Optimize Commissioner callbacks

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 * [#8892](https://github.com/rubocop-hq/rubocop/issues/8892): Fix an error for `Style/StringConcatenation` when correcting nested concatenable parts. ([@fatkodima][])
 
+### Changes
+
+* [#8882](https://github.com/rubocop-hq/rubocop/pull/8882): **(Potentially breaking)** RuboCop assumes that Cop classes do not define new `on_<type>` methods at runtime (e.g. via `extend` in `initialize`). ([@marcandre][])
+
 ## 0.93.1 (2020-10-12)
 
 ### Bug fixes

lib/rubocop.rb

@@ -471,8 +471,6 @@
 require_relative 'rubocop/cop/style/redundant_file_extension_in_require'
 require_relative 'rubocop/cop/style/redundant_self_assignment'
 require_relative 'rubocop/cop/style/sole_nested_conditional'
-require_relative 'rubocop/cop/style/method_call_with_args_parentheses/omit_parentheses'
-require_relative 'rubocop/cop/style/method_call_with_args_parentheses/require_parentheses'
 require_relative 'rubocop/cop/style/method_called_on_do_end_block'
 require_relative 'rubocop/cop/style/method_def_parentheses'
 require_relative 'rubocop/cop/style/min_max'

lib/rubocop/cop/base.rb

@@ -261,6 +261,21 @@ def offenses
           'they are returned as the result of the investigation'
       end
 
+      ### Reserved for Commissioner
+
+      # @api private
+      def callbacks_needed
+        self.class.callbacks_needed
+      end
+
+      # @api private
+      def self.callbacks_needed
+        @callbacks_needed ||= public_instance_methods.select do |m|
+          m.match?(/^on_/) &&
+            !Base.method_defined?(m) # exclude standard "callbacks" like 'on_begin_investigation'
+        end
+      end
+
       private
 
       ### Reserved for Cop::Cop
@@ -291,7 +306,7 @@ def currently_disabled_lines
       end
 
       private_class_method def self.restrict_on_send
-        @restrict_on_send ||= self::RESTRICT_ON_SEND.to_set.freeze
+        @restrict_on_send ||= self::RESTRICT_ON_SEND.to_a.freeze
       end
 
       # Called before any investigation

lib/rubocop/cop/commissioner.rb

@@ -45,8 +45,7 @@ def initialize(cops, forces = [], options = {})
         @cops = cops
         @forces = forces
         @options = options
-        @callbacks = Hash.new { |h, k| h[k] = cops_callbacks_for(k) }
-        @restricted_map = {}
+        initialize_callbacks
 
         reset
       end
@@ -94,7 +93,7 @@ def investigate(processed_source)
       private
 
       def trigger_responding_cops(callback, node)
-        @callbacks[callback].each do |cop|
+        @callbacks[callback]&.each do |cop|
           with_cop_error_handling(cop, node) do
             cop.send(callback, node)
           end
@@ -105,19 +104,32 @@ def reset
         @errors = []
       end
 
-      def cops_callbacks_for(callback)
-        callbacks = @cops.select do |cop|
-          cop.respond_to?(callback)
-        end
-        if RESTRICTED_CALLBACKS.include?(callback)
-          @restricted_map[callback] = restricted_map(callbacks)
+      def initialize_callbacks
+        @callbacks = build_callbacks(@cops)
+        @restricted_map = restrict_callbacks(@callbacks)
+      end
+
+      def build_callbacks(cops)
+        callbacks = {}
+        cops.each do |cop|
+          cop.callbacks_needed.each do |callback|
+            (callbacks[callback] ||= []) << cop
+          end
         end
         callbacks
       end
 
