Enable frozen string in app/serializers/**/*.rbrepo-forks/gitlab-ce-frozen-string-enable-app-serializers

Partially addresses #47424.

100 files changed, 216 insertions, 8 deletions

diff --git a/app/serializers/analytics_build_entity.rb b/app/serializers/analytics_build_entity.rb
index bdc22d71202..99663c8d5eb 100644
--- a/app/serializers/analytics_build_entity.rb
+++ b/app/serializers/analytics_build_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsBuildEntity < Grape::Entity
   include RequestAwareEntity
   include EntityDateHelper
diff --git a/app/serializers/analytics_build_serializer.rb b/app/serializers/analytics_build_serializer.rb
index f172d67d356..9c9f76a1c28 100644
--- a/app/serializers/analytics_build_serializer.rb
+++ b/app/serializers/analytics_build_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsBuildSerializer < BaseSerializer
   entity AnalyticsBuildEntity
 end
diff --git a/app/serializers/analytics_commit_entity.rb b/app/serializers/analytics_commit_entity.rb
index 402cecbfd08..b25c603c9f0 100644
--- a/app/serializers/analytics_commit_entity.rb
+++ b/app/serializers/analytics_commit_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsCommitEntity < CommitEntity
   include EntityDateHelper
 
diff --git a/app/serializers/analytics_commit_serializer.rb b/app/serializers/analytics_commit_serializer.rb
index cdbfecf2b70..0f65687a3c0 100644
--- a/app/serializers/analytics_commit_serializer.rb
+++ b/app/serializers/analytics_commit_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsCommitSerializer < BaseSerializer
   entity AnalyticsCommitEntity
 end
diff --git a/app/serializers/analytics_generic_serializer.rb b/app/serializers/analytics_generic_serializer.rb
index 9f4859e8410..10391c13034 100644
--- a/app/serializers/analytics_generic_serializer.rb
+++ b/app/serializers/analytics_generic_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsGenericSerializer < BaseSerializer
   def represent(resource, opts = {})
     resource.symbolize_keys!
diff --git a/app/serializers/analytics_issue_entity.rb b/app/serializers/analytics_issue_entity.rb
index b7d95ea020f..ab15bd0ac7a 100644
--- a/app/serializers/analytics_issue_entity.rb
+++ b/app/serializers/analytics_issue_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsIssueEntity < Grape::Entity
   include RequestAwareEntity
   include EntityDateHelper
diff --git a/app/serializers/analytics_issue_serializer.rb b/app/serializers/analytics_issue_serializer.rb
index 4fb3e8f1bb4..4a1777276a4 100644
--- a/app/serializers/analytics_issue_serializer.rb
+++ b/app/serializers/analytics_issue_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsIssueSerializer < AnalyticsGenericSerializer
   entity AnalyticsIssueEntity
 end
diff --git a/app/serializers/analytics_merge_request_entity.rb b/app/serializers/analytics_merge_request_entity.rb
index 888265eaa38..b7134da9461 100644
--- a/app/serializers/analytics_merge_request_entity.rb
+++ b/app/serializers/analytics_merge_request_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsMergeRequestEntity < AnalyticsIssueEntity
   expose :state
 
diff --git a/app/serializers/analytics_merge_request_serializer.rb b/app/serializers/analytics_merge_request_serializer.rb
index 4622a1dd855..f0b9115d02c 100644
--- a/app/serializers/analytics_merge_request_serializer.rb
+++ b/app/serializers/analytics_merge_request_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsMergeRequestSerializer < AnalyticsGenericSerializer
   entity AnalyticsMergeRequestEntity
 end
diff --git a/app/serializers/analytics_stage_entity.rb b/app/serializers/analytics_stage_entity.rb
index 3e355a13e06..ae7c20c3bba 100644
--- a/app/serializers/analytics_stage_entity.rb
+++ b/app/serializers/analytics_stage_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsStageEntity < Grape::Entity
   include EntityDateHelper
 
