Enable frozen string in lib/api and lib/backup

Partially addresses #47424.

Had to make changes to spec files because
stubbing methods on frozen objects is a mess
in RSpec and leads to failures:

https://github.com/rspec/rspec-mocks/issues/1190

89 files changed, 180 insertions, 1 deletions

diff --git a/lib/api/access_requests.rb b/lib/api/access_requests.rb
index 18063fb20a2..cecff6d3b81 100644
--- a/lib/api/access_requests.rb
+++ b/lib/api/access_requests.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class AccessRequests < Grape::API
     include PaginationParams
diff --git a/lib/api/api.rb b/lib/api/api.rb
index e89d9337853..06c8b48b8cc 100644
--- a/lib/api/api.rb
+++ b/lib/api/api.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class API < Grape::API
     include APIGuard
diff --git a/lib/api/api_guard.rb b/lib/api/api_guard.rb
index 8ee7987cfff..61357b3f1d6 100644
--- a/lib/api/api_guard.rb
+++ b/lib/api/api_guard.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Guard API with OAuth 2.0 Access Token
 
 require 'rack/oauth2'
diff --git a/lib/api/applications.rb b/lib/api/applications.rb
index b122cdefe4e..f29cd7fc003 100644
--- a/lib/api/applications.rb
+++ b/lib/api/applications.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # External applications API
   class Applications < Grape::API
diff --git a/lib/api/avatar.rb b/lib/api/avatar.rb
index 70219bc8ea0..0f14d003065 100644
--- a/lib/api/avatar.rb
+++ b/lib/api/avatar.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Avatar < Grape::API
     resource :avatar do
diff --git a/lib/api/award_emoji.rb b/lib/api/award_emoji.rb
index e334af22183..c2abf9155f3 100644
--- a/lib/api/award_emoji.rb
+++ b/lib/api/award_emoji.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class AwardEmoji < Grape::API
     include PaginationParams
diff --git a/lib/api/badges.rb b/lib/api/badges.rb
index 8ceffe9c5ef..ab670988f47 100644
--- a/lib/api/badges.rb
+++ b/lib/api/badges.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Badges < Grape::API
     include PaginationParams
diff --git a/lib/api/boards.rb b/lib/api/boards.rb
index 0f89414148b..c80e1c57864 100644
--- a/lib/api/boards.rb
+++ b/lib/api/boards.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Boards < Grape::API
     include BoardsResponses
diff --git a/lib/api/boards_responses.rb b/lib/api/boards_responses.rb
index 3322b37c6ff..86d9b24802f 100644
--- a/lib/api/boards_responses.rb
+++ b/lib/api/boards_responses.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module BoardsResponses
     extend ActiveSupport::Concern
diff --git a/lib/api/branches.rb b/lib/api/branches.rb
index 5d106ed93a0..2735d410c8e 100644
--- a/lib/api/branches.rb
+++ b/lib/api/branches.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mime/types'
 
 module API
diff --git a/lib/api/broadcast_messages.rb b/lib/api/broadcast_messages.rb
index d7138b2f2fe..19148758fc5 100644
--- a/lib/api/broadcast_messages.rb
+++ b/lib/api/broadcast_messages.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class BroadcastMessages < Grape::API
     include PaginationParams
diff --git a/lib/api/circuit_breakers.rb b/lib/api/circuit_breakers.rb
index c13154dc0ec..6eddc5e5b61 100644
--- a/lib/api/circuit_breakers.rb
+++ b/lib/api/circuit_breakers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class CircuitBreakers < Grape::API
     before { authenticated_as_admin! }
diff --git a/lib/api/commit_statuses.rb b/lib/api/commit_statuses.rb
index 8e6f706afd4..99553d993ca 100644
--- a/lib/api/commit_statuses.rb
+++ b/lib/api/commit_statuses.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mime/types'
 
 module API
diff --git a/lib/api/commits.rb b/lib/api/commits.rb
index 5aeffc8fb99..f0db1318146 100644
--- a/lib/api/commits.rb
+++ b/lib/api/commits.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mime/types'
 
