Enable even more frozen string for lib/gitlab

Enables frozen string for the following:

* lib/gitlab/patch/**/*.rb
* lib/gitlab/popen/**/*.rb
* lib/gitlab/profiler/**/*.rb
* lib/gitlab/project_authorizations/**/*.rb
* lib/gitlab/prometheus/**/*.rb
* lib/gitlab/query_limiting/**/*.rb
* lib/gitlab/quick_actions/**/*.rb
* lib/gitlab/redis/**/*.rb
* lib/gitlab/request_profiler/**/*.rb
* lib/gitlab/search/**/*.rb
* lib/gitlab/sherlock/**/*.rb
* lib/gitlab/sidekiq_middleware/**/*.rb
* lib/gitlab/slash_commands/**/*.rb
* lib/gitlab/sql/**/*.rb
* lib/gitlab/template/**/*.rb
* lib/gitlab/testing/**/*.rb
* lib/gitlab/utils/**/*.rb
* lib/gitlab/webpack/**/*.rb

Partially addresses gitlab-org/gitlab-ce#47424.

102 files changed, 217 insertions, 9 deletions

diff --git a/changelogs/unreleased/frozen-string-lib-gitlab-even-even-even-more.yml b/changelogs/unreleased/frozen-string-lib-gitlab-even-even-even-more.yml
new file mode 100644
index 00000000000..e718d716647
--- /dev/null
+++ b/changelogs/unreleased/frozen-string-lib-gitlab-even-even-even-more.yml
@@ -0,0 +1,5 @@
+---
+title: Enable even more frozen string for lib/gitlab
+merge_request:
+author: gfyoung
+type: performance
diff --git a/lib/gitlab/ci/config/entry/retry.rb b/lib/gitlab/ci/config/entry/retry.rb
index e39cc5de229..ee82ab10f9c 100644
--- a/lib/gitlab/ci/config/entry/retry.rb
+++ b/lib/gitlab/ci/config/entry/retry.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Ci
     class Config
diff --git a/lib/gitlab/performance_bar/peek_query_tracker.rb b/lib/gitlab/performance_bar/peek_query_tracker.rb
index 37ff32b1296..ac392432427 100644
--- a/lib/gitlab/performance_bar/peek_query_tracker.rb
+++ b/lib/gitlab/performance_bar/peek_query_tracker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Inspired by https://github.com/peek/peek-pg/blob/master/lib/peek/views/pg.rb
 # PEEK_DB_CLIENT is a constant set in config/initializers/peek.rb
 module Gitlab
diff --git a/lib/gitlab/popen/runner.rb b/lib/gitlab/popen/runner.rb
index f44035a48bb..cd9ad270cd8 100644
--- a/lib/gitlab/popen/runner.rb
+++ b/lib/gitlab/popen/runner.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Popen
     class Runner
diff --git a/lib/gitlab/profiler/total_time_flat_printer.rb b/lib/gitlab/profiler/total_time_flat_printer.rb
index 2fd0ec10ba8..2c105d2722b 100644
--- a/lib/gitlab/profiler/total_time_flat_printer.rb
+++ b/lib/gitlab/profiler/total_time_flat_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Profiler
     class TotalTimeFlatPrinter < RubyProf::FlatPrinter
diff --git a/lib/gitlab/project_authorizations/with_nested_groups.rb b/lib/gitlab/project_authorizations/with_nested_groups.rb
index 448c3f3a7d8..2372a316ab0 100644
--- a/lib/gitlab/project_authorizations/with_nested_groups.rb
+++ b/lib/gitlab/project_authorizations/with_nested_groups.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module ProjectAuthorizations
     # Calculating new project authorizations when supporting nested groups.
diff --git a/lib/gitlab/project_authorizations/without_nested_groups.rb b/lib/gitlab/project_authorizations/without_nested_groups.rb
index ed2287dcc7e..50b41b17649 100644
--- a/lib/gitlab/project_authorizations/without_nested_groups.rb
+++ b/lib/gitlab/project_authorizations/without_nested_groups.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module ProjectAuthorizations
     # Calculating new project authorizations when not supporting nested groups.
diff --git a/lib/gitlab/prometheus/additional_metrics_parser.rb b/lib/gitlab/prometheus/additional_metrics_parser.rb
index a240d090074..bd4ca578840 100644
--- a/lib/gitlab/prometheus/additional_metrics_parser.rb
+++ b/lib/gitlab/prometheus/additional_metrics_parser.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module AdditionalMetricsParser