diff --git a/app/serializers/analytics_stage_serializer.rb b/app/serializers/analytics_stage_serializer.rb
index 613cf6874d8..86786273240 100644
--- a/app/serializers/analytics_stage_serializer.rb
+++ b/app/serializers/analytics_stage_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsStageSerializer < BaseSerializer
   entity AnalyticsStageEntity
 end
diff --git a/app/serializers/analytics_summary_entity.rb b/app/serializers/analytics_summary_entity.rb
index 9c37afd53e1..39c6b4b06b2 100644
--- a/app/serializers/analytics_summary_entity.rb
+++ b/app/serializers/analytics_summary_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsSummaryEntity < Grape::Entity
   expose :value, safe: true
   expose :title
diff --git a/app/serializers/analytics_summary_serializer.rb b/app/serializers/analytics_summary_serializer.rb
index c87a24aa47c..b22bd737f03 100644
--- a/app/serializers/analytics_summary_serializer.rb
+++ b/app/serializers/analytics_summary_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnalyticsSummarySerializer < BaseSerializer
   entity AnalyticsSummaryEntity
 end
diff --git a/app/serializers/award_emoji_entity.rb b/app/serializers/award_emoji_entity.rb
index 6e03cd02392..212931a2fa9 100644
--- a/app/serializers/award_emoji_entity.rb
+++ b/app/serializers/award_emoji_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AwardEmojiEntity < Grape::Entity
   expose :name
   expose :user, using: API::Entities::UserSafe
diff --git a/app/serializers/base_serializer.rb b/app/serializers/base_serializer.rb
index 8cade280b0c..7b65bd22f54 100644
--- a/app/serializers/base_serializer.rb
+++ b/app/serializers/base_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BaseSerializer
   attr_reader :params
 
diff --git a/app/serializers/blob_entity.rb b/app/serializers/blob_entity.rb
index b501fd5e964..3ac61481dea 100644
--- a/app/serializers/blob_entity.rb
+++ b/app/serializers/blob_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BlobEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/build_action_entity.rb b/app/serializers/build_action_entity.rb
index f2d76a8ad81..f9da3f63911 100644
--- a/app/serializers/build_action_entity.rb
+++ b/app/serializers/build_action_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BuildActionEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/build_artifact_entity.rb b/app/serializers/build_artifact_entity.rb
index 6e0e33bc09b..414f436e76e 100644
--- a/app/serializers/build_artifact_entity.rb
+++ b/app/serializers/build_artifact_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BuildArtifactEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/build_details_entity.rb b/app/serializers/build_details_entity.rb
index 2de9624aed4..b887b99d31c 100644
--- a/app/serializers/build_details_entity.rb
+++ b/app/serializers/build_details_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BuildDetailsEntity < JobEntity
   expose :coverage, :erased_at, :duration
   expose :tag_list, as: :tags
diff --git a/app/serializers/build_metadata_entity.rb b/app/serializers/build_metadata_entity.rb
index f16f3badffa..6242ee8957d 100644
--- a/app/serializers/build_metadata_entity.rb
+++ b/app/serializers/build_metadata_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BuildMetadataEntity < Grape::Entity
   expose :timeout_human_readable
   expose :timeout_source do |metadata|
diff --git a/app/serializers/build_serializer.rb b/app/serializers/build_serializer.rb
index bae9932847f..0649fdad6a8 100644
--- a/app/serializers/build_serializer.rb
+++ b/app/serializers/build_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class BuildSerializer < BaseSerializer
   entity JobEntity
 
diff --git a/app/serializers/cluster_application_entity.rb b/app/serializers/cluster_application_entity.rb
index 77fc3336521..2bd17e58086 100644
--- a/app/serializers/cluster_application_entity.rb
+++ b/app/serializers/cluster_application_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ClusterApplicationEntity < Grape::Entity
   expose :name
   expose :status_name, as: :status
diff --git a/app/serializers/cluster_entity.rb b/app/serializers/cluster_entity.rb
index 7e5b0997878..c59f68bbc49 100644
--- a/app/serializers/cluster_entity.rb
+++ b/app/serializers/cluster_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ClusterEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/cluster_serializer.rb b/app/serializers/cluster_serializer.rb
index 2e13c1501e7..4bb4d4880d4 100644
--- a/app/serializers/cluster_serializer.rb
+++ b/app/serializers/cluster_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ClusterSerializer < BaseSerializer
   entity ClusterEntity
 
diff --git a/app/serializers/cohort_activity_month_entity.rb b/app/serializers/cohort_activity_month_entity.rb
index e6788a8b596..cdbc89a2dcd 100644
--- a/app/serializers/cohort_activity_month_entity.rb
+++ b/app/serializers/cohort_activity_month_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CohortActivityMonthEntity < Grape::Entity
   include ActionView::Helpers::NumberHelper
 
