Include line continuations in whitespace for NestedParenthesizedCalls

Include backslash followed by newline as whitespace when replacing with
parentheses in Style/NestedParenthesizedCalls cop.

Fix existing spec for:

```ruby
puts(nex \
       5)
```

to auto-correct to:

```ruby
puts(nex(5))
```

Originally the spec was written such that the backslash newline gets
interpreted when parsing the heredoc as:

```ruby
"puts(nex        5)\n"
```

CHANGELOG.md

@@ -53,6 +53,7 @@
 * [#8226](https://github.com/rubocop-hq/rubocop/issues/8226): Fix `Style/IfUnlessModifier` to add parentheses when converting if-end condition inside an array or a hash to a single-line form. ([@dsavochkin][])
 * [#8443](https://github.com/rubocop-hq/rubocop/pull/8443): Fix an incorrect auto-correct for `Style/StructInheritance` when there is a comment before class declaration. ([@koic][])
 * [#8444](https://github.com/rubocop-hq/rubocop/issues/8444): Fix an error for `Layout/FirstMethodArgumentLineBreak` when using kwargs in `super`. ([@koic][])
+* [#8448](https://github.com/rubocop-hq/rubocop/pull/8448): Fix `Style/NestedParenthesizedCalls` to include line continuations in whitespace for auto-correct. ([@biinari][])
 
 ### Changes
 

lib/rubocop/cop/mixin/range_help.rb

@@ -46,7 +46,8 @@ def range_with_surrounding_comma(range, side = :both)
       end
 
       def range_with_surrounding_space(range:, side: :both,
-                                       newlines: true, whitespace: false)
+                                       newlines: true, whitespace: false,
+                                       continuations: false)
         buffer = @processed_source.buffer
         src = buffer.source
 
@@ -55,10 +56,13 @@ def range_with_surrounding_space(range:, side: :both,
         begin_pos = range.begin_pos
         if go_left
           begin_pos =
-            final_pos(src, begin_pos, -1, newlines, whitespace)
+            final_pos(src, begin_pos, -1, continuations, newlines, whitespace)
         end
         end_pos = range.end_pos
-        end_pos = final_pos(src, end_pos, 1, newlines, whitespace) if go_right
+        if go_right
+          end_pos =
+            final_pos(src, end_pos, 1, continuations, newlines, whitespace)
+        end
         Parser::Source::Range.new(buffer, begin_pos, end_pos)
       end
 
@@ -101,17 +105,27 @@ def directions(side)
         end
       end
 
-      def final_pos(src, pos, increment, newlines, whitespace)
+      # rubocop:disable Metrics/ParameterLists
+      def final_pos(src, pos, increment, continuations, newlines, whitespace)
         pos = move_pos(src, pos, increment, true, /[ \t]/)
+        pos = move_pos_str(src, pos, increment, continuations, "\\\n")
         pos = move_pos(src, pos, increment, newlines, /\n/)
         move_pos(src, pos, increment, whitespace, /\s/)
       end
+      # rubocop:enable Metrics/ParameterLists
 
       def move_pos(src, pos, step, condition, regexp)
         offset = step == -1 ? -1 : 0
         pos += step while condition && regexp.match?(src[pos + offset])
         pos.negative? ? 0 : pos
       end
+
+      def move_pos_str(src, pos, step, condition, needle)
+        size = needle.length
+        offset = step == -1 ? -size : 0
+        pos += size * step while condition && src[pos + offset, size] == needle
+        pos.negative? ? 0 : pos
+      end
     end
   end
 end

lib/rubocop/cop/style/nested_parenthesized_calls.rb

@@ -37,7 +37,9 @@ def autocorrect(nested)
 
           leading_space =
             range_with_surrounding_space(range: first_arg.begin,
-                                         side: :left)
+                                         side: :left,
+                                         whitespace: true,
+                                         continuations: true)
 
           lambda do |corrector|
             corrector.replace(leading_space, '(')

spec/rubocop/cop/style/nested_parenthesized_calls_spec.rb

@@ -103,7 +103,7 @@
 
   context 'backslash newline in method call' do
     let(:source) do
-      <<~RUBY
+      <<~'RUBY'
         puts(nex \
                5)
       RUBY