[Fix #7999] Consider only the comments relevant for the node being ch…

…ecked

changelog/fix_comment_handling_when_allow_comments_is_true.md

@@ -0,0 +1 @@
+* [#10491](https://github.com/rubocop/rubocop/pull/10491): Improve the handling of comments in `Lint/EmptyConditionalBody`, `Lint/EmptyInPattern` and `Lint/EmptyWhen` when `AllowComments` is set to `true`. ([@Darhazer][])

lib/rubocop/cop/lint/empty_conditional_body.rb

@@ -53,11 +53,13 @@ module Lint
       #   end
       #
       class EmptyConditionalBody < Base
+        include CommentsHelp
+
         MSG = 'Avoid `%<keyword>s` branches without a body.'
 
         def on_if(node)
           return if node.body
-          return if cop_config['AllowComments'] && comment_lines?(node)
+          return if cop_config['AllowComments'] && contains_comments?(node)
 
           add_offense(node, message: format(MSG, keyword: node.keyword))
         end

lib/rubocop/cop/lint/empty_in_pattern.rb

@@ -44,14 +44,16 @@ module Lint
       #
       class EmptyInPattern < Base
         extend TargetRubyVersion
+        include CommentsHelp
 
         MSG = 'Avoid `in` branches without a body.'
 
         minimum_target_ruby_version 2.7
 
         def on_case_match(node)
           node.in_pattern_branches.each do |branch|
-            next if branch.body || (cop_config['AllowComments'] && comment_lines?(node))
+            next if branch.body
+            next if cop_config['AllowComments'] && contains_comments?(branch)
 
             add_offense(branch)
           end

lib/rubocop/cop/lint/empty_when.rb

@@ -45,12 +45,14 @@ module Lint
       #   end
       #
       class EmptyWhen < Base
+        include CommentsHelp
+
         MSG = 'Avoid `when` branches without a body.'
 
         def on_case(node)
           node.each_when do |when_node|
             next if when_node.body
-            next if cop_config['AllowComments'] && comment_lines?(node)
+            next if cop_config['AllowComments'] && contains_comments?(when_node)
 
             add_offense(when_node)
           end

lib/rubocop/cop/mixin/comments_help.rb

@@ -4,15 +4,20 @@ module RuboCop
   module Cop
     # Help methods for working with nodes containing comments.
     module CommentsHelp
-      include VisibilityHelp
-
       def source_range_with_comment(node)
         begin_pos = begin_pos_with_comment(node)
         end_pos = end_position_for(node)
 
         Parser::Source::Range.new(buffer, begin_pos, end_pos)
       end
 
+      def contains_comments?(node)
+        start_line = node.source_range.line
+        end_line = find_end_line(node)
+
+        processed_source.each_comment_in_lines(start_line...end_line).any?
+      end
+
       private
 
       def end_position_for(node)
@@ -37,6 +42,21 @@ def start_line_position(node)
       def buffer
         processed_source.buffer
       end
+
+      # Returns the end line of a node, which might be a comment and not part of the AST
+      # End line is considered either the line at which another node starts, or
+      # the line at which the parent node ends.
+      def find_end_line(node)
+        if node.if_type? && node.loc.else
+          node.loc.else.line
+        elsif (next_sibling = node.right_sibling)
+          next_sibling.loc.line
+        elsif (parent = node.parent)
+          parent.loc.end.line
+        else
+          node.loc.end.line
+        end
+      end
     end
   end
 end

spec/rubocop/cop/lint/empty_conditional_body_spec.rb

@@ -39,6 +39,29 @@
     RUBY
   end
 
+  it 'registers an offense for missing `elsif` body that is not the one with a comment' do
+    expect_offense(<<~RUBY)
+      if condition
+        do_something
+      elsif other_condition
+      ^^^^^^^^^^^^^^^^^^^^^ Avoid `elsif` branches without a body.
+      else
+        # noop
+      end
+    RUBY
+  end
+
+  it 'does not register an offense for missing `elsif` body with an inline comment' do
+    expect_no_offenses(<<~RUBY)
+      if condition
+        do_something
+      elsif other_condition # no op, but avoid going into the else
+      else
+        do_other_things
+      end
+    RUBY
+  end
+
   it 'registers an offense for missing `unless` body' do
     expect_offense(<<~RUBY)
       unless condition

spec/rubocop/cop/lint/empty_in_pattern_spec.rb

@@ -133,6 +133,17 @@
   context 'when `AllowComments: true`', :ruby27 do
     let(:cop_config) { { 'AllowComments' => true } }
 
+    it 'registers an offense for empty `in` when comment is in another branch' do
+      expect_offense(<<~RUBY)
+        case condition
+        in [a]
+        ^^^^^^ Avoid `in` branches without a body.
+        in [a, b]
+          # do nothing
+        end
+      RUBY
+    end
+
     it 'accepts an empty `in` body with a comment' do
       expect_no_offenses(<<~RUBY)
         case condition

spec/rubocop/cop/lint/empty_when_spec.rb

@@ -172,6 +172,29 @@
         end
       RUBY
     end
+
+    it 'registers an offense for missing when body without a comment' do
+      expect_offense(<<~RUBY)
+        case condition
+        when foo
+          42 # magic number
+        when bar
+        ^^^^^^^^ Avoid `when` branches without a body.
+        when baz # more comments mixed
+          21 # another magic number
+        end
+      RUBY
+    end
+
+    it 'accepts an empty when ... then body with a comment' do
+      expect_no_offenses(<<~RUBY)
+        case condition
+        when foo
+          do_something
+        when bar then # do nothing
+        end
+      RUBY
+    end
   end
 
   context 'when `AllowComments: false`' do