diff --git a/app/serializers/cohort_entity.rb b/app/serializers/cohort_entity.rb
index 7cdba5b0484..3d0213e1038 100644
--- a/app/serializers/cohort_entity.rb
+++ b/app/serializers/cohort_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CohortEntity < Grape::Entity
   include ActionView::Helpers::NumberHelper
 
diff --git a/app/serializers/cohorts_entity.rb b/app/serializers/cohorts_entity.rb
index 98f5995ba6f..a84d568bf30 100644
--- a/app/serializers/cohorts_entity.rb
+++ b/app/serializers/cohorts_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CohortsEntity < Grape::Entity
   expose :months_included
   expose :cohorts, using: CohortEntity
diff --git a/app/serializers/cohorts_serializer.rb b/app/serializers/cohorts_serializer.rb
index fe9367b13d8..ceca5e1e5a8 100644
--- a/app/serializers/cohorts_serializer.rb
+++ b/app/serializers/cohorts_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CohortsSerializer < AnalyticsGenericSerializer
   entity CohortsEntity
 end
diff --git a/app/serializers/commit_entity.rb b/app/serializers/commit_entity.rb
index c8dd98cc04d..b3287c66554 100644
--- a/app/serializers/commit_entity.rb
+++ b/app/serializers/commit_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CommitEntity < API::Entities::Commit
   include RequestAwareEntity
 
diff --git a/app/serializers/concerns/with_pagination.rb b/app/serializers/concerns/with_pagination.rb
index 89631b73fcf..c8ffae355e8 100644
--- a/app/serializers/concerns/with_pagination.rb
+++ b/app/serializers/concerns/with_pagination.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module WithPagination
   attr_accessor :paginator
 
diff --git a/app/serializers/container_repositories_serializer.rb b/app/serializers/container_repositories_serializer.rb
index 56dc70b5687..e1ce3c7b3ae 100644
--- a/app/serializers/container_repositories_serializer.rb
+++ b/app/serializers/container_repositories_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ContainerRepositoriesSerializer < BaseSerializer
   entity ContainerRepositoryEntity
 end
diff --git a/app/serializers/container_repository_entity.rb b/app/serializers/container_repository_entity.rb
index 1103cf30a07..59bf35f5aff 100644
--- a/app/serializers/container_repository_entity.rb
+++ b/app/serializers/container_repository_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ContainerRepositoryEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/container_tag_entity.rb b/app/serializers/container_tag_entity.rb
index 8f1488e6cbb..637294877f8 100644
--- a/app/serializers/container_tag_entity.rb
+++ b/app/serializers/container_tag_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ContainerTagEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/container_tags_serializer.rb b/app/serializers/container_tags_serializer.rb
index 6ff3adff135..982ce33f6e3 100644
--- a/app/serializers/container_tags_serializer.rb
+++ b/app/serializers/container_tags_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ContainerTagsSerializer < BaseSerializer
   entity ContainerTagEntity
 
diff --git a/app/serializers/deploy_key_entity.rb b/app/serializers/deploy_key_entity.rb
index 2678f99510c..54bf030aba1 100644
--- a/app/serializers/deploy_key_entity.rb
+++ b/app/serializers/deploy_key_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DeployKeyEntity < Grape::Entity
   expose :id
   expose :user_id
diff --git a/app/serializers/deploy_key_serializer.rb b/app/serializers/deploy_key_serializer.rb
index 8f849eb88b7..a1cd98b631b 100644
--- a/app/serializers/deploy_key_serializer.rb
+++ b/app/serializers/deploy_key_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DeployKeySerializer < BaseSerializer
   entity DeployKeyEntity
 end
diff --git a/app/serializers/deploy_keys_project_entity.rb b/app/serializers/deploy_keys_project_entity.rb
index 568ef5ab75e..5775ad72d0d 100644
--- a/app/serializers/deploy_keys_project_entity.rb
+++ b/app/serializers/deploy_keys_project_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DeployKeysProjectEntity < Grape::Entity
   expose :can_push
   expose :project, using: ProjectEntity
diff --git a/app/serializers/deployment_entity.rb b/app/serializers/deployment_entity.rb
index 241c689bccd..344148a1fb7 100644
--- a/app/serializers/deployment_entity.rb
+++ b/app/serializers/deployment_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DeploymentEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/deployment_serializer.rb b/app/serializers/deployment_serializer.rb
index cba5c3f311f..04db6b88489 100644
--- a/app/serializers/deployment_serializer.rb
+++ b/app/serializers/deployment_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DeploymentSerializer < BaseSerializer
   entity DeploymentEntity
 
