Fix for broken master due to unpersisted feature flags

Works around the currently broken CI job by calling
Feature.enabled?(...) inside Gitlab::Experimentation::Experiment#active?
even though we're not actually making full use of it (yet).

Also adds yaml definition files for a few more experiments that have
been added to master since the original MR was reverted.

ee/config/feature_flags/experiment/ci_syntax_templates_experiment_percentage.yml

+---
+name: ci_syntax_templates_experiment_percentage
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/48141
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/281057
+milestone: '13.8'
+type: experiment
+group: group::activation
+default_enabled: false

ee/config/feature_flags/experiment/pipelines_empty_state_experiment_percentage.yml

+---
+name: pipelines_empty_state_experiment_percentage
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/47952
+rollout_issue_url: https://gitlab.com/gitlab-org/growth/team-tasks/-/issues/289
+milestone: '13.8'
+type: experiment
+group: group::activation
+default_enabled: false

ee/config/feature_flags/experiment/trial_during_signup_experiment_percentage.yml

+---
+name: trial_during_signup_experiment_percentage
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/45147/
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/251231
+milestone: '13.8'
+type: experiment
+group: group::conversion
+default_enabled: false

ee/spec/requests/api/experiments_spec.rb

@@ -20,6 +20,8 @@ RSpec.describe API::Experiments do
       end
 
       before do
+        skip_feature_flags_yaml_validation
+        skip_default_enabled_yaml_check
         stub_const('Gitlab::Experimentation::EXPERIMENTS', experiments)
         Feature.enable_percentage_of_time('experiment_1_experiment_percentage', 10)
         Feature.disable('experiment_2_experiment_percentage')

lib/gitlab/experimentation/experiment.rb

@@ -11,11 +11,13 @@ module Gitlab
         @key = key
         @tracking_category = params[:tracking_category]
         @use_backwards_compatible_subject_index = params[:use_backwards_compatible_subject_index]
-
-        @experiment_percentage = Feature.get(:"#{key}#{FEATURE_FLAG_SUFFIX}").percentage_of_time_value # rubocop:disable Gitlab/AvoidFeatureGet
       end
 
       def active?
+        # TODO: just touch a feature flag
+        # Temporary change, we will change `experiment_percentage` in future to `Feature.enabled?
+        Feature.enabled?(feature_flag_name, type: :experiment, default_enabled: :yaml)
+
         ::Gitlab.dev_env_or_com? && experiment_percentage > 0
       end
 
@@ -27,7 +29,17 @@ module Gitlab
 
       private
 
-      attr_reader :experiment_percentage
+      def experiment_percentage
+        feature_flag.percentage_of_time_value
+      end
+
+      def feature_flag
+        Feature.get(feature_flag_name) # rubocop:disable Gitlab/AvoidFeatureGet
+      end
+
+      def feature_flag_name
+        :"#{key}#{FEATURE_FLAG_SUFFIX}"
+      end
     end
   end
 end

spec/lib/gitlab/experimentation/experiment_spec.rb

@@ -14,8 +14,10 @@ RSpec.describe Gitlab::Experimentation::Experiment do
   end
 
   before do
-    feature = double('FeatureFlag', percentage_of_time_value: percentage )
-    expect(Feature).to receive(:get).with(:experiment_key_experiment_percentage).and_return(feature)
+    skip_feature_flags_yaml_validation
+    skip_default_enabled_yaml_check
+    feature = double('FeatureFlag', percentage_of_time_value: percentage, enabled?: true)
+    allow(Feature).to receive(:get).with(:experiment_key_experiment_percentage).and_return(feature)
   end
 
   subject(:experiment) { described_class.new(:experiment_key, **params) }

spec/lib/gitlab/experimentation_spec.rb

@@ -38,6 +38,8 @@ RSpec.describe Gitlab::Experimentation do
       }
     })
 
+    skip_feature_flags_yaml_validation
+    skip_default_enabled_yaml_check
     Feature.enable_percentage_of_time(:backwards_compatible_test_experiment_experiment_percentage, enabled_percentage)
     Feature.enable_percentage_of_time(:test_experiment_experiment_percentage, enabled_percentage)
     allow(Gitlab).to receive(:com?).and_return(true)

spec/support/helpers/stub_experiments.rb

 # frozen_string_literal: true
 
 module StubExperiments
-  SUFFIX = Gitlab::Experimentation::Experiment::FEATURE_FLAG_SUFFIX
-
   # Stub Experiment with `key: true/false`
   #
   # @param [Hash] experiment where key is feature name and value is boolean whether active or not.
@@ -13,7 +11,7 @@ module StubExperiments
     allow(Gitlab::Experimentation).to receive(:active?).and_call_original
 
     experiments.each do |experiment_key, enabled|
-      Feature.persist_used!("#{experiment_key}#{SUFFIX}")
+      Feature.persist_used!("#{experiment_key}#{feature_flag_suffix}")
       allow(Gitlab::Experimentation).to receive(:active?).with(experiment_key) { enabled }
     end
   end
@@ -28,8 +26,14 @@ module StubExperiments
     allow(Gitlab::Experimentation).to receive(:in_experiment_group?).and_call_original
 
     experiments.each do |experiment_key, enabled|
-      Feature.persist_used!("#{experiment_key}#{SUFFIX}")
+      Feature.persist_used!("#{experiment_key}#{feature_flag_suffix}")
       allow(Gitlab::Experimentation).to receive(:in_experiment_group?).with(experiment_key, anything) { enabled }
     end
   end
+
+  private
+
+  def feature_flag_suffix
+    Gitlab::Experimentation::Experiment::FEATURE_FLAG_SUFFIX
+  end
 end

spec/support/helpers/stub_feature_flags.rb

@@ -66,4 +66,8 @@ module StubFeatureFlags
   def skip_feature_flags_yaml_validation
     allow(Feature::Definition).to receive(:valid_usage!)
   end
+
+  def skip_default_enabled_yaml_check
+    allow(Feature::Definition).to receive(:default_enabled?).and_return(false)
+  end
 end