EE-specific behavior

Sometimes we need EE-specific behavior in some of the APIs. Usually we could use EE methods to override CE methods, however API routes are not methods and therefore cannot be overridden. We need to extract them into a standalone method, or introduce some "hooks" where we could inject behavior in the CE route. Something like this:

module API
  class MergeRequests < Grape::API::Instance
    helpers do
      # EE::API::MergeRequests would override the following helpers
      def update_merge_request_ee(merge_request)
      end
    end

    put ':id/merge_requests/:merge_request_iid/merge' do
      merge_request = find_project_merge_request(params[:merge_request_iid])

      # ...

      update_merge_request_ee(merge_request)

      # ...
    end
  end
end

API::MergeRequests.prepend_mod_with('API::MergeRequests')

Note that update_merge_request_ee doesn't do anything in CE, but then we could override it in EE:

module EE
  module API
    module MergeRequests
      extend ActiveSupport::Concern

      prepended do
        helpers do
          def update_merge_request_ee(merge_request)
            # ...
          end
        end
      end
    end
  end
end

EE `route_setting`

It's very hard to extend this in an EE module, and this is storing some meta-data for a particular route. Given that, we could leave the EE route_setting in CE as it doesn't hurt and we don't use those meta-data in CE.

We could revisit this policy when we're using route_setting more and whether or not we really need to extend it from EE. For now we're not using it much.

Utilizing class methods for setting up EE-specific data

Sometimes we need to use different arguments for a particular API route, and we can't easily extend it with an EE module because Grape has different context in different blocks. In order to overcome this, we need to move the data to a class method that resides in a separate module or class. This allows us to extend that module or class before its data is used, without having to place a prepend_mod_with in the middle of CE code.

For example, in one place we need to pass an extra argument to at_least_one_of so that the API could consider an EE-only argument as the least argument. We would approach this as follows:

# api/merge_requests/parameters.rb
module API
  class MergeRequests < Grape::API::Instance
    module Parameters
      def self.update_params_at_least_one_of
        %i[
          assignee_id
          description
        ]
      end
    end
  end
end

API::MergeRequests::Parameters.prepend_mod_with('API::MergeRequests::Parameters')

# api/merge_requests.rb
module API
  class MergeRequests < Grape::API::Instance
    params do
      at_least_one_of(*Parameters.update_params_at_least_one_of)
    end
  end
end

And then we could easily extend that argument in the EE class method:

module EE
  module API
    module MergeRequests
      module Parameters
        extend ActiveSupport::Concern

        class_methods do
          extend ::Gitlab::Utils::Override

          override :update_params_at_least_one_of
          def update_params_at_least_one_of
            super.push(*%i[
              squash
            ])
          end
        end
      end
    end
  end
end

It could be annoying if we need this for a lot of routes, but it might be the simplest solution right now.

This approach can also be used when models define validations that depend on class methods. For example:

# app/models/identity.rb
class Identity < ActiveRecord::Base
  def self.uniqueness_scope
    [:provider]
  end

  prepend_mod_with('Identity')

  validates :extern_uid,
    allow_blank: true,
    uniqueness: { scope: uniqueness_scope, case_sensitive: false }
end

# ee/app/models/ee/identity.rb
module EE
  module Identity
    extend ActiveSupport::Concern

    class_methods do
      extend ::Gitlab::Utils::Override

      def uniqueness_scope
        [*super, :saml_provider_id]
      end
    end
  end
end

Instead of taking this approach, we would refactor our code into the following:

# ee/app/models/ee/identity/uniqueness_scopes.rb
module EE
  module Identity
    module UniquenessScopes
      extend ActiveSupport::Concern

      class_methods do
        extend ::Gitlab::Utils::Override

        def uniqueness_scope
          [*super, :saml_provider_id]
        end
      end
    end
  end
end

# app/models/identity/uniqueness_scopes.rb
class Identity < ActiveRecord::Base
  module UniquenessScopes
    def self.uniqueness_scope
      [:provider]
    end
  end
end

Identity::UniquenessScopes.prepend_mod_with('Identity::UniquenessScopes')

# app/models/identity.rb
class Identity < ActiveRecord::Base
  validates :extern_uid,
    allow_blank: true,
    uniqueness: { scope: Identity::UniquenessScopes.scopes, case_sensitive: false }
end

Code in `spec/`

When you're testing EE-only features, avoid adding examples to the existing CE specs. Also do not change existing CE examples, since they should remain working as-is when EE is running without a license.

Instead place EE specs in the ee/spec folder.

Code in `spec/factories`

Use FactoryBot.modify to extend factories already defined in CE.