diff --git a/app/serializers/diff_file_entity.rb b/app/serializers/diff_file_entity.rb
index 61135fba97b..79844c9210a 100644
--- a/app/serializers/diff_file_entity.rb
+++ b/app/serializers/diff_file_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DiffFileEntity < Grape::Entity
   include RequestAwareEntity
   include BlobHelper
diff --git a/app/serializers/diffs_entity.rb b/app/serializers/diffs_entity.rb
index bb804e5347a..f75ace14d9c 100644
--- a/app/serializers/diffs_entity.rb
+++ b/app/serializers/diffs_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DiffsEntity < Grape::Entity
   include DiffHelper
   include RequestAwareEntity
diff --git a/app/serializers/diffs_serializer.rb b/app/serializers/diffs_serializer.rb
index 6771e10c5ac..9e5eb1699d4 100644
--- a/app/serializers/diffs_serializer.rb
+++ b/app/serializers/diffs_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DiffsSerializer < BaseSerializer
   entity DiffsEntity
 end
diff --git a/app/serializers/discussion_entity.rb b/app/serializers/discussion_entity.rb
index 7505bbdeb3d..6f95e6f9ca1 100644
--- a/app/serializers/discussion_entity.rb
+++ b/app/serializers/discussion_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DiscussionEntity < Grape::Entity
   include RequestAwareEntity
   include NotesHelper
diff --git a/app/serializers/discussion_serializer.rb b/app/serializers/discussion_serializer.rb
index ed5e1224bb2..5be40e74175 100644
--- a/app/serializers/discussion_serializer.rb
+++ b/app/serializers/discussion_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DiscussionSerializer < BaseSerializer
   entity DiscussionEntity
 end
diff --git a/app/serializers/entity_date_helper.rb b/app/serializers/entity_date_helper.rb
index 464217123b4..cc0c2abf863 100644
--- a/app/serializers/entity_date_helper.rb
+++ b/app/serializers/entity_date_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module EntityDateHelper
   include ActionView::Helpers::DateHelper
   include ActionView::Helpers::TagHelper
@@ -50,15 +52,20 @@ module EntityDateHelper
     elsif entity.due_date
       is_upcoming = (entity.due_date - Date.today).to_i > 0
       time_ago = time_ago_in_words(entity.due_date)
-      content = time_ago.gsub(/\d+/) { |match| "<strong>#{match}</strong>" }
-      content.slice!("about ")
-      content << " " + (is_upcoming ? _("remaining") : _("ago"))
-      content.html_safe
+
+      # https://gitlab.com/gitlab-org/gitlab-ce/issues/49440
+      #
+      # Need to improve the i18n here and do a full translation
+      # of the string instead of piecewise translations.
+      content = time_ago
+        .gsub(/\d+/) { |match| "<strong>#{match}</strong>" }
+        .remove("about ")
+      remaining_or_ago = is_upcoming ? _("remaining") : _("ago")
+
+      "#{content} #{remaining_or_ago}".html_safe
     elsif entity.start_date && entity.start_date.past?
-      days    = entity.elapsed_days
-      content = content_tag(:strong, days)
-      content << " #{'day'.pluralize(days)} elapsed"
-      content.html_safe
+      days = entity.elapsed_days
+      "#{content_tag(:strong, days)} #{'day'.pluralize(days)} elapsed".html_safe
     end
   end
 end
diff --git a/app/serializers/entity_request.rb b/app/serializers/entity_request.rb
index 456ba1174c0..49e026e8c2a 100644
--- a/app/serializers/entity_request.rb
+++ b/app/serializers/entity_request.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class EntityRequest
   # We use EntityRequest object to collect parameters and variables
   # from the controller. Because options that are being passed to the entity
diff --git a/app/serializers/environment_entity.rb b/app/serializers/environment_entity.rb
index 83558fc6659..b18e9706db6 100644
--- a/app/serializers/environment_entity.rb
+++ b/app/serializers/environment_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class EnvironmentEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/environment_serializer.rb b/app/serializers/environment_serializer.rb
index 84722f33f59..dc1686c30c4 100644
--- a/app/serializers/environment_serializer.rb
+++ b/app/serializers/environment_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class EnvironmentSerializer < BaseSerializer
   include WithPagination
 