 module API
diff --git a/lib/api/custom_attributes_endpoints.rb b/lib/api/custom_attributes_endpoints.rb
index b5864665cc3..2149e04451e 100644
--- a/lib/api/custom_attributes_endpoints.rb
+++ b/lib/api/custom_attributes_endpoints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module CustomAttributesEndpoints
     extend ActiveSupport::Concern
diff --git a/lib/api/deploy_keys.rb b/lib/api/deploy_keys.rb
index 501e9f64db0..ce35720d408 100644
--- a/lib/api/deploy_keys.rb
+++ b/lib/api/deploy_keys.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class DeployKeys < Grape::API
     include PaginationParams
diff --git a/lib/api/deployments.rb b/lib/api/deployments.rb
index b7892599295..6747e2e5005 100644
--- a/lib/api/deployments.rb
+++ b/lib/api/deployments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Deployments RESTful API endpoints
   class Deployments < Grape::API
diff --git a/lib/api/discussions.rb b/lib/api/discussions.rb
index 88668992215..39c6d28391d 100644
--- a/lib/api/discussions.rb
+++ b/lib/api/discussions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Discussions < Grape::API
     include PaginationParams
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 12c4340c1ba..a78a93cbfd9 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Entities
     class WikiPageBasic < Grape::Entity
diff --git a/lib/api/environments.rb b/lib/api/environments.rb
index fa828f43001..c64217a6977 100644
--- a/lib/api/environments.rb
+++ b/lib/api/environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Environments RESTfull API endpoints
   class Environments < Grape::API
diff --git a/lib/api/events.rb b/lib/api/events.rb
index dfe0e81af26..bca4db1a80e 100644
--- a/lib/api/events.rb
+++ b/lib/api/events.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Events < Grape::API
     include PaginationParams
diff --git a/lib/api/features.rb b/lib/api/features.rb
index 79be8c1903e..6f2422af13a 100644
--- a/lib/api/features.rb
+++ b/lib/api/features.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Features < Grape::API
     before { authenticated_as_admin! }
diff --git a/lib/api/files.rb b/lib/api/files.rb
index ac02488d30c..bcd2cd48a45 100644
--- a/lib/api/files.rb
+++ b/lib/api/files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Files < Grape::API
     FILE_ENDPOINT_REQUIREMENTS = API::PROJECT_ENDPOINT_REQUIREMENTS.merge(file_path: API::NO_SLASH_URL_PART_REGEX)
diff --git a/lib/api/group_boards.rb b/lib/api/group_boards.rb
index 3832cdc10a8..dc30e868e2e 100644
--- a/lib/api/group_boards.rb
+++ b/lib/api/group_boards.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class GroupBoards < Grape::API
     include BoardsResponses
diff --git a/lib/api/group_milestones.rb b/lib/api/group_milestones.rb
index 4b4352c2b27..b36436dbf43 100644
--- a/lib/api/group_milestones.rb
+++ b/lib/api/group_milestones.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class GroupMilestones < Grape::API
     include MilestoneResponses
diff --git a/lib/api/group_variables.rb b/lib/api/group_variables.rb
index b6610dd04b3..ae7241e9a30 100644
--- a/lib/api/group_variables.rb
+++ b/lib/api/group_variables.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class GroupVariables < Grape::API
     include PaginationParams
diff --git a/lib/api/groups.rb b/lib/api/groups.rb
index 018ca72c32a..64b998ab455 100644
--- a/lib/api/groups.rb
+++ b/lib/api/groups.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Groups < Grape::API
     include PaginationParams
diff --git a/lib/api/helpers.rb b/lib/api/helpers.rb
index 85e3e06e4fd..a7ba8066233 100644
--- a/lib/api/helpers.rb
+++ b/lib/api/helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     include Gitlab::Utils
@@ -381,9 +383,10 @@ module API
       # lifted from https://github.com/rails/rails/blob/master/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb#L60
       trace = exception.backtrace
 
-      message = "\n#{exception.class} (#{exception.message}):\n"
+      message = ["\n#{exception.class} (#{exception.message}):\n"]
       message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
       message << "  " << trace.join("\n  ")
+      message = message.join
 
