Add new Style/RedundantHeredocDelimiterQuotes cop

Follow up #11522 (comment).

This cop checks for redundant heredoc delimiter quotes.

```ruby
# bad
do_something(<<~'EOS')
  no string interpolation style text
EOS

# good
do_something(<<~EOS)
  no string interpolation style text
EOS
```

changelog/new_add_new_style_redundant_heredoc_delimiter_quotes_cop.md

@@ -0,0 +1 @@
+* [#11528](https://github.com/rubocop/rubocop/pull/11528): Add new `Style/RedundantHeredocDelimiterQuotes` cop. ([@koic][])

config/default.yml

@@ -4843,6 +4843,11 @@ Style/RedundantFreeze:
   VersionAdded: '0.34'
   VersionChanged: '0.66'
 
+Style/RedundantHeredocDelimiterQuotes:
+  Description: 'Checks for redundant heredoc delimiter quotes.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Style/RedundantInitialize:
   Description: 'Checks for redundant `initialize` methods.'
   Enabled: pending

lib/rubocop.rb

@@ -556,6 +556,7 @@
 require_relative 'rubocop/cop/style/redundant_each'
 require_relative 'rubocop/cop/style/redundant_fetch_block'
 require_relative 'rubocop/cop/style/redundant_file_extension_in_require'
+require_relative 'rubocop/cop/style/redundant_heredoc_delimiter_quotes'
 require_relative 'rubocop/cop/style/redundant_initialize'
 require_relative 'rubocop/cop/style/redundant_self_assignment'
 require_relative 'rubocop/cop/style/redundant_self_assignment_branch'

lib/rubocop/cop/style/redundant_heredoc_delimiter_quotes.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # Checks for redundant heredoc delimiter quotes.
+      #
+      # @example
+      #
+      #   # bad
+      #   do_something(<<~'EOS')
+      #     no string interpolation style text
+      #   EOS
+      #
+      #   # good
+      #   do_something(<<~EOS)
+      #     no string interpolation style text
+      #   EOS
+      #
+      #   do_something(<<~'EOS')
+      #     #{string_interpolation_style_text_not_evaluated}
+      #   EOS
+      #
+      #   do_something(<<~'EOS')
+      #     escaped character\.
+      #   EOS
+      #
+      class RedundantHeredocDelimiterQuotes < Base
+        include Heredoc
+        extend AutoCorrector
+
+        MSG = 'Remove the redundant heredoc delimiter quotes, use `%<replacement>s` instead.'
+        STRING_INTERPOLATION_OR_ESCAPED_CHARACTER_PATTERN = /#(\{|@|\$)|\\/.freeze
+
+        def on_heredoc(node)
+          return if need_heredoc_delimiter_quotes?(node)
+
+          replacement = "#{heredoc_type(node)}#{delimiter_string(node)}"
+
+          add_offense(node, message: format(MSG, replacement: replacement)) do |corrector|
+            corrector.replace(node, replacement)
+          end
+        end
+
+        private
+
+        def need_heredoc_delimiter_quotes?(node)
+          heredoc_delimiter = node.source.delete(heredoc_type(node))
+          return true unless heredoc_delimiter.start_with?("'", '"')
+
+          node.loc.heredoc_end.source.strip.match?(/\W/) ||
+            node.loc.heredoc_body.source.match?(STRING_INTERPOLATION_OR_ESCAPED_CHARACTER_PATTERN)
+        end
+      end
+    end
+  end
+end