diff --git a/lib/gitlab/prometheus/metric.rb b/lib/gitlab/prometheus/metric.rb
index 13cc59df795..7ebfc2e25a9 100644
--- a/lib/gitlab/prometheus/metric.rb
+++ b/lib/gitlab/prometheus/metric.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     class Metric
diff --git a/lib/gitlab/prometheus/metric_group.rb b/lib/gitlab/prometheus/metric_group.rb
index d696a8fc00c..8f30cdee232 100644
--- a/lib/gitlab/prometheus/metric_group.rb
+++ b/lib/gitlab/prometheus/metric_group.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     class MetricGroup
diff --git a/lib/gitlab/prometheus/parsing_error.rb b/lib/gitlab/prometheus/parsing_error.rb
index 49cc0e16080..20b5ef5ce55 100644
--- a/lib/gitlab/prometheus/parsing_error.rb
+++ b/lib/gitlab/prometheus/parsing_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     ParsingError = Class.new(StandardError)
diff --git a/lib/gitlab/prometheus/queries/additional_metrics_deployment_query.rb b/lib/gitlab/prometheus/queries/additional_metrics_deployment_query.rb
index fa86d2dfd6c..ab6ef7d5466 100644
--- a/lib/gitlab/prometheus/queries/additional_metrics_deployment_query.rb
+++ b/lib/gitlab/prometheus/queries/additional_metrics_deployment_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/additional_metrics_environment_query.rb b/lib/gitlab/prometheus/queries/additional_metrics_environment_query.rb
index 09f8f1103d2..34b705138ba 100644
--- a/lib/gitlab/prometheus/queries/additional_metrics_environment_query.rb
+++ b/lib/gitlab/prometheus/queries/additional_metrics_environment_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/base_query.rb b/lib/gitlab/prometheus/queries/base_query.rb
index 29cab6e9c15..9ff414d5236 100644
--- a/lib/gitlab/prometheus/queries/base_query.rb
+++ b/lib/gitlab/prometheus/queries/base_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/deployment_query.rb b/lib/gitlab/prometheus/queries/deployment_query.rb
index 3a609a795ba..fc32c4353f0 100644
--- a/lib/gitlab/prometheus/queries/deployment_query.rb
+++ b/lib/gitlab/prometheus/queries/deployment_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/environment_query.rb b/lib/gitlab/prometheus/queries/environment_query.rb
index 4d8b136d7af..56195f85a70 100644
--- a/lib/gitlab/prometheus/queries/environment_query.rb
+++ b/lib/gitlab/prometheus/queries/environment_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/matched_metric_query.rb b/lib/gitlab/prometheus/queries/matched_metric_query.rb
index d920e9a749f..32294756aa2 100644
--- a/lib/gitlab/prometheus/queries/matched_metric_query.rb
+++ b/lib/gitlab/prometheus/queries/matched_metric_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/prometheus/queries/query_additional_metrics.rb b/lib/gitlab/prometheus/queries/query_additional_metrics.rb
index 3be35f189d0..43508af96a7 100644
--- a/lib/gitlab/prometheus/queries/query_additional_metrics.rb
+++ b/lib/gitlab/prometheus/queries/query_additional_metrics.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Prometheus
     module Queries
diff --git a/lib/gitlab/query_limiting/active_support_subscriber.rb b/lib/gitlab/query_limiting/active_support_subscriber.rb
index 3c4ff5d1928..065862174bb 100644
--- a/lib/gitlab/query_limiting/active_support_subscriber.rb
+++ b/lib/gitlab/query_limiting/active_support_subscriber.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QueryLimiting
     class ActiveSupportSubscriber < ActiveSupport::Subscriber
diff --git a/lib/gitlab/query_limiting/transaction.rb b/lib/gitlab/query_limiting/transaction.rb
index 66d7d9275cf..e8fad067fa6 100644
--- a/lib/gitlab/query_limiting/transaction.rb
+++ b/lib/gitlab/query_limiting/transaction.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QueryLimiting
     class Transaction
@@ -68,7 +70,7 @@ module Gitlab
 
