Allow setting feature flags per GitLab group

Building on support for setting feature flags by project, this adds
support for setting them by GitLab group path.

This is different from setting them by Flipper feature_groups, which
are for batch updating pre-registered collections.

changelogs/unreleased/jej-feature-gates-can-be-set-by-group-path.yml

+---
+title: Allow setting feature flags per GitLab group through the API
+merge_request: 25022
+author:
+type: added

doc/api/features.md

@@ -60,10 +60,11 @@ POST /features/:name
 | `value` | integer/string | yes | `true` or `false` to enable/disable, or an integer for percentage of time |
 | `feature_group` | string | no | A Feature group name |
 | `user` | string | no | A GitLab username |
+| `group` | string | no | A GitLab group's path, for example 'gitlab-org' |
 | `project` | string | no | A projects path, for example 'gitlab-org/gitlab-ce' |
 
 Note that you can enable or disable a feature for a `feature_group`, a `user`,
-and a `project` in a single API call.
+a `group`, and a `project` in a single API call.
 
 ```bash
 curl --data "value=30" --header "PRIVATE-TOKEN: <your_access_token>" https://gitlab.example.com/api/v4/features/new_library

lib/api/features.rb

@@ -42,6 +42,7 @@ module API
         requires :value, type: String, desc: '`true` or `false` to enable/disable, an integer for percentage of time'
         optional :feature_group, type: String, desc: 'A Feature group name'
         optional :user, type: String, desc: 'A GitLab username'
+        optional :group, type: String, desc: "A GitLab group's path, such as 'gitlab-org'"
         optional :project, type: String, desc: 'A projects path, like gitlab-org/gitlab-ce'
       end
       post ':name' do

lib/feature.rb

@@ -111,11 +111,11 @@ class Feature
     end
 
     def gate_specified?
-      %i(user project feature_group).any? { |key| params.key?(key) }
+      %i(user project group feature_group).any? { |key| params.key?(key) }
     end
 
     def targets
-      [feature_group, user, project].compact
+      [feature_group, user, project, group].compact
     end
 
     private
@@ -139,5 +139,11 @@ class Feature
 
       Project.find_by_full_path(params[:project])
     end
+
+    def group
+      return unless params.key?(:group)
+
+      Group.find_by_full_path(params[:group])
+    end
   end
 end

spec/lib/feature_spec.rb

@@ -186,13 +186,14 @@ describe Feature do
   describe Feature::Target do
     describe '#targets' do
       let(:project) { create(:project) }
+      let(:group) { create(:group) }
       let(:user_name) { project.owner.username }
 
-      subject { described_class.new(user: user_name, project: project.full_path) }
+      subject { described_class.new(user: user_name, project: project.full_path, group: group.full_path) }
 
       it 'returns all found targets' do
         expect(subject.targets).to be_an(Array)
-        expect(subject.targets).to eq([project.owner, project])
+        expect(subject.targets).to eq([project.owner, project, group])
       end
     end
   end

spec/requests/api/features_spec.rb

@@ -163,6 +163,40 @@ describe API::Features do
         end
       end
 
+      context 'when enabling for a group by path' do
+        context 'when the group exists' do
+          it 'sets the feature gate' do
+            group = create(:group)
+
+            post api("/features/#{feature_name}", admin), params: { value: 'true', group: group.full_path }
+
+            expect(response).to have_gitlab_http_status(201)
+            expect(json_response).to eq(
+              'name' => 'my_feature',
+              'state' => 'conditional',
+              'gates' => [
+                { 'key' => 'boolean', 'value' => false },
+                { 'key' => 'actors', 'value' => ["Group:#{group.id}"] }
+              ])
+          end
+        end
+
+        context 'when the group does not exist' do
+          it 'sets no new values and keeps the feature disabled' do
+            post api("/features/#{feature_name}", admin), params: { value: 'true', group: 'not/a/group' }
+
+            expect(response).to have_gitlab_http_status(201)
+            expect(json_response).to eq(
+              "name" => "my_feature",
+              "state" => "off",
+              "gates" => [
+                { "key" => "boolean", "value" => false }
+              ]
+            )
+          end
+        end
+      end
+
       it 'creates a feature with the given percentage if passed an integer' do
         post api("/features/#{feature_name}", admin), params: { value: '50' }