[Fix #8372] Fix Lint/RedundantCopDisableDirective autocorrection re…

…moving a preceding newline incorrectly. (#8744)

There were no tests previously for autocorrection, so this change also adds tests to ensure whitespace is managed correctly.

Co-authored-by: Bozhidar Batsov <bozhidar@batsov.com>

CHANGELOG.md

@@ -15,6 +15,7 @@
 * [#8750](https://github.com/rubocop-hq/rubocop/pull/8750): Fix an incorrect auto-correct for `Style/MultilineWhenThen` when line break for multiple condidate values of `when` statement. ([@koic][])
 * [#8754](https://github.com/rubocop-hq/rubocop/pull/8754): Fix an error for `Style/RandomWithOffset` when using a range with non-integer bounds. ([@eugeneius][])
 * [#8756](https://github.com/rubocop-hq/rubocop/issues/8756): Fix an infinite loop error for `Layout/EmptyLinesAroundAccessModifier` with `Layout/EmptyLinesAroundBlockBody` when using access modifier with block argument. ([@koic][])
+* [#8372](https://github.com/rubocop-hq/rubocop/issues/8372): Fix `Lint/RedundantCopDisableDirective` autocorrection. ([@dvandersluis][])
 * [#8764](https://github.com/rubocop-hq/rubocop/issues/8764): Fix `Layout/CaseIndentation` not showing the cop name in output messages. ([@dvandersluis][])
 * [#8771](https://github.com/rubocop-hq/rubocop/issues/8771): Fix an error for `Style/OneLineConditional` when using `if-then-elsif-then-end`. ([@koic][])
 * [#8576](https://github.com/rubocop-hq/rubocop/issues/8576): Fix `Style/IfUnlessModifier` to ignore cop disable comment directives when considering conversion to the modifier form. ([@dsavochkin][])

lib/rubocop/cop/lint/redundant_cop_disable_directive.rb

@@ -56,19 +56,29 @@ def on_new_investigation
 
         private
 
+        def previous_line_blank?(range)
+          processed_source.buffer.source_line(range.line - 1).blank?
+        end
+
         def comment_range_with_surrounding_space(range)
-          # Eat the entire comment, the preceding space, and the preceding
-          # newline if there is one.
-          original_begin = range.begin_pos
-          range = range_with_surrounding_space(range: range,
-                                               side: :left,
-                                               newlines: true)
-          range_with_surrounding_space(range: range,
-                                       side: :right,
-                                       # Special for a comment that
-                                       # begins the file: remove
-                                       # the newline at the end.
-                                       newlines: original_begin.zero?)
+          if previous_line_blank?(range)
+            # When the previous line is blank, it should be retained
+            range_with_surrounding_space(range: range, side: :right)
+          else
+            # Eat the entire comment, the preceding space, and the preceding
+            # newline if there is one.
+            original_begin = range.begin_pos
+            range = range_with_surrounding_space(range: range,
+                                                 side: :left,
+                                                 newlines: true)
+
+            range_with_surrounding_space(range: range,
+                                         side: :right,
+                                         # Special for a comment that
+                                         # begins the file: remove
+                                         # the newline at the end.
+                                         newlines: original_begin.zero?)
+          end
         end
 
         def directive_range_in_list(range, ranges)

spec/rubocop/cop/lint/redundant_cop_disable_directive_spec.rb

@@ -314,5 +314,157 @@ class One
         end
       end
     end
+
+    context 'autocorrecting whitespace' do
+      context 'when the comment is the first line of the file' do
+        context 'followed by code' do
+          it 'removes the comment' do
+            expect_offense(<<~RUBY)
+              # rubocop:disable Metrics/MethodLength
+              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/MethodLength`.
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+
+            expect_correction(<<~RUBY)
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+          end
+        end
+
+        context 'followed by a newline' do
+          it 'removes the comment and newline' do
+            expect_offense(<<~RUBY)
+              # rubocop:disable Metrics/MethodLength
+              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/MethodLength`.
+
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+
+            expect_correction(<<~RUBY)
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+          end
+        end
+
+        context 'followed by another comment' do
+          it 'removes the comment and newline' do
+            expect_offense(<<~RUBY)
+              # rubocop:disable Metrics/MethodLength
+              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/MethodLength`.
+              # @api private
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+
+            expect_correction(<<~RUBY)
+              # @api private
+              def my_method
+              end
+              # rubocop:enable Metrics/MethodLength
+            RUBY
+          end
+        end
+      end
+
+      context 'when there is only whitespace before the comment' do
+        it 'leaves the whitespace' do
+          expect_offense(<<~RUBY)
+
+            # rubocop:disable Metrics/MethodLength
+            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/MethodLength`.
+            def my_method
+            end
+            # rubocop:enable Metrics/MethodLength
+          RUBY
+
+          expect_correction(<<~RUBY)
+
+            def my_method
+            end
+            # rubocop:enable Metrics/MethodLength
+          RUBY
+        end
+      end
+
+      context 'when the comment is not the first line of the file' do
+        it 'preserves whitespace before the comment' do
+          expect_offense(<<~RUBY)
+            attr_reader :foo
+
+            # rubocop:disable Metrics/MethodLength
+            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/MethodLength`.
+            def my_method
+            end
+            # rubocop:enable Metrics/MethodLength
+          RUBY
+
+          expect_correction(<<~RUBY)
+            attr_reader :foo
+
+            def my_method
+            end
+            # rubocop:enable Metrics/MethodLength
+          RUBY
+        end
+      end
+
+      context 'nested inside a namespace' do
+        it 'preserves indentation' do
+          expect_offense(<<~RUBY)
+            module Foo
+              module Bar
+                # rubocop:disable Metrics/ClassLength
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/ClassLength`.
+                class Baz
+                end
+                # rubocop:enable Metrics/ClassLength
+              end
+            end
+          RUBY
+
+          expect_correction(<<~RUBY)
+            module Foo
+              module Bar
+                class Baz
+                end
+                # rubocop:enable Metrics/ClassLength
+              end
+            end
+          RUBY
+        end
+      end
+
+      context 'inline comment' do
+        it 'removes the comment and preceding whitespace' do
+          expect_offense(<<~RUBY)
+            module Foo
+              module Bar
+                class Baz         # rubocop:disable Metrics/ClassLength
+                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Unnecessary disabling of `Metrics/ClassLength`.
+                end
+              end
+            end
+          RUBY
+
+          expect_correction(<<~RUBY)
+            module Foo
+              module Bar
+                class Baz
+                end
+              end
+            end
+          RUBY
+        end
+      end
+    end
   end
 end