       def error_message
         header = 'Too many SQL queries were executed'
-        header += " in #{action}" if action
+        header = "#{header} in #{action}" if action
 
         "#{header}: a maximum of #{THRESHOLD} is allowed but #{count} SQL queries were executed"
       end
diff --git a/lib/gitlab/quick_actions/command_definition.rb b/lib/gitlab/quick_actions/command_definition.rb
index c682eb22890..259345b8a9a 100644
--- a/lib/gitlab/quick_actions/command_definition.rb
+++ b/lib/gitlab/quick_actions/command_definition.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QuickActions
     class CommandDefinition
diff --git a/lib/gitlab/quick_actions/dsl.rb b/lib/gitlab/quick_actions/dsl.rb
index 192c7ec2ff5..a3aab92061b 100644
--- a/lib/gitlab/quick_actions/dsl.rb
+++ b/lib/gitlab/quick_actions/dsl.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QuickActions
     module Dsl
diff --git a/lib/gitlab/quick_actions/extractor.rb b/lib/gitlab/quick_actions/extractor.rb
index 59f8dd889aa..ff9bb293b47 100644
--- a/lib/gitlab/quick_actions/extractor.rb
+++ b/lib/gitlab/quick_actions/extractor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QuickActions
     # This class takes an array of commands that should be extracted from a
diff --git a/lib/gitlab/quick_actions/spend_time_and_date_separator.rb b/lib/gitlab/quick_actions/spend_time_and_date_separator.rb
index 7328c517a30..f5176376a60 100644
--- a/lib/gitlab/quick_actions/spend_time_and_date_separator.rb
+++ b/lib/gitlab/quick_actions/spend_time_and_date_separator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QuickActions
     # This class takes spend command argument
diff --git a/lib/gitlab/quick_actions/substitution_definition.rb b/lib/gitlab/quick_actions/substitution_definition.rb
index 688056e5d73..2f78ea05cf0 100644
--- a/lib/gitlab/quick_actions/substitution_definition.rb
+++ b/lib/gitlab/quick_actions/substitution_definition.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module QuickActions
     class SubstitutionDefinition < CommandDefinition
diff --git a/lib/gitlab/redis/cache.rb b/lib/gitlab/redis/cache.rb
index a991933e910..6e8403ad878 100644
--- a/lib/gitlab/redis/cache.rb
+++ b/lib/gitlab/redis/cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # please require all dependencies below:
 require_relative 'wrapper' unless defined?(::Rails) && ::Rails.root.present?
 
diff --git a/lib/gitlab/redis/queues.rb b/lib/gitlab/redis/queues.rb
index e1695aafbeb..8b42c269dd0 100644
--- a/lib/gitlab/redis/queues.rb
+++ b/lib/gitlab/redis/queues.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # please require all dependencies below:
 require_relative 'wrapper' unless defined?(::Gitlab::Redis::Wrapper)
 
diff --git a/lib/gitlab/redis/shared_state.rb b/lib/gitlab/redis/shared_state.rb
index e5a0fdae7ef..9066606ca21 100644
--- a/lib/gitlab/redis/shared_state.rb
+++ b/lib/gitlab/redis/shared_state.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # please require all dependencies below:
 require_relative 'wrapper' unless defined?(::Gitlab::Redis::Wrapper)
 
diff --git a/lib/gitlab/redis/wrapper.rb b/lib/gitlab/redis/wrapper.rb
index 4178b436acf..07a1e20b076 100644
--- a/lib/gitlab/redis/wrapper.rb
+++ b/lib/gitlab/redis/wrapper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file should only be used by sub-classes, not directly by any clients of the sub-classes
 # please require all dependencies below:
 require 'active_support/core_ext/hash/keys'
diff --git a/lib/gitlab/request_profiler/middleware.rb b/lib/gitlab/request_profiler/middleware.rb
index ef42b0557e0..7615f6f443b 100644
--- a/lib/gitlab/request_profiler/middleware.rb
+++ b/lib/gitlab/request_profiler/middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'ruby-prof'
 
