From cfdb0a1e67f1d29cee79e8aa09c900239fbb4a6a Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 6 Jul 2021 01:43:33 +0900
Subject: [PATCH] [Fix #9902] Fix an incorrect auto-correct for
 `Style/BlockDelimiters`

Fixes #9902

This PR fixes an incorrect auto-correct for `Style/BlockDelimiters`
when there is a comment after the closing brace.
It prevents `Style/CommentedKeyword` from removing source code
comment after `end` keyword.
---
 .rubocop_todo.yml                             |  2 +-
 ..._autocorrect_for_style_block_delimiters.md |  1 +
 lib/rubocop/cop/style/block_delimiters.rb     | 15 ++++++++++
 spec/rubocop/cli/autocorrect_spec.rb          | 22 ++++++++++++++
 .../cop/style/block_delimiters_spec.rb        | 29 +++++++++++++++++++
 5 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 changelog/fix_incorrect_autocorrect_for_style_block_delimiters.md

diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index ca611c6366b..86dca796768 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -13,7 +13,7 @@ InternalAffairs/NodeDestructuring:
 # Offense count: 49
 # Configuration parameters: CountComments, CountAsOne.
 Metrics/ClassLength:
-  Max: 186
+  Max: 196
 
 # Offense count: 228
 # Configuration parameters: CountComments, CountAsOne, ExcludedMethods, IgnoredMethods.
diff --git a/changelog/fix_incorrect_autocorrect_for_style_block_delimiters.md b/changelog/fix_incorrect_autocorrect_for_style_block_delimiters.md
new file mode 100644
index 00000000000..bc5310cf89d
--- /dev/null
+++ b/changelog/fix_incorrect_autocorrect_for_style_block_delimiters.md
@@ -0,0 +1 @@
+* [#9902](https://github.com/rubocop/rubocop/issues/9902): Fix an incorrect auto-correct for `Style/BlockDelimiters` when there is a comment after the closing brace. ([@koic][])
diff --git a/lib/rubocop/cop/style/block_delimiters.rb b/lib/rubocop/cop/style/block_delimiters.rb
index d8b80988a95..42251584dd8 100644
--- a/lib/rubocop/cop/style/block_delimiters.rb
+++ b/lib/rubocop/cop/style/block_delimiters.rb
@@ -135,6 +135,7 @@ module Style
       class BlockDelimiters < Base
         include ConfigurableEnforcedStyle
         include IgnoredMethods
+        include RangeHelp
         extend AutoCorrector
 
         ALWAYS_BRACES_MESSAGE = 'Prefer `{...}` over `do...end` for blocks.'
@@ -231,6 +232,11 @@ def replace_braces_with_do_end(corrector, loc)
           corrector.insert_before(e, ' ') unless whitespace_before?(e)
           corrector.insert_after(b, ' ') unless whitespace_after?(b)
           corrector.replace(b, 'do')
+
+          if (comment = processed_source.comment_at_line(e.line))
+            move_comment_before_block(corrector, comment, loc.node, e)
+          end
+
           corrector.replace(e, 'end')
         end
 
@@ -252,6 +258,15 @@ def whitespace_after?(range, length = 1)
           /\s/.match?(range.source_buffer.source[range.begin_pos + length, 1])
         end
 
+        def move_comment_before_block(corrector, comment, block_node, closing_brace)
+          range = range_between(closing_brace.end_pos, comment.loc.expression.end_pos)
+
+          corrector.remove(range_with_surrounding_space(range: range, side: :right))
+          corrector.insert_after(closing_brace, "\n")
+
+          corrector.insert_before(block_node, "#{comment.text}\n")
+        end
+
         def get_blocks(node, &block)
           case node.type
           when :block
diff --git a/spec/rubocop/cli/autocorrect_spec.rb b/spec/rubocop/cli/autocorrect_spec.rb
index fc35d83767c..0ffc39c3100 100644
--- a/spec/rubocop/cli/autocorrect_spec.rb
+++ b/spec/rubocop/cli/autocorrect_spec.rb
@@ -196,6 +196,28 @@ def batch
     RUBY
   end
 
+  it 'corrects `EnforcedStyle: line_count_based` of `Style/BlockDelimiters` with `Style/CommentedKeyword` and `Layout/BlockEndNewline`' do
+    create_file('.rubocop.yml', <<~YAML)
+      Style/BlockDelimiters:
+        EnforcedStyle: line_count_based
+    YAML
+    source = <<~RUBY
+      foo {
+      bar } # This comment should be kept.
+    RUBY
+    create_file('example.rb', source)
+    expect(cli.run([
+                     '--auto-correct',
+                     '--only', 'Style/BlockDelimiters,Style/CommentedKeyword,Layout/BlockEndNewline'
+                   ])).to eq(0)
+    expect(File.read('example.rb')).to eq(<<~RUBY)
+      # This comment should be kept.
+      foo do
+      bar
+      end
+    RUBY
+  end
+
   it 'corrects `EnforcedStyle: require_parentheses` of `Style/MethodCallWithArgsParentheses` with `Style/NestedParenthesizedCalls`' do
     create_file('.rubocop.yml', <<~YAML)
       Style/MethodCallWithArgsParentheses:
diff --git a/spec/rubocop/cop/style/block_delimiters_spec.rb b/spec/rubocop/cop/style/block_delimiters_spec.rb
index 9f74fb8954f..bc51589c65e 100644
--- a/spec/rubocop/cop/style/block_delimiters_spec.rb
+++ b/spec/rubocop/cop/style/block_delimiters_spec.rb
@@ -354,6 +354,35 @@
         RUBY
       end
 
+      it 'registers an offense when there is a comment after the closing brace and block body is not empty' do
+        expect_offense(<<~RUBY)
+          baz.map { |x|
+                  ^ Avoid using `{...}` for multi-line blocks.
+          foo(x) } # comment
+        RUBY
+
+        expect_correction(<<~RUBY)
+          # comment
+          baz.map do |x|
+          foo(x) end
+        RUBY
+      end
+
+      it 'registers an offense when there is a comment after the closing brace and block body is empty' do
+        expect_offense(<<~RUBY)
+          baz.map { |x|
+                  ^ Avoid using `{...}` for multi-line blocks.
+          } # comment
+
+        RUBY
+
+        expect_correction(<<~RUBY)
+          # comment
+          baz.map do |x|
+          end
+        RUBY
+      end
+
       it 'accepts braces if do-end would change the meaning' do
         expect_no_offenses(<<~RUBY)
           scope :foo, lambda { |f|