Fix a false-positive for Rails/RootPathnameMethods on Ruby 2.4 or lower

Author: r7kamura

changelog/fix_a_false_positive_for_rails_root_pathname_methods_on_ruby_2_4.md

@@ -0,0 +1 @@
+* [#1004](https://github.com/rubocop/rubocop-rails/pull/1004): Fix a false-positive for `Rails/RootPathnameMethods` on Ruby 2.4 or lower. ([@r7kamura][])

lib/rubocop/cop/rails/root_pathname_methods.rb

@@ -32,13 +32,28 @@ module Rails
       #   Rails.root.join('db', 'schema.rb').write(content)
       #   Rails.root.join('db', 'schema.rb').binwrite(content)
       #
-      class RootPathnameMethods < Base
+      class RootPathnameMethods < Base # rubocop:disable Metrics/ClassLength
         extend AutoCorrector
         include RangeHelp
 
         MSG = '`%<rails_root>s` is a `Pathname` so you can just append `#%<method>s`.'
 
-        DIR_METHODS = %i[children delete each_child empty? entries exist? glob mkdir open rmdir unlink].to_set.freeze
+        DIR_GLOB_METHODS = %i[glob].to_set.freeze
+
+        DIR_NON_GLOB_METHODS = %i[
+          children
+          delete
+          each_child
+          empty?
+          entries
+          exist?
+          mkdir
+          open
+          rmdir
+          unlink
+        ].to_set.freeze
+
+        DIR_METHODS = (DIR_GLOB_METHODS + DIR_NON_GLOB_METHODS).freeze
 
         FILE_METHODS = %i[
           atime
@@ -134,7 +149,8 @@ class RootPathnameMethods < Base
 
         RESTRICT_ON_SEND = (DIR_METHODS + FILE_METHODS + FILE_TEST_METHODS + FILE_UTILS_METHODS).to_set.freeze
 
-        def_node_matcher :pathname_method, <<~PATTERN
+        # @!method pathname_method_for_ruby_2_5_or_higher(node)
+        def_node_matcher :pathname_method_for_ruby_2_5_or_higher, <<~PATTERN
           {
             (send (const {nil? cbase} :Dir) $DIR_METHODS $_ $...)
             (send (const {nil? cbase} {:IO :File}) $FILE_METHODS $_ $...)
@@ -143,6 +159,16 @@ class RootPathnameMethods < Base
           }
         PATTERN
 
+        # @!method pathname_method_for_ruby_2_4_or_lower(node)
+        def_node_matcher :pathname_method_for_ruby_2_4_or_lower, <<~PATTERN
+          {
+            (send (const {nil? cbase} :Dir) $DIR_NON_GLOB_METHODS $_ $...)
+            (send (const {nil? cbase} {:IO :File}) $FILE_METHODS $_ $...)
+            (send (const {nil? cbase} :FileTest) $FILE_TEST_METHODS $_ $...)
+            (send (const {nil? cbase} :FileUtils) $FILE_UTILS_METHODS $_ $...)
+          }
+        PATTERN
+
         def_node_matcher :dir_glob?, <<~PATTERN
           (send
             (const {cbase nil?} :Dir) :glob ...)
@@ -183,6 +209,14 @@ def evidence(node)
           yield(method, path, args, rails_root)
         end
 
+        def pathname_method(node)
+          if target_ruby_version >= 2.5
+            pathname_method_for_ruby_2_5_or_higher(node)
+          else
+            pathname_method_for_ruby_2_4_or_lower(node)
+          end
+        end
+
         def build_path_glob_replacement(path, method)
           receiver = range_between(path.source_range.begin_pos, path.children.first.loc.selector.end_pos).source
 

spec/rubocop/cop/rails/root_pathname_methods_spec.rb

@@ -46,7 +46,15 @@
     end
   end
 
-  context 'when using `Dir.glob`' do
+  context 'when using `Dir.glob` on Ruby 2.4 or lower', :ruby24 do
+    it 'does not registers an offense' do
+      expect_no_offenses(<<~RUBY)
+        Dir.glob(Rails.root.join('**/*.rb'))
+      RUBY
+    end
+  end
+
+  context 'when using `Dir.glob` on Ruby 2.5 or higher', :ruby25 do
     it "registers an offense when using `Dir.glob(Rails.root.join('**/*.rb'))`" do
       expect_offense(<<~RUBY)
         Dir.glob(Rails.root.join('**/*.rb'))