 module Gitlab
diff --git a/lib/gitlab/request_profiler/profile.rb b/lib/gitlab/request_profiler/profile.rb
index f89d56903ef..46996ef8c51 100644
--- a/lib/gitlab/request_profiler/profile.rb
+++ b/lib/gitlab/request_profiler/profile.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module RequestProfiler
     class Profile
diff --git a/lib/gitlab/sanitizers/svg.rb b/lib/gitlab/sanitizers/svg.rb
index 8304b9a482c..0d4e6be2129 100644
--- a/lib/gitlab/sanitizers/svg.rb
+++ b/lib/gitlab/sanitizers/svg.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sanitizers
     module SVG
diff --git a/lib/gitlab/sanitizers/svg/whitelist.rb b/lib/gitlab/sanitizers/svg/whitelist.rb
index d50f826f924..b4da24b3215 100644
--- a/lib/gitlab/sanitizers/svg/whitelist.rb
+++ b/lib/gitlab/sanitizers/svg/whitelist.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Generated from:
 # SVG element list: https://www.w3.org/TR/SVG/eltindex.html
 # SVG Attribute list: https://www.w3.org/TR/SVG/attindex.html
diff --git a/lib/gitlab/search/parsed_query.rb b/lib/gitlab/search/parsed_query.rb
index 23595f23f01..c4fb0199558 100644
--- a/lib/gitlab/search/parsed_query.rb
+++ b/lib/gitlab/search/parsed_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Search
     class ParsedQuery
diff --git a/lib/gitlab/search/query.rb b/lib/gitlab/search/query.rb
index 8583bce7792..7f69083a492 100644
--- a/lib/gitlab/search/query.rb
+++ b/lib/gitlab/search/query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Search
     class Query < SimpleDelegator
diff --git a/lib/gitlab/serializer/ci/variables.rb b/lib/gitlab/serializer/ci/variables.rb
index 292c8de6229..9abf3a54f37 100644
--- a/lib/gitlab/serializer/ci/variables.rb
+++ b/lib/gitlab/serializer/ci/variables.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Serializer
     module Ci
diff --git a/lib/gitlab/serializer/pagination.rb b/lib/gitlab/serializer/pagination.rb
index 6bb00d8ae21..eb242cc7c20 100644
--- a/lib/gitlab/serializer/pagination.rb
+++ b/lib/gitlab/serializer/pagination.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Serializer
     class Pagination
diff --git a/lib/gitlab/sherlock/collection.rb b/lib/gitlab/sherlock/collection.rb
index 66bd6258521..ce3a376cf75 100644
--- a/lib/gitlab/sherlock/collection.rb
+++ b/lib/gitlab/sherlock/collection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     # A collection of transactions recorded by Sherlock.
diff --git a/lib/gitlab/sherlock/file_sample.rb b/lib/gitlab/sherlock/file_sample.rb
index 89072b01f2e..604b6df12cc 100644
--- a/lib/gitlab/sherlock/file_sample.rb
+++ b/lib/gitlab/sherlock/file_sample.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     class FileSample
diff --git a/lib/gitlab/sherlock/line_profiler.rb b/lib/gitlab/sherlock/line_profiler.rb
index b5f9d040047..209ba784f9c 100644
--- a/lib/gitlab/sherlock/line_profiler.rb
+++ b/lib/gitlab/sherlock/line_profiler.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     # Class for profiling code on a per line basis.
diff --git a/lib/gitlab/sherlock/line_sample.rb b/lib/gitlab/sherlock/line_sample.rb
index eb1948eb6d6..c92fa9ea1ff 100644
--- a/lib/gitlab/sherlock/line_sample.rb
+++ b/lib/gitlab/sherlock/line_sample.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     class LineSample
diff --git a/lib/gitlab/sherlock/location.rb b/lib/gitlab/sherlock/location.rb
index 5ac265618ad..4bba60f3490 100644
--- a/lib/gitlab/sherlock/location.rb
+++ b/lib/gitlab/sherlock/location.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     class Location
diff --git a/lib/gitlab/sherlock/middleware.rb b/lib/gitlab/sherlock/middleware.rb
index 4c88e33699a..747cb0f9142 100644
--- a/lib/gitlab/sherlock/middleware.rb
+++ b/lib/gitlab/sherlock/middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     # Rack middleware used for tracking request metrics.
diff --git a/lib/gitlab/sherlock/query.rb b/lib/gitlab/sherlock/query.rb
index 02ddc3f47eb..11561eec32a 100644
--- a/lib/gitlab/sherlock/query.rb
+++ b/lib/gitlab/sherlock/query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     class Query
@@ -48,7 +50,7 @@ module Gitlab
         end
 
         unless @query.end_with?(';')
-          @query += ';'
+          @query = "#{@query};"
         end
       end
 
diff --git a/lib/gitlab/sherlock/transaction.rb b/lib/gitlab/sherlock/transaction.rb
index 400a552bf99..d04624977dc 100644
--- a/lib/gitlab/sherlock/transaction.rb
+++ b/lib/gitlab/sherlock/transaction.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Sherlock
     class Transaction
diff --git a/lib/gitlab/sidekiq_logging/json_formatter.rb b/lib/gitlab/sidekiq_logging/json_formatter.rb
index 98f8222fd03..88888c5994e 100644
--- a/lib/gitlab/sidekiq_logging/json_formatter.rb
+++ b/lib/gitlab/sidekiq_logging/json_formatter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqLogging
     class JSONFormatter
diff --git a/lib/gitlab/sidekiq_logging/structured_logger.rb b/lib/gitlab/sidekiq_logging/structured_logger.rb
index 9a89ae70b98..e86db8db3a1 100644
--- a/lib/gitlab/sidekiq_logging/structured_logger.rb
+++ b/lib/gitlab/sidekiq_logging/structured_logger.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqLogging
     class StructuredLogger
diff --git a/lib/gitlab/sidekiq_middleware/arguments_logger.rb b/lib/gitlab/sidekiq_middleware/arguments_logger.rb
index 82a59a7a87e..2859aa5f4a6 100644
--- a/lib/gitlab/sidekiq_middleware/arguments_logger.rb
+++ b/lib/gitlab/sidekiq_middleware/arguments_logger.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqMiddleware
     class ArgumentsLogger
diff --git a/lib/gitlab/sidekiq_middleware/request_store_middleware.rb b/lib/gitlab/sidekiq_middleware/request_store_middleware.rb
index b1fa0e3cb4e..8824f81e8e3 100644
--- a/lib/gitlab/sidekiq_middleware/request_store_middleware.rb
+++ b/lib/gitlab/sidekiq_middleware/request_store_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqMiddleware
     class RequestStoreMiddleware
diff --git a/lib/gitlab/sidekiq_middleware/shutdown.rb b/lib/gitlab/sidekiq_middleware/shutdown.rb
index b232ac4da33..19f3be83bce 100644
--- a/lib/gitlab/sidekiq_middleware/shutdown.rb
+++ b/lib/gitlab/sidekiq_middleware/shutdown.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mutex_m'
 