       API.logger.add Logger::FATAL, message
 
diff --git a/lib/api/helpers/badges_helpers.rb b/lib/api/helpers/badges_helpers.rb
index 1f8afbf3c90..46ce5b4e7b5 100644
--- a/lib/api/helpers/badges_helpers.rb
+++ b/lib/api/helpers/badges_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module BadgesHelpers
diff --git a/lib/api/helpers/common_helpers.rb b/lib/api/helpers/common_helpers.rb
index 9993caa5249..7551ca50a7f 100644
--- a/lib/api/helpers/common_helpers.rb
+++ b/lib/api/helpers/common_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module CommonHelpers
diff --git a/lib/api/helpers/custom_attributes.rb b/lib/api/helpers/custom_attributes.rb
index 3bbe827967e..88208226c40 100644
--- a/lib/api/helpers/custom_attributes.rb
+++ b/lib/api/helpers/custom_attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module CustomAttributes
diff --git a/lib/api/helpers/custom_validators.rb b/lib/api/helpers/custom_validators.rb
index dd4f6c41131..23b1cd1ad45 100644
--- a/lib/api/helpers/custom_validators.rb
+++ b/lib/api/helpers/custom_validators.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module CustomValidators
diff --git a/lib/api/helpers/headers_helpers.rb b/lib/api/helpers/headers_helpers.rb
index c9c44e3c218..7553af9d156 100644
--- a/lib/api/helpers/headers_helpers.rb
+++ b/lib/api/helpers/headers_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module HeadersHelpers
diff --git a/lib/api/helpers/internal_helpers.rb b/lib/api/helpers/internal_helpers.rb
index 83151be82ad..4eaaca96b49 100644
--- a/lib/api/helpers/internal_helpers.rb
+++ b/lib/api/helpers/internal_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module InternalHelpers
diff --git a/lib/api/helpers/members_helpers.rb b/lib/api/helpers/members_helpers.rb
index 518aaa62aef..73d58ee7f37 100644
--- a/lib/api/helpers/members_helpers.rb
+++ b/lib/api/helpers/members_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # rubocop:disable GitlabSecurity/PublicSend
 