Note that you cannot define new factories (even nested ones) inside the FactoryBot.modify block. You can do so in a separate FactoryBot.define block as shown in the example below:

# ee/spec/factories/notes.rb
FactoryBot.modify do
  factory :note do
    trait :on_epic do
      noteable { create(:epic) }
      project nil
    end
  end
end

FactoryBot.define do
  factory :note_on_epic, parent: :note, traits: [:on_epic]
end

Separation of EE code in the frontend

To separate EE-specific JS-files, move the files into an ee folder.

For example there can be an app/assets/javascripts/protected_branches/protected_branches_bundle.js and an EE counterpart ee/app/assets/javascripts/protected_branches/protected_branches_bundle.js. The corresponding import statement would then look like this:

// app/assets/javascripts/protected_branches/protected_branches_bundle.js
import bundle from '~/protected_branches/protected_branches_bundle.js';

// ee/app/assets/javascripts/protected_branches/protected_branches_bundle.js
// (only works in EE)
import bundle from 'ee/protected_branches/protected_branches_bundle.js';

// in CE: app/assets/javascripts/protected_branches/protected_branches_bundle.js
// in EE: ee/app/assets/javascripts/protected_branches/protected_branches_bundle.js
import bundle from 'ee_else_ce/protected_branches/protected_branches_bundle.js';

Add new EE-only features in the frontend

If the feature being developed is not present in CE, add your entry point in ee/. For example:

# Add HTML element to mount
ee/app/views/admin/geo/designs/index.html.haml

# Init the application
ee/app/assets/javascripts/pages/ee_only_feature/index.js

# Mount the feature
ee/app/assets/javascripts/ee_only_feature/index.js

Feature guarding licensed_feature_available? and License.feature_available? typical occurs in the controller, as described in the backend guide.

Testing EE-only frontend features

Add your EE tests to ee/spec/frontend/ following the same directory structure you use for CE.

Check the note under Testing EE-only backend features regarding enabling licensed features.

Extend CE features with EE frontend code

Use the push_licensed_feature to guard frontend features that extend existing views:

# ee/app/controllers/ee/admin/my_controller.rb
before_action do
  push_licensed_feature(:my_feature_name) # for global features
end

# ee/app/controllers/ee/group/my_controller.rb
before_action do
  push_licensed_feature(:my_feature_name, @group) # for group pages
end

# ee/app/controllers/ee/project/my_controller.rb
before_action do
  push_licensed_feature(:my_feature_name, @group) # for group pages
  push_licensed_feature(:my_feature_name, @project) # for project pages
end

Verify your feature appears in gon.licensed_features in the browser console.

Extend Vue applications with EE Vue components

EE licensed features that enhance existing functionality in the UI add new elements or interactions to your Vue application as components.

You can import EE components inside CE components to add EE features.

Use an ee_component alias to import an EE component. In EE the ee_component import alias points to the ee/app/assets/javascripts directory. While in CE this alias will be resolved to an empty component that renders nothing.

Here is an example of an EE component imported to a CE component:

<script>
// app/assets/javascripts/feature/components/form.vue

// In EE this will be resolved as `ee/app/assets/javascripts/feature/components/my_ee_component.vue`
// In CE as `app/assets/javascripts/vue_shared/components/empty_component.js`
import MyEeComponent from 'ee_component/feature/components/my_ee_component.vue';

export default {
  components: {
    MyEeComponent,
  },
};
</script>

<template>
  <div>
    <!-- ... -->
    <my-ee-component/>
    <!-- ... -->
  </div>
</template>

NOTE: An EE component can be imported asynchronously if its rendering within CE codebase relies on some check (e.g. a feature flag check).

Check glFeatures to ensure that the Vue components are guarded. The components render only when the license is present.

<script>
// ee/app/assets/javascripts/feature/components/special_component.vue

import glFeatureFlagMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';

export default {
  mixins: [glFeatureFlagMixin()],
  computed: {
    shouldRenderComponent() {
      // Comes from gon.licensed_features as a camel-case version of `my_feature_name`
      return this.glFeatures.myFeatureName;
    }
  },
};
</script>

<template>
  <div v-if="shouldRenderComponent">
    <!-- EE licensed feature UI -->
  </div>
</template>

NOTE: Do not use mixins unless ABSOLUTELY NECESSARY. Try to find an alternative pattern.

Recommended alternative approach (named/scoped slots)

We can use slots and/or scoped slots to achieve the same thing as we did with mixins. If you only need an EE component there is no need to create the CE component.

First, we have a CE component that can render a slot in case we need EE template and functionality to be decorated on top of the CE base.