+      def restrict_callbacks(callbacks)
+        restricted = {}
+        RESTRICTED_CALLBACKS.each do |callback|
+          restricted[callback] = restricted_map(callbacks[callback])
+        end
+        restricted
+      end
+
       def trigger_restricted_cops(event, node)
         name = node.method_name
-        @restricted_map.fetch(event)[name]&.each do |cop|
+        @restricted_map[event][name]&.each do |cop|
           with_cop_error_handling(cop, node) do
             cop.send(event, node)
           end
@@ -127,7 +139,7 @@ def trigger_restricted_cops(event, node)
       # Note: mutates `callbacks` in place
       def restricted_map(callbacks)
         map = {}
-        callbacks.select! do |cop|
+        callbacks&.select! do |cop|
           restrictions = cop.class.send :restrict_on_send
           restrictions.each do |name|
             (map[name] ||= []) << cop

lib/rubocop/cop/style/method_call_with_args_parentheses.rb

@@ -144,25 +144,22 @@ module Style
       #   # good
       #   Array 1
       class MethodCallWithArgsParentheses < Base
+        require_relative 'method_call_with_args_parentheses/omit_parentheses'
+        require_relative 'method_call_with_args_parentheses/require_parentheses'
+
         include ConfigurableEnforcedStyle
         include IgnoredMethods
         include IgnoredPattern
+        include RequireParentheses
+        include OmitParentheses
         extend AutoCorrector
 
-        def initialize(*)
-          super
-          return unless style_configured?
-
-          case style
-          when :require_parentheses
-            extend RequireParentheses
-          when :omit_parentheses
-            extend OmitParentheses
-          end
+        def on_send(node)
+          send(style, node) # call require_parentheses or omit_parentheses
         end
-
-        # @abstract Overridden in style modules
-        def autocorrect(_node); end
+        alias on_csend on_send
+        alias on_super on_send
+        alias on_yield on_send
 
         private
 

lib/rubocop/cop/style/method_call_with_args_parentheses/omit_parentheses.rb

@@ -7,15 +7,19 @@ class MethodCallWithArgsParentheses
         # Style omit_parentheses
         module OmitParentheses
           TRAILING_WHITESPACE_REGEX = /\s+\Z/.freeze
+          OMIT_MSG = 'Omit parentheses for method calls with arguments.'
+          private_constant :OMIT_MSG
 
-          def on_send(node)
+          private
+
+          def omit_parentheses(node)
             return unless node.parenthesized?
             return if node.implicit_call?
             return if super_call_without_arguments?(node)
             return if allowed_camel_case_method_call?(node)
             return if legitimate_call_with_parentheses?(node)
 
-            add_offense(offense_range(node)) do |corrector|
+            add_offense(offense_range(node), message: OMIT_MSG) do |corrector|
               if parentheses_at_the_end_of_multiline_call?(node)
                 corrector.replace(args_begin(node), ' \\')
               else
@@ -24,20 +28,11 @@ def on_send(node)
               corrector.remove(node.loc.end)
             end
           end
-          alias on_csend on_send
-          alias on_super on_send
-          alias on_yield on_send
-
-          private
 
           def offense_range(node)
             node.loc.begin.join(node.loc.end)
           end
 
-          def message(_range = nil)
-            'Omit parentheses for method calls with arguments.'
-          end
-
           def super_call_without_arguments?(node)
             node.super_type? && node.arguments.none?
           end

lib/rubocop/cop/style/method_call_with_args_parentheses/require_parentheses.rb

@@ -6,27 +6,23 @@ module Style
       class MethodCallWithArgsParentheses
         # Style require_parentheses
         module RequireParentheses
-          def on_send(node)
+          REQUIRE_MSG = 'Use parentheses for method calls with arguments.'
+          private_constant :REQUIRE_MSG
+
+          private
+
+          def require_parentheses(node)
             return if ignored_method?(node.method_name)
             return if matches_ignored_pattern?(node.method_name)
             return if eligible_for_parentheses_omission?(node)
             return unless node.arguments? && !node.parenthesized?
 
-            add_offense(node) do |corrector|
+            add_offense(node, message: REQUIRE_MSG) do |corrector|
               corrector.replace(args_begin(node), '(')
 
               corrector.insert_after(args_end(node), ')') unless args_parenthesized?(node)
             end
           end
-          alias on_csend on_send
-          alias on_super on_send
-          alias on_yield on_send
-
-          def message(_node = nil)
-            'Use parentheses for method calls with arguments.'
-          end
-
-          private
 
           def eligible_for_parentheses_omission?(node)
             node.operator_method? || node.setter_method? || ignored_macro?(node)