 module API
diff --git a/lib/api/helpers/notes_helpers.rb b/lib/api/helpers/notes_helpers.rb
index 7b1f5c2584b..216b2c45741 100644
--- a/lib/api/helpers/notes_helpers.rb
+++ b/lib/api/helpers/notes_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module NotesHelpers
diff --git a/lib/api/helpers/pagination.rb b/lib/api/helpers/pagination.rb
index 50bcd4e0437..d311cbb5f7e 100644
--- a/lib/api/helpers/pagination.rb
+++ b/lib/api/helpers/pagination.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module Pagination
diff --git a/lib/api/helpers/project_snapshots_helpers.rb b/lib/api/helpers/project_snapshots_helpers.rb
index 94798a8cb51..1b5dc281e38 100644
--- a/lib/api/helpers/project_snapshots_helpers.rb
+++ b/lib/api/helpers/project_snapshots_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module ProjectSnapshotsHelpers
diff --git a/lib/api/helpers/projects_helpers.rb b/lib/api/helpers/projects_helpers.rb
index 98672f2f765..e6a72b949f9 100644
--- a/lib/api/helpers/projects_helpers.rb
+++ b/lib/api/helpers/projects_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module ProjectsHelpers
diff --git a/lib/api/helpers/related_resources_helpers.rb b/lib/api/helpers/related_resources_helpers.rb
index bc7333ca4b3..793ae11b41d 100644
--- a/lib/api/helpers/related_resources_helpers.rb
+++ b/lib/api/helpers/related_resources_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module RelatedResourcesHelpers
diff --git a/lib/api/helpers/runner.rb b/lib/api/helpers/runner.rb
index 61eb88d3331..45d0343bc89 100644
--- a/lib/api/helpers/runner.rb
+++ b/lib/api/helpers/runner.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module Helpers
     module Runner
diff --git a/lib/api/internal.rb b/lib/api/internal.rb
index 71b87f60bf6..6a264c4cc6d 100644
--- a/lib/api/internal.rb
+++ b/lib/api/internal.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Internal access API
   class Internal < Grape::API
diff --git a/lib/api/issues.rb b/lib/api/issues.rb
index bcb03a0b540..25d78053c88 100644
--- a/lib/api/issues.rb
+++ b/lib/api/issues.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Issues < Grape::API
     include PaginationParams
diff --git a/lib/api/job_artifacts.rb b/lib/api/job_artifacts.rb
index ab4203c4e25..2229cbcd9d4 100644
--- a/lib/api/job_artifacts.rb
+++ b/lib/api/job_artifacts.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class JobArtifacts < Grape::API
     before { authenticate_non_get! }
diff --git a/lib/api/jobs.rb b/lib/api/jobs.rb
index 27ffd42834c..63fab6b0abb 100644
--- a/lib/api/jobs.rb
+++ b/lib/api/jobs.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Jobs < Grape::API
     include PaginationParams
diff --git a/lib/api/keys.rb b/lib/api/keys.rb
index fd93f797f72..d5280a0035d 100644
--- a/lib/api/keys.rb
+++ b/lib/api/keys.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Keys API
   class Keys < Grape::API
diff --git a/lib/api/labels.rb b/lib/api/labels.rb
index 98c9818db39..28555454307 100644
--- a/lib/api/labels.rb
+++ b/lib/api/labels.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Labels < Grape::API
     include PaginationParams
diff --git a/lib/api/lint.rb b/lib/api/lint.rb
index d202eaa4c49..0342a4b6654 100644
--- a/lib/api/lint.rb
+++ b/lib/api/lint.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Lint < Grape::API
     namespace :ci do
diff --git a/lib/api/markdown.rb b/lib/api/markdown.rb
index 5d55224c1a7..50d8a1ac596 100644
--- a/lib/api/markdown.rb
+++ b/lib/api/markdown.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Markdown < Grape::API
     params do
diff --git a/lib/api/members.rb b/lib/api/members.rb
index 4d8e23dee91..a8f67be3463 100644
--- a/lib/api/members.rb
+++ b/lib/api/members.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Members < Grape::API
     include PaginationParams
diff --git a/lib/api/merge_request_diffs.rb b/lib/api/merge_request_diffs.rb
index 95ef8f42954..e4fb890960a 100644
--- a/lib/api/merge_request_diffs.rb
+++ b/lib/api/merge_request_diffs.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # MergeRequestDiff API
   class MergeRequestDiffs < Grape::API
diff --git a/lib/api/merge_requests.rb b/lib/api/merge_requests.rb
index cad38271cbb..764905ca00f 100644
--- a/lib/api/merge_requests.rb