diff --git a/app/serializers/group_child_entity.rb b/app/serializers/group_child_entity.rb
index ee150eefd9e..f6804fe7f6a 100644
--- a/app/serializers/group_child_entity.rb
+++ b/app/serializers/group_child_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupChildEntity < Grape::Entity
   include ActionView::Helpers::NumberHelper
   include RequestAwareEntity
diff --git a/app/serializers/group_child_serializer.rb b/app/serializers/group_child_serializer.rb
index 2baef0a5703..789707c2c9b 100644
--- a/app/serializers/group_child_serializer.rb
+++ b/app/serializers/group_child_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupChildSerializer < BaseSerializer
   include WithPagination
 
diff --git a/app/serializers/group_entity.rb b/app/serializers/group_entity.rb
index 6d8466da902..c46c342ee5d 100644
--- a/app/serializers/group_entity.rb
+++ b/app/serializers/group_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupEntity < Grape::Entity
   include ActionView::Helpers::NumberHelper
   include RequestAwareEntity
diff --git a/app/serializers/group_serializer.rb b/app/serializers/group_serializer.rb
index 8cf7eb63bcf..38c5757a6c1 100644
--- a/app/serializers/group_serializer.rb
+++ b/app/serializers/group_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupSerializer < BaseSerializer
   include WithPagination
 
diff --git a/app/serializers/group_variable_entity.rb b/app/serializers/group_variable_entity.rb
index 62cf0b21e1e..0edab4a3092 100644
--- a/app/serializers/group_variable_entity.rb
+++ b/app/serializers/group_variable_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupVariableEntity < Grape::Entity
   expose :id
   expose :key
diff --git a/app/serializers/group_variable_serializer.rb b/app/serializers/group_variable_serializer.rb
index 8f8205924aa..ed20b240cce 100644
--- a/app/serializers/group_variable_serializer.rb
+++ b/app/serializers/group_variable_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GroupVariableSerializer < BaseSerializer
   entity GroupVariableEntity
 end
diff --git a/app/serializers/issuable_entity.rb b/app/serializers/issuable_entity.rb
index 6f31fbd6b7c..e71bd3313fb 100644
--- a/app/serializers/issuable_entity.rb
+++ b/app/serializers/issuable_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class IssuableEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/issuable_sidebar_entity.rb b/app/serializers/issuable_sidebar_entity.rb
index 29138c803df..773d78d324c 100644
--- a/app/serializers/issuable_sidebar_entity.rb
+++ b/app/serializers/issuable_sidebar_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class IssuableSidebarEntity < Grape::Entity
   include TimeTrackableEntity
   include RequestAwareEntity
diff --git a/app/serializers/issue_entity.rb b/app/serializers/issue_entity.rb
index 840fdbcbf14..16a477c92fa 100644
--- a/app/serializers/issue_entity.rb
+++ b/app/serializers/issue_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class IssueEntity < IssuableEntity
   include TimeTrackableEntity
 
diff --git a/app/serializers/issue_serializer.rb b/app/serializers/issue_serializer.rb
index 2555595379b..37cf5e28396 100644
--- a/app/serializers/issue_serializer.rb
+++ b/app/serializers/issue_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class IssueSerializer < BaseSerializer
   # This overrided method takes care of which entity should be used
   # to serialize the `issue` based on `basic` key in `opts` param.
diff --git a/app/serializers/issue_sidebar_entity.rb b/app/serializers/issue_sidebar_entity.rb
index 6c823dbfe95..349ad9d1fef 100644
--- a/app/serializers/issue_sidebar_entity.rb
+++ b/app/serializers/issue_sidebar_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class IssueSidebarEntity < IssuableSidebarEntity
   expose :assignees, using: API::Entities::UserBasic
 end
diff --git a/app/serializers/job_entity.rb b/app/serializers/job_entity.rb
index 960e7291ae6..7bc1d87dea5 100644
--- a/app/serializers/job_entity.rb
+++ b/app/serializers/job_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class JobEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/job_group_entity.rb b/app/serializers/job_group_entity.rb
index 8554de55517..0941a9d36be 100644
--- a/app/serializers/job_group_entity.rb
+++ b/app/serializers/job_group_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class JobGroupEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/label_entity.rb b/app/serializers/label_entity.rb
index 4452161051e..98743d62b50 100644
--- a/app/serializers/label_entity.rb
+++ b/app/serializers/label_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LabelEntity < Grape::Entity
   expose :id, if: ->(label, _) { !label.is_a?(GlobalLabel) }
 
