Fix false negatives when public method is defined after a private one

changelog/fix_false_negatives_in_documentation_comment.md

@@ -0,0 +1 @@
+* [#10774](https://github.com/rubocop/rubocop/pull/10774): Fix false negatives in `Style/DocumentationMethod` when a public method is defined after a private one. ([@Darhazer][])

lib/rubocop.rb

@@ -72,7 +72,6 @@
 require_relative 'rubocop/cop/mixin/configurable_formatting'
 require_relative 'rubocop/cop/mixin/configurable_naming'
 require_relative 'rubocop/cop/mixin/configurable_numbering'
-require_relative 'rubocop/cop/mixin/def_node'
 require_relative 'rubocop/cop/mixin/documentation_comment'
 require_relative 'rubocop/cop/mixin/duplication'
 require_relative 'rubocop/cop/mixin/range_help'
@@ -130,6 +129,7 @@
 require_relative 'rubocop/cop/mixin/unused_argument'
 require_relative 'rubocop/cop/mixin/visibility_help'
 require_relative 'rubocop/cop/mixin/comments_help' # relies on visibility_help
+require_relative 'rubocop/cop/mixin/def_node' # relies on visibility_help
 
 require_relative 'rubocop/cop/utils/format_string'
 

lib/rubocop/cop/mixin/def_node.rb

@@ -5,8 +5,7 @@ module Cop
     # Common functionality for checking def nodes.
     module DefNode
       extend NodePattern::Macros
-
-      NON_PUBLIC_MODIFIERS = %w[private protected].freeze
+      include VisibilityHelp
 
       private
 
@@ -15,11 +14,7 @@ def non_public?(node)
       end
 
       def preceding_non_public_modifier?(node)
-        stripped_source_upto(node.first_line).any? { |line| NON_PUBLIC_MODIFIERS.include?(line) }
-      end
-
-      def stripped_source_upto(index)
-        processed_source[0..index].map(&:strip)
+        node_visibility(node) != :public
       end
 
       # @!method non_public_modifier?(node)

spec/rubocop/cop/style/documentation_method_spec.rb

@@ -32,6 +32,24 @@ def method; end
             ^^^^^^^^^^^^^^^ Missing method documentation comment.
           CODE
         end
+
+        it 'registers an offense when method is public, but there were private methods before' do
+          expect_offense(<<~CODE)
+            class Foo
+                private
+
+                def baz
+                end
+
+                public
+
+                def foo
+                ^^^^^^^ Missing method documentation comment.
+                  puts 'bar'
+                end
+            end
+          CODE
+        end
       end
 
       context 'when method is private' do