+++ b/lib/api/merge_requests.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class MergeRequests < Grape::API
     include PaginationParams
diff --git a/lib/api/milestone_responses.rb b/lib/api/milestone_responses.rb
index a8eb137e46a..a0ca39b69d4 100644
--- a/lib/api/milestone_responses.rb
+++ b/lib/api/milestone_responses.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module MilestoneResponses
     extend ActiveSupport::Concern
diff --git a/lib/api/namespaces.rb b/lib/api/namespaces.rb
index 32b77aedba8..76639fbb031 100644
--- a/lib/api/namespaces.rb
+++ b/lib/api/namespaces.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Namespaces < Grape::API
     include PaginationParams
diff --git a/lib/api/notes.rb b/lib/api/notes.rb
index dc9373bb3c2..9f323b87baf 100644
--- a/lib/api/notes.rb
+++ b/lib/api/notes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Notes < Grape::API
     include PaginationParams
diff --git a/lib/api/notification_settings.rb b/lib/api/notification_settings.rb
index bf0d6b9e434..4d9a4629268 100644
--- a/lib/api/notification_settings.rb
+++ b/lib/api/notification_settings.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # notification_settings API
   class NotificationSettings < Grape::API
diff --git a/lib/api/pages_domains.rb b/lib/api/pages_domains.rb
index 8730c91b426..c9ad47e0f0d 100644
--- a/lib/api/pages_domains.rb
+++ b/lib/api/pages_domains.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class PagesDomains < Grape::API
     include PaginationParams
diff --git a/lib/api/pagination_params.rb b/lib/api/pagination_params.rb
index f566eb3ed2b..ae03595eb25 100644
--- a/lib/api/pagination_params.rb
+++ b/lib/api/pagination_params.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Concern for declare pagination params.
   #
diff --git a/lib/api/pipeline_schedules.rb b/lib/api/pipeline_schedules.rb
index 5bd1ce8c5e1..ed0a38b9d70 100644
--- a/lib/api/pipeline_schedules.rb
+++ b/lib/api/pipeline_schedules.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class PipelineSchedules < Grape::API
     include PaginationParams
diff --git a/lib/api/pipelines.rb b/lib/api/pipelines.rb
index 5cce96d5ae7..1cfb982c04b 100644
--- a/lib/api/pipelines.rb
+++ b/lib/api/pipelines.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Pipelines < Grape::API
     include PaginationParams
diff --git a/lib/api/project_export.rb b/lib/api/project_export.rb
index 8562ae6d737..e34ed0bdb44 100644
--- a/lib/api/project_export.rb
+++ b/lib/api/project_export.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectExport < Grape::API
     before do
diff --git a/lib/api/project_hooks.rb b/lib/api/project_hooks.rb
index 0fb454bc22e..4af4c6ac593 100644
--- a/lib/api/project_hooks.rb
+++ b/lib/api/project_hooks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectHooks < Grape::API
     include PaginationParams
diff --git a/lib/api/project_import.rb b/lib/api/project_import.rb
index bc5152e539f..cbfa0c5bc1c 100644
--- a/lib/api/project_import.rb
+++ b/lib/api/project_import.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectImport < Grape::API
     include PaginationParams
diff --git a/lib/api/project_milestones.rb b/lib/api/project_milestones.rb
index 72cf32d7717..c7137ba5217 100644
--- a/lib/api/project_milestones.rb
+++ b/lib/api/project_milestones.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectMilestones < Grape::API
     include PaginationParams
diff --git a/lib/api/project_snapshots.rb b/lib/api/project_snapshots.rb
index 71005acc587..175fbb2ce92 100644
--- a/lib/api/project_snapshots.rb
+++ b/lib/api/project_snapshots.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectSnapshots < Grape::API
     helpers ::API::Helpers::ProjectSnapshotsHelpers
diff --git a/lib/api/project_snippets.rb b/lib/api/project_snippets.rb
index 1ef176b1320..f3a1b73b153 100644
--- a/lib/api/project_snippets.rb
+++ b/lib/api/project_snippets.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProjectSnippets < Grape::API
     include PaginationParams
diff --git a/lib/api/projects.rb b/lib/api/projects.rb
index ee426f39523..00bad49ebdc 100644
--- a/lib/api/projects.rb
+++ b/lib/api/projects.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency 'declarative_policy'
 