diff --git a/app/serializers/label_serializer.rb b/app/serializers/label_serializer.rb
index ad6ba8c46c9..25b9f7de243 100644
--- a/app/serializers/label_serializer.rb
+++ b/app/serializers/label_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LabelSerializer < BaseSerializer
   entity LabelEntity
 
diff --git a/app/serializers/lfs_file_lock_entity.rb b/app/serializers/lfs_file_lock_entity.rb
index 264a77adc3f..7961c4e666b 100644
--- a/app/serializers/lfs_file_lock_entity.rb
+++ b/app/serializers/lfs_file_lock_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LfsFileLockEntity < Grape::Entity
   root 'locks', 'lock'
 
diff --git a/app/serializers/lfs_file_lock_serializer.rb b/app/serializers/lfs_file_lock_serializer.rb
index ba8fb1a461d..0367097e376 100644
--- a/app/serializers/lfs_file_lock_serializer.rb
+++ b/app/serializers/lfs_file_lock_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LfsFileLockSerializer < BaseSerializer
   entity LfsFileLockEntity
 end
diff --git a/app/serializers/merge_request_basic_entity.rb b/app/serializers/merge_request_basic_entity.rb
index 1c06691026d..f7eb74cf392 100644
--- a/app/serializers/merge_request_basic_entity.rb
+++ b/app/serializers/merge_request_basic_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestBasicEntity < IssuableSidebarEntity
   expose :assignee_id
   expose :merge_status
diff --git a/app/serializers/merge_request_basic_serializer.rb b/app/serializers/merge_request_basic_serializer.rb
index cc5c664c8fa..a68b48b00db 100644
--- a/app/serializers/merge_request_basic_serializer.rb
+++ b/app/serializers/merge_request_basic_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestBasicSerializer < BaseSerializer
   entity MergeRequestBasicEntity
 end
diff --git a/app/serializers/merge_request_create_entity.rb b/app/serializers/merge_request_create_entity.rb
index 11234313293..e7a93004dda 100644
--- a/app/serializers/merge_request_create_entity.rb
+++ b/app/serializers/merge_request_create_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestCreateEntity < Grape::Entity
   expose :iid
 