 module Gitlab
diff --git a/lib/gitlab/sidekiq_status/client_middleware.rb b/lib/gitlab/sidekiq_status/client_middleware.rb
index 00983b3284a..bfd5038557d 100644
--- a/lib/gitlab/sidekiq_status/client_middleware.rb
+++ b/lib/gitlab/sidekiq_status/client_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqStatus
     class ClientMiddleware
diff --git a/lib/gitlab/sidekiq_status/server_middleware.rb b/lib/gitlab/sidekiq_status/server_middleware.rb
index ceab10b8301..01bc58fd2be 100644
--- a/lib/gitlab/sidekiq_status/server_middleware.rb
+++ b/lib/gitlab/sidekiq_status/server_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqStatus
     class ServerMiddleware
diff --git a/lib/gitlab/sidekiq_versioning/manager.rb b/lib/gitlab/sidekiq_versioning/manager.rb
index 308be0fdf76..e5852b43003 100644
--- a/lib/gitlab/sidekiq_versioning/manager.rb
+++ b/lib/gitlab/sidekiq_versioning/manager.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SidekiqVersioning
     module Manager
diff --git a/lib/gitlab/slash_commands/base_command.rb b/lib/gitlab/slash_commands/base_command.rb
index 0c76378d51c..fcc120112f2 100644
--- a/lib/gitlab/slash_commands/base_command.rb
+++ b/lib/gitlab/slash_commands/base_command.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class BaseCommand
diff --git a/lib/gitlab/slash_commands/command.rb b/lib/gitlab/slash_commands/command.rb
index c82320a6036..474c09b9c4d 100644
--- a/lib/gitlab/slash_commands/command.rb
+++ b/lib/gitlab/slash_commands/command.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class Command < BaseCommand
diff --git a/lib/gitlab/slash_commands/deploy.rb b/lib/gitlab/slash_commands/deploy.rb
index b308fd9637f..157d924f99f 100644
--- a/lib/gitlab/slash_commands/deploy.rb
+++ b/lib/gitlab/slash_commands/deploy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class Deploy < BaseCommand
diff --git a/lib/gitlab/slash_commands/help.rb b/lib/gitlab/slash_commands/help.rb
index 81f3707e03e..dbe15baa3d7 100644
--- a/lib/gitlab/slash_commands/help.rb
+++ b/lib/gitlab/slash_commands/help.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class Help < BaseCommand
diff --git a/lib/gitlab/slash_commands/issue_command.rb b/lib/gitlab/slash_commands/issue_command.rb
index 3d96982b820..4c8dc4b1784 100644
--- a/lib/gitlab/slash_commands/issue_command.rb
+++ b/lib/gitlab/slash_commands/issue_command.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class IssueCommand < BaseCommand
diff --git a/lib/gitlab/slash_commands/issue_move.rb b/lib/gitlab/slash_commands/issue_move.rb
index 3985e635983..d2f1f130b38 100644
--- a/lib/gitlab/slash_commands/issue_move.rb
+++ b/lib/gitlab/slash_commands/issue_move.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class IssueMove < IssueCommand
diff --git a/lib/gitlab/slash_commands/issue_new.rb b/lib/gitlab/slash_commands/issue_new.rb
index 6396b828dc7..48379031537 100644
--- a/lib/gitlab/slash_commands/issue_new.rb
+++ b/lib/gitlab/slash_commands/issue_new.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class IssueNew < IssueCommand
diff --git a/lib/gitlab/slash_commands/issue_search.rb b/lib/gitlab/slash_commands/issue_search.rb
index ee78f0f832e..0a705de4484 100644
--- a/lib/gitlab/slash_commands/issue_search.rb
+++ b/lib/gitlab/slash_commands/issue_search.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class IssueSearch < IssueCommand
diff --git a/lib/gitlab/slash_commands/issue_show.rb b/lib/gitlab/slash_commands/issue_show.rb
index ffa5184e5cb..5f5fa32ff20 100644
--- a/lib/gitlab/slash_commands/issue_show.rb
+++ b/lib/gitlab/slash_commands/issue_show.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     class IssueShow < IssueCommand
diff --git a/lib/gitlab/slash_commands/presenters/access.rb b/lib/gitlab/slash_commands/presenters/access.rb
index 81f7cd3ffe8..fa163cb098e 100644
--- a/lib/gitlab/slash_commands/presenters/access.rb
+++ b/lib/gitlab/slash_commands/presenters/access.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/base.rb b/lib/gitlab/slash_commands/presenters/base.rb
index e13808a2720..73814aa180f 100644
--- a/lib/gitlab/slash_commands/presenters/base.rb
+++ b/lib/gitlab/slash_commands/presenters/base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/deploy.rb b/lib/gitlab/slash_commands/presenters/deploy.rb
index ebae0f57f9b..7d852eb1f9a 100644
--- a/lib/gitlab/slash_commands/presenters/deploy.rb
+++ b/lib/gitlab/slash_commands/presenters/deploy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/help.rb b/lib/gitlab/slash_commands/presenters/help.rb
index ab855319077..480d7aa6a30 100644
--- a/lib/gitlab/slash_commands/presenters/help.rb
+++ b/lib/gitlab/slash_commands/presenters/help.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/issue_base.rb b/lib/gitlab/slash_commands/presenters/issue_base.rb
index 31c1e97efba..b6db103b82b 100644
--- a/lib/gitlab/slash_commands/presenters/issue_base.rb
+++ b/lib/gitlab/slash_commands/presenters/issue_base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/issue_move.rb b/lib/gitlab/slash_commands/presenters/issue_move.rb
index 03921729941..ca0644ede95 100644
--- a/lib/gitlab/slash_commands/presenters/issue_move.rb
+++ b/lib/gitlab/slash_commands/presenters/issue_move.rb
@@ -1,4 +1,6 @@
 # coding: utf-8
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/issue_new.rb b/lib/gitlab/slash_commands/presenters/issue_new.rb
index 5964bfe9960..ac78745ae70 100644
--- a/lib/gitlab/slash_commands/presenters/issue_new.rb
+++ b/lib/gitlab/slash_commands/presenters/issue_new.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/issue_search.rb b/lib/gitlab/slash_commands/presenters/issue_search.rb
index 4e27d668685..0d497efec0e 100644
--- a/lib/gitlab/slash_commands/presenters/issue_search.rb
+++ b/lib/gitlab/slash_commands/presenters/issue_search.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
diff --git a/lib/gitlab/slash_commands/presenters/issue_show.rb b/lib/gitlab/slash_commands/presenters/issue_show.rb
index 562f15f403c..5a2c79a928e 100644
--- a/lib/gitlab/slash_commands/presenters/issue_show.rb
+++ b/lib/gitlab/slash_commands/presenters/issue_show.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SlashCommands
     module Presenters
@@ -38,10 +40,10 @@ module Gitlab
         end
 
