Turn on performance based cops

Use attr_reader/attr_writer instead of methods

method is 12% slower

Use flat_map over map.flatten(1)

flatten is 66% slower

Use hash[]= instead of hash.merge! with single arguments

merge! is 166% slower

See https://github.com/rails/rails/pull/32337 for more conversation

5 files changed, 12 insertions, 22 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index a1b841ec3d..c266b432c0 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -497,9 +497,7 @@ module ActiveSupport
           arg.halted || !@user_conditions.all? { |c| c.call(arg.target, arg.value) }
         end
 
-        def nested
-          @nested
-        end
+        attr_reader :nested
 
         def final?
           !@call_template
@@ -578,7 +576,7 @@ module ActiveSupport
         end
 
         protected
-          def chain; @chain; end
+          attr_reader :chain
 
         private
 
diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 8b73270894..404404cad1 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -210,9 +210,7 @@ module ActiveSupport
         OpenSSL::Cipher.new(@cipher)
       end
 
-      def verifier
-        @verifier
-      end
+      attr_reader :verifier
 
       def aead_mode?
         @aead_mode ||= new_cipher.authenticated?
diff --git a/activesupport/lib/active_support/testing/parallelization.rb b/activesupport/lib/active_support/testing/parallelization.rb
index 59c8486f41..1caac1feb3 100644
--- a/activesupport/lib/active_support/testing/parallelization.rb
+++ b/activesupport/lib/active_support/testing/parallelization.rb
@@ -26,25 +26,21 @@ module ActiveSupport
         def pop; @queue.pop; end
       end
 
-      @after_fork_hooks = []
+      @@after_fork_hooks = []
 
       def self.after_fork_hook(&blk)
-        @after_fork_hooks << blk
+        @@after_fork_hooks << blk
       end
 
-      def self.after_fork_hooks
-        @after_fork_hooks
-      end
+      cattr_reader :after_fork_hooks
 
-      @run_cleanup_hooks = []
+      @@run_cleanup_hooks = []
 
       def self.run_cleanup_hook(&blk)
-        @run_cleanup_hooks << blk
+        @@run_cleanup_hooks << blk
       end
 
-      def self.run_cleanup_hooks
-        @run_cleanup_hooks
-      end
+      cattr_reader :run_cleanup_hooks
 
       def initialize(queue_size)
         @queue_size = queue_size
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index 792c88415c..fd07a3a6a2 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -265,7 +265,7 @@ module ActiveSupport
       private
         def load_country_zones(code)
           country = TZInfo::Country.get(code)
-          country.zone_identifiers.map do |tz_id|
+          country.zone_identifiers.flat_map do |tz_id|
             if MAPPING.value?(tz_id)
               MAPPING.inject([]) do |memo, (key, value)|
                 memo << self[key] if value == tz_id
@@ -274,7 +274,7 @@ module ActiveSupport
             else
               create(tz_id, nil, TZInfo::Timezone.new(tz_id))
             end
-          end.flatten(1).sort!
+          end.sort!
         end
 
         def zones_map
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
index 3b873de383..305a2c184d 100644
--- a/activesupport/test/cache/stores/redis_cache_store_test.rb
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -103,9 +103,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
 
     private
       def build(**kwargs)
-        ActiveSupport::Cache::RedisCacheStore.new(driver: DRIVER, **kwargs).tap do |cache|
-          cache.redis
-        end
+        ActiveSupport::Cache::RedisCacheStore.new(driver: DRIVER, **kwargs).tap(&:redis)
       end
   end