diff --git a/app/serializers/merge_request_create_serializer.rb b/app/serializers/merge_request_create_serializer.rb
index 08daf473319..b6df9ee13fc 100644
--- a/app/serializers/merge_request_create_serializer.rb
+++ b/app/serializers/merge_request_create_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestCreateSerializer < BaseSerializer
   entity MergeRequestCreateEntity
 end
diff --git a/app/serializers/merge_request_diff_entity.rb b/app/serializers/merge_request_diff_entity.rb
index 32c761b45ac..433bfe60474 100644
--- a/app/serializers/merge_request_diff_entity.rb
+++ b/app/serializers/merge_request_diff_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestDiffEntity < Grape::Entity
   include Gitlab::Routing
   include GitHelper
diff --git a/app/serializers/merge_request_metrics_entity.rb b/app/serializers/merge_request_metrics_entity.rb
index 3548107ac16..1c9db08d103 100644
--- a/app/serializers/merge_request_metrics_entity.rb
+++ b/app/serializers/merge_request_metrics_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestMetricsEntity < Grape::Entity
   expose :latest_closed_at, as: :closed_at
   expose :merged_at
diff --git a/app/serializers/merge_request_serializer.rb b/app/serializers/merge_request_serializer.rb
index caf193bdae3..1f8c830e1aa 100644
--- a/app/serializers/merge_request_serializer.rb
+++ b/app/serializers/merge_request_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestSerializer < BaseSerializer
   # This overrided method takes care of which entity should be used
   # to serialize the `merge_request` based on `serializer` key in `opts` param.
diff --git a/app/serializers/merge_request_user_entity.rb b/app/serializers/merge_request_user_entity.rb
index 33fc7b724d5..fd2d2897113 100644
--- a/app/serializers/merge_request_user_entity.rb
+++ b/app/serializers/merge_request_user_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestUserEntity < UserEntity
   include RequestAwareEntity
   include BlobHelper
diff --git a/app/serializers/merge_request_widget_entity.rb b/app/serializers/merge_request_widget_entity.rb
index a78bd77cf7c..4fe04e4b206 100644
--- a/app/serializers/merge_request_widget_entity.rb
+++ b/app/serializers/merge_request_widget_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MergeRequestWidgetEntity < IssuableEntity
   expose :state
   expose :in_progress_merge_commit_sha
diff --git a/app/serializers/note_attachment_entity.rb b/app/serializers/note_attachment_entity.rb
index 1ad50568ab9..dc801e2bf4e 100644
--- a/app/serializers/note_attachment_entity.rb
+++ b/app/serializers/note_attachment_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class NoteAttachmentEntity < Grape::Entity
   expose :url
   expose :filename
diff --git a/app/serializers/note_entity.rb b/app/serializers/note_entity.rb
index 0e1f94a9f61..daa5c24d0f5 100644
--- a/app/serializers/note_entity.rb
+++ b/app/serializers/note_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class NoteEntity < API::Entities::Note
   include RequestAwareEntity
   include NotesHelper
diff --git a/app/serializers/note_user_entity.rb b/app/serializers/note_user_entity.rb
index 7289f3a0222..b00dfa7d353 100644
--- a/app/serializers/note_user_entity.rb
+++ b/app/serializers/note_user_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class NoteUserEntity < UserEntity
   unexpose :web_url
 end
diff --git a/app/serializers/pipeline_details_entity.rb b/app/serializers/pipeline_details_entity.rb
index 8ba9cac53c4..3b56767f774 100644
--- a/app/serializers/pipeline_details_entity.rb
+++ b/app/serializers/pipeline_details_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PipelineDetailsEntity < PipelineEntity
   expose :details do
     expose :ordered_stages, as: :stages, using: StageEntity
diff --git a/app/serializers/pipeline_entity.rb b/app/serializers/pipeline_entity.rb
index f782b411b84..6cf1925adda 100644
--- a/app/serializers/pipeline_entity.rb
+++ b/app/serializers/pipeline_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PipelineEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/pipeline_serializer.rb b/app/serializers/pipeline_serializer.rb
index 17a022539bb..4a33160afa1 100644
--- a/app/serializers/pipeline_serializer.rb
+++ b/app/serializers/pipeline_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PipelineSerializer < BaseSerializer
   include WithPagination
   entity PipelineDetailsEntity
diff --git a/app/serializers/project_entity.rb b/app/serializers/project_entity.rb
index b3e5fd21e97..60c4ba135d6 100644
--- a/app/serializers/project_entity.rb
+++ b/app/serializers/project_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProjectEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/project_mirror_entity.rb b/app/serializers/project_mirror_entity.rb
index a9c08ac021a..8aba244cd11 100644
--- a/app/serializers/project_mirror_entity.rb
+++ b/app/serializers/project_mirror_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProjectMirrorEntity < Grape::Entity
   expose :id
 
diff --git a/app/serializers/project_note_entity.rb b/app/serializers/project_note_entity.rb
index e541bfbee8d..d7c4d0aacc6 100644
--- a/app/serializers/project_note_entity.rb
+++ b/app/serializers/project_note_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProjectNoteEntity < NoteEntity
   expose :human_access do |note|
     note.project.team.human_max_access(note.author_id)
diff --git a/app/serializers/project_note_serializer.rb b/app/serializers/project_note_serializer.rb
index 763ad0bdb3f..2182904e815 100644
--- a/app/serializers/project_note_serializer.rb
+++ b/app/serializers/project_note_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProjectNoteSerializer < BaseSerializer
   entity ProjectNoteEntity
 end
diff --git a/app/serializers/project_serializer.rb b/app/serializers/project_serializer.rb
index 74de1e79a8f..23b96c2fc9e 100644
--- a/app/serializers/project_serializer.rb
+++ b/app/serializers/project_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProjectSerializer < BaseSerializer
   entity ProjectEntity
 end
diff --git a/app/serializers/request_aware_entity.rb b/app/serializers/request_aware_entity.rb
index d53fcfb8c1b..1524c1291d8 100644
--- a/app/serializers/request_aware_entity.rb
+++ b/app/serializers/request_aware_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module RequestAwareEntity
   extend ActiveSupport::Concern
 