         def text
-          message = "**#{status_text(@resource)}**"
+          message = ["**#{status_text(@resource)}**"]
 
           if @resource.upvotes.zero? && @resource.downvotes.zero? && @resource.user_notes_count.zero?
-            return message
+            return message.join
           end
 
           message << " · "
@@ -49,7 +51,7 @@ module Gitlab
           message << ":-1: #{@resource.downvotes} " unless @resource.downvotes.zero?
           message << ":speech_balloon: #{@resource.user_notes_count}" unless @resource.user_notes_count.zero?
 
-          message
+          message.join
         end
 
         def pretext
diff --git a/lib/gitlab/slash_commands/result.rb b/lib/gitlab/slash_commands/result.rb
index 3669dedf0fe..607c9c8dec1 100644
--- a/lib/gitlab/slash_commands/result.rb
+++ b/lib/gitlab/slash_commands/result.rb
@@ -1,4 +1,7 @@
-module Gitlab # rubocop:disable Naming/FileName
+# rubocop:disable Naming/FileName
+# frozen_string_literal: true
+
+module Gitlab
   module SlashCommands
     Result = Struct.new(:type, :message)
   end
diff --git a/lib/gitlab/sql/cte.rb b/lib/gitlab/sql/cte.rb
index f357829ba3f..7817a2a1ce2 100644
--- a/lib/gitlab/sql/cte.rb
+++ b/lib/gitlab/sql/cte.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SQL
     # Class for easily building CTE statements.
diff --git a/lib/gitlab/sql/glob.rb b/lib/gitlab/sql/glob.rb
index 5e89e12b2b1..f3421bd95d2 100644
--- a/lib/gitlab/sql/glob.rb
+++ b/lib/gitlab/sql/glob.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SQL
     module Glob
diff --git a/lib/gitlab/sql/pattern.rb b/lib/gitlab/sql/pattern.rb
index 53744bad1f4..92388262035 100644
--- a/lib/gitlab/sql/pattern.rb
+++ b/lib/gitlab/sql/pattern.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SQL
     module Pattern
diff --git a/lib/gitlab/sql/recursive_cte.rb b/lib/gitlab/sql/recursive_cte.rb
index 16ec002f139..ec1f00a3a91 100644
--- a/lib/gitlab/sql/recursive_cte.rb
+++ b/lib/gitlab/sql/recursive_cte.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SQL
     # Class for easily building recursive CTE statements.
diff --git a/lib/gitlab/sql/union.rb b/lib/gitlab/sql/union.rb
index c99b262f1ca..d24d5116167 100644
--- a/lib/gitlab/sql/union.rb
+++ b/lib/gitlab/sql/union.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module SQL
     # Class for building SQL UNION statements.
diff --git a/lib/gitlab/template/base_template.rb b/lib/gitlab/template/base_template.rb
index 699d747892c..0b4cc571dc0 100644
--- a/lib/gitlab/template/base_template.rb
+++ b/lib/gitlab/template/base_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class BaseTemplate
diff --git a/lib/gitlab/template/dockerfile_template.rb b/lib/gitlab/template/dockerfile_template.rb
index 20b054b0bd8..3b516bb862a 100644
--- a/lib/gitlab/template/dockerfile_template.rb
+++ b/lib/gitlab/template/dockerfile_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class DockerfileTemplate < BaseTemplate
diff --git a/lib/gitlab/template/finders/base_template_finder.rb b/lib/gitlab/template/finders/base_template_finder.rb
index a5105439b12..93c229af143 100644
--- a/lib/gitlab/template/finders/base_template_finder.rb
+++ b/lib/gitlab/template/finders/base_template_finder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     module Finders
diff --git a/lib/gitlab/template/finders/global_template_finder.rb b/lib/gitlab/template/finders/global_template_finder.rb
index b08d9a99e99..76bb9eb611e 100644
--- a/lib/gitlab/template/finders/global_template_finder.rb
+++ b/lib/gitlab/template/finders/global_template_finder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Searches and reads file present on GitLab installation directory
 module Gitlab
   module Template
@@ -21,7 +23,7 @@ module Gitlab
         end
 