 module API
diff --git a/lib/api/projects_relation_builder.rb b/lib/api/projects_relation_builder.rb
index 9fd79c491c2..8edcfea7c93 100644
--- a/lib/api/projects_relation_builder.rb
+++ b/lib/api/projects_relation_builder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module ProjectsRelationBuilder
     extend ActiveSupport::Concern
diff --git a/lib/api/protected_branches.rb b/lib/api/protected_branches.rb
index 804f6fa9b73..47752f40e58 100644
--- a/lib/api/protected_branches.rb
+++ b/lib/api/protected_branches.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProtectedBranches < Grape::API
     include PaginationParams
diff --git a/lib/api/protected_tags.rb b/lib/api/protected_tags.rb
index e406344e42d..ed1c5f0cc05 100644
--- a/lib/api/protected_tags.rb
+++ b/lib/api/protected_tags.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class ProtectedTags < Grape::API
     include PaginationParams
diff --git a/lib/api/repositories.rb b/lib/api/repositories.rb
index 79736107bbb..5125f302fbb 100644
--- a/lib/api/repositories.rb
+++ b/lib/api/repositories.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mime/types'
 
 module API
diff --git a/lib/api/runner.rb b/lib/api/runner.rb
index b2d46cef23c..d8768a54986 100644
--- a/lib/api/runner.rb
+++ b/lib/api/runner.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Runner < Grape::API
     helpers ::API::Helpers::Runner
diff --git a/lib/api/runners.rb b/lib/api/runners.rb
index 9bcdfc8cb15..60868821810 100644
--- a/lib/api/runners.rb
+++ b/lib/api/runners.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Runners < Grape::API
     include PaginationParams
diff --git a/lib/api/scope.rb b/lib/api/scope.rb
index d5165b2e482..707775e5d15 100644
--- a/lib/api/scope.rb
+++ b/lib/api/scope.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Encapsulate a scope used for authorization, such as `api`, or `read_user`
 module API
   class Scope
diff --git a/lib/api/search.rb b/lib/api/search.rb
index 37fbabe419c..12d97dcfe7f 100644
--- a/lib/api/search.rb
+++ b/lib/api/search.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Search < Grape::API
     include PaginationParams
diff --git a/lib/api/settings.rb b/lib/api/settings.rb
index 8d71bd9dff1..edbd134822c 100644
--- a/lib/api/settings.rb
+++ b/lib/api/settings.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Settings < Grape::API
     before { authenticated_as_admin! }
diff --git a/lib/api/sidekiq_metrics.rb b/lib/api/sidekiq_metrics.rb
index 11f2b40269a..daa9598a204 100644
--- a/lib/api/sidekiq_metrics.rb
+++ b/lib/api/sidekiq_metrics.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'sidekiq/api'
 
 module API
diff --git a/lib/api/snippets.rb b/lib/api/snippets.rb
index 6352a9c8742..f1786c15f4f 100644
--- a/lib/api/snippets.rb
+++ b/lib/api/snippets.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   # Snippets API
   class Snippets < Grape::API
diff --git a/lib/api/subscriptions.rb b/lib/api/subscriptions.rb
index b3e1e23031a..077e9373ac4 100644
--- a/lib/api/subscriptions.rb
+++ b/lib/api/subscriptions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Subscriptions < Grape::API
     before { authenticate! }
diff --git a/lib/api/system_hooks.rb b/lib/api/system_hooks.rb
index 07552aa18e8..51fae0e54aa 100644
--- a/lib/api/system_hooks.rb
+++ b/lib/api/system_hooks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class SystemHooks < Grape::API
     include PaginationParams
diff --git a/lib/api/tags.rb b/lib/api/tags.rb
index 5e0afc6a7e4..f739eacf9ba 100644
--- a/lib/api/tags.rb
+++ b/lib/api/tags.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Tags < Grape::API
     include PaginationParams
diff --git a/lib/api/templates.rb b/lib/api/templates.rb
index 7bf0e0f5934..8ff3b2ac33c 100644
--- a/lib/api/templates.rb
+++ b/lib/api/templates.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Templates < Grape::API
     include PaginationParams
diff --git a/lib/api/time_tracking_endpoints.rb b/lib/api/time_tracking_endpoints.rb
index 2bb451dea89..93fe06bec27 100644
--- a/lib/api/time_tracking_endpoints.rb
+++ b/lib/api/time_tracking_endpoints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   module TimeTrackingEndpoints
     extend ActiveSupport::Concern
diff --git a/lib/api/todos.rb b/lib/api/todos.rb
index c6dbcf84e3a..ed2cf2cc31b 100644
--- a/lib/api/todos.rb
+++ b/lib/api/todos.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Todos < Grape::API
     include PaginationParams
diff --git a/lib/api/triggers.rb b/lib/api/triggers.rb
index 2339505b05b..f784c857883 100644
--- a/lib/api/triggers.rb
+++ b/lib/api/triggers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Triggers < Grape::API
     include PaginationParams
diff --git a/lib/api/users.rb b/lib/api/users.rb
index ac09ca7f7b7..ec7a7c6136d 100644
--- a/lib/api/users.rb
+++ b/lib/api/users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Users < Grape::API
     include PaginationParams
diff --git a/lib/api/variables.rb b/lib/api/variables.rb
index 50e6fa6bcdf..c844ba321ed 100644
--- a/lib/api/variables.rb
+++ b/lib/api/variables.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Variables < Grape::API
     include PaginationParams
diff --git a/lib/api/version.rb b/lib/api/version.rb
index 3b10bfa6a7d..74cd857f447 100644
--- a/lib/api/version.rb
+++ b/lib/api/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Version < Grape::API
     before { authenticate! }
diff --git a/lib/api/wikis.rb b/lib/api/wikis.rb
index e86ebc573f2..6e1d4eb335f 100644
--- a/lib/api/wikis.rb
+++ b/lib/api/wikis.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module API
   class Wikis < Grape::API
     helpers do