diff --git a/app/serializers/runner_entity.rb b/app/serializers/runner_entity.rb
index db26eadab2d..04ec80e0efa 100644
--- a/app/serializers/runner_entity.rb
+++ b/app/serializers/runner_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RunnerEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/stage_entity.rb b/app/serializers/stage_entity.rb
index 2516df70ad9..00e6d32ee3a 100644
--- a/app/serializers/stage_entity.rb
+++ b/app/serializers/stage_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StageEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/stage_serializer.rb b/app/serializers/stage_serializer.rb
index 091d8e91e43..11fb0d3f852 100644
--- a/app/serializers/stage_serializer.rb
+++ b/app/serializers/stage_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StageSerializer < BaseSerializer
   include WithPagination
 
diff --git a/app/serializers/status_entity.rb b/app/serializers/status_entity.rb
index 47df7f9dcf9..306c30f0323 100644
--- a/app/serializers/status_entity.rb
+++ b/app/serializers/status_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StatusEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/submodule_entity.rb b/app/serializers/submodule_entity.rb
index ed1f1ae0ef0..e475a4f301f 100644
--- a/app/serializers/submodule_entity.rb
+++ b/app/serializers/submodule_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SubmoduleEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/time_trackable_entity.rb b/app/serializers/time_trackable_entity.rb
index e81cd7bec72..613d19703a4 100644
--- a/app/serializers/time_trackable_entity.rb
+++ b/app/serializers/time_trackable_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module TimeTrackableEntity
   extend ActiveSupport::Concern
   extend Grape
diff --git a/app/serializers/tree_entity.rb b/app/serializers/tree_entity.rb
index 9f1b485347f..9b7dc80e1d9 100644
--- a/app/serializers/tree_entity.rb
+++ b/app/serializers/tree_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TreeEntity < Grape::Entity
   include RequestAwareEntity
 
diff --git a/app/serializers/tree_root_entity.rb b/app/serializers/tree_root_entity.rb
index 496f070ddbd..f1cfcd943d8 100644
--- a/app/serializers/tree_root_entity.rb
+++ b/app/serializers/tree_root_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # TODO: Inherit from TreeEntity, when `Tree` implements `id` and `name` like `Gitlab::Git::Tree`.
 class TreeRootEntity < Grape::Entity
   include RequestAwareEntity
diff --git a/app/serializers/tree_serializer.rb b/app/serializers/tree_serializer.rb
index 713ade23bc9..536b8ab1ae2 100644
--- a/app/serializers/tree_serializer.rb
+++ b/app/serializers/tree_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TreeSerializer < BaseSerializer
   entity TreeRootEntity
 end
diff --git a/app/serializers/user_entity.rb b/app/serializers/user_entity.rb
index 876512b12dc..6236d66ff4a 100644
--- a/app/serializers/user_entity.rb
+++ b/app/serializers/user_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UserEntity < API::Entities::UserBasic
   include RequestAwareEntity
 
diff --git a/app/serializers/user_serializer.rb b/app/serializers/user_serializer.rb
index 49a71ebac61..2111e1b5667 100644
--- a/app/serializers/user_serializer.rb
+++ b/app/serializers/user_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UserSerializer < BaseSerializer
   entity UserEntity
 end
diff --git a/app/serializers/variable_entity.rb b/app/serializers/variable_entity.rb
index d576745c073..85cf367fe51 100644
--- a/app/serializers/variable_entity.rb
+++ b/app/serializers/variable_entity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class VariableEntity < Grape::Entity
   expose :id
   expose :key
diff --git a/app/serializers/variable_serializer.rb b/app/serializers/variable_serializer.rb
index 32ae82ab51c..586666cad8e 100644
--- a/app/serializers/variable_serializer.rb
+++ b/app/serializers/variable_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class VariableSerializer < BaseSerializer
   entity VariableEntity
 end
diff --git a/changelogs/unreleased/frozen-string-enable-app-serializers.yml b/changelogs/unreleased/frozen-string-enable-app-serializers.yml
new file mode 100644
index 00000000000..40c7b695d39
--- /dev/null
+++ b/changelogs/unreleased/frozen-string-enable-app-serializers.yml
@@ -0,0 +1,5 @@
+---
+title: Enable frozen string in app/serializers/**/*.rb
+merge_request: 20726
+author: gfyoung
+type: performance