Optimize cache invalidation when running RuboCop as a gem [See ruboco…

…p#8633]

lib/rubocop.rb

@@ -1,8 +1,9 @@
 # frozen_string_literal: true
 
+require 'English'
+before_us = $LOADED_FEATURES.dup
 require 'rainbow'
 
-require 'English'
 require 'set'
 require 'forwardable'
 require 'regexp_parser'
@@ -627,3 +628,7 @@
 require_relative 'rubocop/remote_config'
 require_relative 'rubocop/target_ruby'
 require_relative 'rubocop/yaml_duplication_checker'
+
+unless File.exist?("#{__dir__}/../Gemfile") # Check if we are a gem
+  RuboCop::ResultCache.rubocop_required_features = $LOADED_FEATURES - before_us
+end

lib/rubocop/result_cache.rb

@@ -30,6 +30,11 @@ def self.cleanup(config_store, verbose, cache_root = nil)
     end
 
     class << self
+      # @api private
+      attr_accessor :rubocop_required_features
+
+      ResultCache.rubocop_required_features = []
+
       private
 
       def requires_file_removal?(file_count, config_store)
@@ -159,27 +164,31 @@ class << self
     end
 
     # The checksum of the rubocop program running the inspection.
-    # rubocop:disable Metrics/AbcSize
     def rubocop_checksum
       ResultCache.source_checksum ||=
         begin
-          lib_root = File.join(File.dirname(__FILE__), '..')
-          exe_root = File.join(lib_root, '..', 'exe')
-
-          # These are all the files we have `require`d plus everything in the
-          # exe directory. A change to any of them could affect the cop output
-          # so we include them in the cache hash.
-          source_files = $LOADED_FEATURES + Find.find(exe_root).to_a
-
           digest = Digest::SHA1.new
-          source_files
+          rubocop_extra_features
             .select { |path| File.file?(path) }
             .sort!
             .each { |path| digest << File.mtime(path).to_s }
+          digest << RuboCop::Version::STRING << RuboCop::AST::Version::STRING
           digest.hexdigest
         end
     end
-    # rubocop:enable Metrics/AbcSize
+
+    def rubocop_extra_features
+      lib_root = File.join(File.dirname(__FILE__), '..')
+      exe_root = File.join(lib_root, '..', 'exe')
+
+      # These are all the files we have `require`d plus everything in the
+      # exe directory. A change to any of them could affect the cop output
+      # so we include them in the cache hash.
+      source_files = $LOADED_FEATURES + Find.find(exe_root).to_a
+      source_files -= ResultCache.rubocop_required_features # Rely on gem versions
+
+      source_files
+    end
 
     # Return a hash of the options given at invocation, minus the ones that have
     # no effect on which offenses and disabled line ranges are found, and thus