         def list_files_for(dir)
-          dir << '/' unless dir.end_with?('/')
+          dir = "#{dir}/" unless dir.end_with?('/')
           Dir.glob(File.join(dir, "*#{@extension}")).select { |f| f =~ self.class.filter_regex(@extension) }
         end
 
diff --git a/lib/gitlab/template/finders/repo_template_finder.rb b/lib/gitlab/template/finders/repo_template_finder.rb
index 9140ace879f..b92cefefb8f 100644
--- a/lib/gitlab/template/finders/repo_template_finder.rb
+++ b/lib/gitlab/template/finders/repo_template_finder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Searches and reads files present on each GitLab project repository
 module Gitlab
   module Template
@@ -33,7 +35,7 @@ module Gitlab
         def list_files_for(dir)
           return [] unless @commit
 
-          dir << '/' unless dir.end_with?('/')
+          dir = "#{dir}/" unless dir.end_with?('/')
 
           entries = @repository.tree(:head, dir).entries
 
diff --git a/lib/gitlab/template/gitignore_template.rb b/lib/gitlab/template/gitignore_template.rb
index 8d2a9d2305c..72a1b7460c2 100644
--- a/lib/gitlab/template/gitignore_template.rb
+++ b/lib/gitlab/template/gitignore_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class GitignoreTemplate < BaseTemplate
diff --git a/lib/gitlab/template/gitlab_ci_yml_template.rb b/lib/gitlab/template/gitlab_ci_yml_template.rb
index deae53cc61b..fbefb5f7f0e 100644
--- a/lib/gitlab/template/gitlab_ci_yml_template.rb
+++ b/lib/gitlab/template/gitlab_ci_yml_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class GitlabCiYmlTemplate < BaseTemplate
diff --git a/lib/gitlab/template/issue_template.rb b/lib/gitlab/template/issue_template.rb
index c6fa8d3eafc..01b191733d4 100644
--- a/lib/gitlab/template/issue_template.rb
+++ b/lib/gitlab/template/issue_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class IssueTemplate < BaseTemplate
diff --git a/lib/gitlab/template/merge_request_template.rb b/lib/gitlab/template/merge_request_template.rb
index f826c02f3b5..357b31cd82e 100644
--- a/lib/gitlab/template/merge_request_template.rb
+++ b/lib/gitlab/template/merge_request_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Template
     class MergeRequestTemplate < BaseTemplate
diff --git a/lib/gitlab/testing/request_blocker_middleware.rb b/lib/gitlab/testing/request_blocker_middleware.rb
index 53333b9b06b..513cbe839ba 100644
--- a/lib/gitlab/testing/request_blocker_middleware.rb
+++ b/lib/gitlab/testing/request_blocker_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # rubocop:disable Style/ClassVars
 
 # This is inspired by http://www.salsify.com/blog/engineering/tearing-capybara-ajax-tests
diff --git a/lib/gitlab/testing/request_inspector_middleware.rb b/lib/gitlab/testing/request_inspector_middleware.rb
index c251e78f5c5..36cdfebcc28 100644
--- a/lib/gitlab/testing/request_inspector_middleware.rb
+++ b/lib/gitlab/testing/request_inspector_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # rubocop:disable Style/ClassVars
 
 module Gitlab
@@ -35,7 +37,7 @@ module Gitlab
         request_headers = env_http_headers(env)
         status, headers, body = @app.call(env)
 
