Use cached values from `ProtectedBranch` cache

* Contributes to #366724
* Follow-up for:
!92934

* Feature flag: #368279

**Problem**

After testing new Protected branch cache with `dry_run: true` option, we
can start relying on it.

**Solution**

* Remove `dry_run` code
* Use `ProtectedBranch` cache if FF is on

app/models/protected_branch.rb

@@ -37,7 +37,7 @@ def self.protected?(project, ref_name)
 
   def self.new_cache(project, ref_name)
     if Feature.enabled?(:hash_based_cache_for_protected_branches, project)
-      ProtectedBranches::CacheService.new(project).fetch(ref_name, dry_run: true) do # rubocop: disable CodeReuse/ServiceClass
+      ProtectedBranches::CacheService.new(project).fetch(ref_name) do # rubocop: disable CodeReuse/ServiceClass
         self.matching(ref_name, protected_refs: protected_refs(project)).present?
       end
     end

app/services/protected_branches/cache_service.rb

@@ -7,29 +7,16 @@ class CacheService < ProtectedBranches::BaseService
     CACHE_EXPIRE_IN = 1.day
     CACHE_LIMIT = 1000
 
-    def fetch(ref_name, dry_run: false)
+    def fetch(ref_name)
       record = OpenSSL::Digest::SHA256.hexdigest(ref_name)
 
       Gitlab::Redis::Cache.with do |redis|
         cached_result = redis.hget(redis_key, record)
 
-        decoded_result = Gitlab::Redis::Boolean.decode(cached_result) unless cached_result.nil?
-
-        break decoded_result unless dry_run || decoded_result.nil?
+        break Gitlab::Redis::Boolean.decode(cached_result) unless cached_result.nil?
 
         value = yield
 
-        if dry_run && !decoded_result.nil? && decoded_result != value
-          encoded_ref_name = Gitlab::EncodingHelper.encode_utf8_with_replacement_character(ref_name)
-
-          log_error(
-            'class' => self.class.name,
-            'message' => "Cache mismatch '#{encoded_ref_name}': cached value: #{decoded_result}, real value: #{value}",
-            'project_id' => @project.id,
-            'project_path' => @project.full_path
-          )
-        end
-
         redis.hset(redis_key, record, Gitlab::Redis::Boolean.encode(value))
 
         # If the cache record has too many elements, then something went wrong and

spec/features/merge_request/user_uses_quick_actions_spec.rb

@@ -7,7 +7,7 @@
 # for example, adding quick actions when creating the issue and checking DateTime formats on UI.
 # Because this kind of spec takes more time to run there is no need to add new ones
 # for each existing quick action unless they test something not tested by existing tests.
-RSpec.describe 'Merge request > User uses quick actions', :js do
+RSpec.describe 'Merge request > User uses quick actions', :js, :clean_gitlab_redis_cache do
   include Spec::Support::Helpers::Features::NotesHelpers
 
   let(:project) { create(:project, :public, :repository) }

spec/models/protected_branch_spec.rb

@@ -167,7 +167,7 @@
         expect(described_class.protected?(project, nil)).to eq(false)
       end
 
-      context 'with caching', :use_clean_rails_memory_store_caching do
+      context 'with caching', :clean_gitlab_redis_cache do
         let_it_be(:project) { create(:project, :repository) }
         let_it_be(:protected_branch) { create(:protected_branch, project: project, name: "“jawn”") }
 
@@ -195,8 +195,7 @@
         end
 
         context 'when project is updated' do
-          # Expected to fail, because of fetch(dry_run: true)
-          xit 'does not invalidate a cache' do
+          it 'does not invalidate a cache' do
             expect(described_class).not_to receive(:matching).with(protected_branch.name, protected_refs: anything)
 
             project.touch
@@ -206,8 +205,7 @@
         end
 
         context 'when other project protected branch is updated' do
-          # Expected to fail, because of fetch(dry_run: true)
-          xit 'does not invalidate the current project cache' do
+          it 'does not invalidate the current project cache' do
             expect(described_class).not_to receive(:matching).with(protected_branch.name, protected_refs: anything)
 
             another_project = create(:project)
@@ -217,13 +215,12 @@
           end
         end
 
-        # Expected to fail, because of fetch(dry_run: true)
-        xit 'correctly uses the cached version' do
+        it 'correctly uses the cached version' do
           expect(described_class).not_to receive(:matching)
           expect(described_class.protected?(project, protected_branch.name)).to eq(true)
         end
 
-        context 'when feature flag is off' do
+        context 'when feature flag is off', :use_clean_rails_memory_store_caching do
           let(:feature_flag) { false }
 
           it 'correctly invalidates a cache' do

spec/services/git/branch_push_service_spec.rb

@@ -193,7 +193,7 @@
     end
   end
 
-  describe "Webhooks" do
+  describe "Webhooks", :clean_gitlab_redis_cache do
     before do
       create(:project_hook, push_events: true, project: project)
     end

spec/services/protected_branches/cache_service_spec.rb

@@ -61,38 +61,6 @@
         expect(service.fetch('not-found') { true }).to eq(true)
       end
     end
-
-    context 'when dry_run is on' do
-      it 'does not use cached value' do
-        expect(service.fetch('main', dry_run: true) { true }).to eq(true)
-        expect(service.fetch('main', dry_run: true) { false }).to eq(false)
-      end
-
-      context 'when cache mismatch' do
-        it 'logs an error' do
-          expect(service.fetch('main', dry_run: true) { true }).to eq(true)
-
-          expect(Gitlab::AppLogger).to receive(:error).with(
-            'class' => described_class.name,
-            'message' => /Cache mismatch/,
-            'project_id' => project.id,
-            'project_path' => project.full_path
-          )
-
-          expect(service.fetch('main', dry_run: true) { false }).to eq(false)
-        end
-      end
-
-      context 'when cache matches' do
-        it 'does not log an error' do
-          expect(service.fetch('main', dry_run: true) { true }).to eq(true)
-
-          expect(Gitlab::AppLogger).not_to receive(:error)
-
-          expect(service.fetch('main', dry_run: true) { true }).to eq(true)
-        end
-      end
-    end
   end
 
   describe '#refresh' do