// ./ce/my_component.vue

<script>
export default {
  props: {
    tooltipDefaultText: {
      type: String,
    },
  },
  computed: {
    tooltipText() {
      return this.tooltipDefaultText || "5 issues please";
    }
  },
}
</script>

<template>
  <span v-gl-tooltip :title="tooltipText" class="ce-text">Community Edition Only Text</span>
  <slot name="ee-specific-component">
</template>

Next, we render the EE component, and inside of the EE component we render the CE component and add additional content in the slot.

// ./ee/my_component.vue

<script>
export default {
  computed: {
    tooltipText() {
      if (this.weight) {
        return "5 issues with weight 10";
      }
    }
  },
  methods: {
    submit() {
      // do something.
    }
  },
}
</script>

<template>
  <my-component :tooltipDefaultText="tooltipText">
    <template #ee-specific-component>
      <span class="some-ee-specific">EE Specific Value</span>
      <button @click="submit">Click Me</button>
    </template>
  </my-component>
</template>

Finally, wherever the component is needed we can require it like so

import MyComponent from 'ee_else_ce/path/my_component'.vue

this way the correct component is included for either the CE or EE implementation

For EE components that need different results for the same computed values, we can pass in props to the CE wrapper as seen in the example.

EE extra HTML
- For the templates that have extra HTML in EE we should move it into a new component and use the ee_else_ce import alias

Extend other JS code

To extend JS files, complete the following steps:

Use the ee_else_ce helper, where that EE only code must be inside the ee/ folder.
1. Create an EE file with only the EE, and extend the CE counterpart.
2. For code inside functions that can't be extended, move the code to a new file and use ee_else_ce helper:

  import eeCode from 'ee_else_ce/ee_code';

  function test() {
    const test = 'a';

    eeCode();

    return test;
  }

In some cases, you'll need to extend other logic in your application. To extend your JS modules, create an EE version of the file and extend it with your custom logic:

// app/assets/javascripts/feature/utils.js

export const myFunction = () => {
  // ...
};

// ... other CE functions ...

// ee/app/assets/javascripts/feature/utils.js
import {
  myFunction as ceMyFunction,
} from '~/feature/utils';

/* eslint-disable import/export */

// Export same utils as CE
export * from '~/feature/utils';

// Only override `myFunction`
export const myFunction = () => {
  const result = ceMyFunction();
  // add EE feature logic
  return result;
};

/* eslint-enable import/export */

Testing modules using EE/CE aliases

When writing Frontend tests, if the module under test imports other modules with ee_else_ce/... and these modules are also needed by the relevant test, then the relevant test must import these modules with ee_else_ce/.... This avoids unexpected EE or FOSS failures, and helps ensure the EE behaves like CE when it is unlicensed.

For example:

<script>
// ~/foo/component_under_test.vue

import FriendComponent from 'ee_else_ce/components/friend.vue;'

export default {
  name: 'ComponentUnderTest',
  components: { FriendComponent }.
}
</script>

<template>
  <friend-component />
</template>

// spec/frontend/foo/component_under_test_spec.js

// ...
// because we referenced the component using ee_else_ce we have to do the same in the spec.
import Friend from 'ee_else_ce/components/friend.vue;'

describe('ComponentUnderTest', () => {
  const findFriend = () => wrapper.find(Friend);

  it('renders friend', () => {
    // This would fail in CE if we did `ee/component...`
    // and would fail in EE if we did `~/component...`
    expect(findFriend().exists()).toBe(true);
  });
});

SCSS code in `assets/stylesheets`

If a component you're adding styles for is limited to EE, it is better to have a separate SCSS file in an appropriate directory within app/assets/stylesheets.

In some cases, this is not entirely possible or creating dedicated SCSS file is an overkill, for example, a text style of some component is different for EE. In such cases, styles are usually kept in a stylesheet that is common for both CE and EE, and it is wise to isolate such ruleset from rest of CE rules (along with adding comment describing the same) to avoid conflicts during CE to EE merge.

// Bad
.section-body {
  .section-title {
    background: $gl-header-color;
  }

  &.ee-section-body {
    .section-title {
      background: $gl-header-color-cyan;
    }
  }
}

// Good
.section-body {
  .section-title {
    background: $gl-header-color;
  }
}

// EE-specific start
.section-body.ee-section-body {
  .section-title {
    background: $gl-header-color-cyan;
  }
}
// EE-specific end

GitLab-svgs

Conflicts in app/assets/images/icons.json or app/assets/images/icons.svg can be resolved by regenerating those assets with yarn run svg.