-        full_body = ''
+        full_body = +''
         body.each { |b| full_body << b }
 
         request = OpenStruct.new(
diff --git a/lib/gitlab/utils/merge_hash.rb b/lib/gitlab/utils/merge_hash.rb
index 385141d44d0..fc237861e2f 100644
--- a/lib/gitlab/utils/merge_hash.rb
+++ b/lib/gitlab/utils/merge_hash.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Utils
     module MergeHash
diff --git a/lib/gitlab/utils/override.rb b/lib/gitlab/utils/override.rb
index d00921e6cdc..c412961ea3f 100644
--- a/lib/gitlab/utils/override.rb
+++ b/lib/gitlab/utils/override.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Utils
     module Override
diff --git a/lib/gitlab/utils/strong_memoize.rb b/lib/gitlab/utils/strong_memoize.rb
index fe091f4611b..aa1f8e2fdda 100644
--- a/lib/gitlab/utils/strong_memoize.rb
+++ b/lib/gitlab/utils/strong_memoize.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Utils
     module StrongMemoize
diff --git a/lib/gitlab/verify/batch_verifier.rb b/lib/gitlab/verify/batch_verifier.rb
index 167ba1b3149..dbda19a4a66 100644
--- a/lib/gitlab/verify/batch_verifier.rb
+++ b/lib/gitlab/verify/batch_verifier.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Verify
     class BatchVerifier
diff --git a/lib/gitlab/verify/job_artifacts.rb b/lib/gitlab/verify/job_artifacts.rb
index dbadfbde9e3..3b90c8b1a8e 100644
--- a/lib/gitlab/verify/job_artifacts.rb
+++ b/lib/gitlab/verify/job_artifacts.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Verify
     class JobArtifacts < BatchVerifier
diff --git a/lib/gitlab/verify/lfs_objects.rb b/lib/gitlab/verify/lfs_objects.rb
index d3f58a73ac7..20dbb7addff 100644
--- a/lib/gitlab/verify/lfs_objects.rb
+++ b/lib/gitlab/verify/lfs_objects.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Verify
     class LfsObjects < BatchVerifier
diff --git a/lib/gitlab/verify/rake_task.rb b/lib/gitlab/verify/rake_task.rb
index e190eaddc79..3efed311237 100644
--- a/lib/gitlab/verify/rake_task.rb
+++ b/lib/gitlab/verify/rake_task.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Verify
     class RakeTask
diff --git a/lib/gitlab/verify/uploads.rb b/lib/gitlab/verify/uploads.rb
index 201fcc7de7f..875e8a120e9 100644
--- a/lib/gitlab/verify/uploads.rb
+++ b/lib/gitlab/verify/uploads.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Verify
     class Uploads < BatchVerifier
diff --git a/lib/gitlab/view/presenter/base.rb b/lib/gitlab/view/presenter/base.rb
index c3fd6d317aa..5e70afe730a 100644
--- a/lib/gitlab/view/presenter/base.rb
+++ b/lib/gitlab/view/presenter/base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module View
     module Presenter
diff --git a/lib/gitlab/view/presenter/delegated.rb b/lib/gitlab/view/presenter/delegated.rb
index 387ff0f5d43..4a90ab758fb 100644
--- a/lib/gitlab/view/presenter/delegated.rb
+++ b/lib/gitlab/view/presenter/delegated.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module View
     module Presenter
diff --git a/lib/gitlab/view/presenter/factory.rb b/lib/gitlab/view/presenter/factory.rb
index 570f0723e39..302697ff8eb 100644
--- a/lib/gitlab/view/presenter/factory.rb
+++ b/lib/gitlab/view/presenter/factory.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module View
     module Presenter
diff --git a/lib/gitlab/view/presenter/simple.rb b/lib/gitlab/view/presenter/simple.rb
index b7653a0f3cc..31dcd1d4c4c 100644
--- a/lib/gitlab/view/presenter/simple.rb
+++ b/lib/gitlab/view/presenter/simple.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module View
     module Presenter
diff --git a/lib/gitlab/webpack/dev_server_middleware.rb b/lib/gitlab/webpack/dev_server_middleware.rb
index 529f7d6a8d6..fda41da5a94 100644
--- a/lib/gitlab/webpack/dev_server_middleware.rb
+++ b/lib/gitlab/webpack/dev_server_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This Rack middleware is intended to proxy the webpack assets directory to the
 # webpack-dev-server.  It is only intended for use in development.
 
diff --git a/lib/gitlab/webpack/manifest.rb b/lib/gitlab/webpack/manifest.rb
index 0c343e5bc1d..1d2aff5e5b4 100644
--- a/lib/gitlab/webpack/manifest.rb
+++ b/lib/gitlab/webpack/manifest.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'webpack/rails/manifest'
 
 module Gitlab