spec/rubocop/cli/autocorrect_spec.rb

@@ -716,12 +716,12 @@ def method
   end
 
   it 'corrects Style/InverseMethods and Style/Not offenses' do
-    source = <<~'RUBY'
+    source = <<~RUBY
       x.select {|y| not y.z }
     RUBY
     create_file('example.rb', source)
     expect(cli.run(['--autocorrect-all', '--only', 'Style/InverseMethods,Style/Not'])).to eq(0)
-    corrected = <<~'RUBY'
+    corrected = <<~RUBY
       x.reject {|y|  y.z }
     RUBY
     expect(File.read('example.rb')).to eq(corrected)
@@ -732,7 +732,7 @@ def method
       AllCops:
         TargetRubyVersion: 2.6
     YAML
-    source = <<~'RUBY'
+    source = <<~RUBY
       until x
         if foo
           foo.some_method do
@@ -743,7 +743,7 @@ def method
     RUBY
     create_file('example.rb', source)
     expect(cli.run(['--autocorrect-all', '--only', 'Style/Next,Style/SafeNavigation'])).to eq(0)
-    corrected = <<~'RUBY'
+    corrected = <<~RUBY
       until x
         next unless foo
         foo.some_method do
@@ -755,7 +755,7 @@ def method
   end
 
   it 'corrects `Lint/Lambda` and `Lint/UnusedBlockArgument` offenses' do
-    source = <<~'RUBY'
+    source = <<~RUBY
       c = -> event do
         puts 'Hello world'
       end
@@ -765,7 +765,7 @@ def method
                      '--autocorrect-all',
                      '--only', 'Lint/Lambda,Lint/UnusedBlockArgument'
                    ])).to eq(0)
-    corrected = <<~'RUBY'
+    corrected = <<~RUBY
       c = lambda do |_event|
         puts 'Hello world'
       end
@@ -1100,7 +1100,7 @@ def method
         EnforcedStyle: indented_internal_methods
     YAML
 
-    source = <<~'RUBY'
+    source = <<~RUBY
       class Foo
                          private
 
@@ -1121,7 +1121,7 @@ def do_something
                      ].join(',')
                    ])).to eq(0)
 
-    corrected = <<~'RUBY'
+    corrected = <<~RUBY
       class Foo
       private
 
@@ -1135,7 +1135,7 @@ def do_something
 
   it 'corrects IndentationWidth and IndentationConsistency offenses' \
      'without correcting `Style/TrailingBodyOnClass`' do
-    source = <<~'RUBY'
+    source = <<~RUBY
       class Test foo
           def func1
           end
@@ -1151,7 +1151,7 @@ def func2
                      ['Layout/IndentationConsistency', 'Layout/IndentationWidth'].join(',')
                    ])).to eq(0)
 
-    corrected = <<~'RUBY'
+    corrected = <<~RUBY
       class Test foo
                  def func1
                  end

spec/rubocop/config_loader_spec.rb

@@ -786,7 +786,7 @@ def enabled?(cop)
           end
 
           if custom_dept_to_disable == 'Foo'
-            message = <<~'OUTPUT'.chomp
+            message = <<~OUTPUT.chomp
               unrecognized cop or department Foo found in parent_rubocop.yml
               Foo is not a department. Use `Foo/Bar`.
             OUTPUT

spec/rubocop/cop/layout/class_structure_spec.rb

@@ -363,7 +363,7 @@ def do_something
   end
 
   it 'registers an offense and corrects when xstr heredoc constant is defined after public method' do
-    expect_offense(<<~'RUBY')
+    expect_offense(<<~RUBY)
       class Foo
         def do_something
         end
@@ -375,7 +375,7 @@ def do_something
       end
     RUBY
 
-    expect_correction(<<~'RUBY')
+    expect_correction(<<~RUBY)
       class Foo
         CONSTANT = <<~`EOS`
           str

spec/rubocop/cop/layout/dot_position_spec.rb

@@ -234,7 +234,7 @@
 
       context 'with multiple heredocs' do
         it 'registers an offense' do
-          expect_offense(<<~'RUBY')
+          expect_offense(<<~RUBY)
             my_method.
                      ^ Place the . on the next line, together with the method name.
               something(<<~HERE, <<~THERE).
@@ -246,7 +246,7 @@
               somethingelse
           RUBY
 
-          expect_correction(<<~'RUBY')
+          expect_correction(<<~RUBY)
             my_method
               .something(<<~HERE, <<~THERE)
                 something
@@ -440,7 +440,7 @@
 
       context 'with multiple heredocs' do
         it 'registers an offense' do
-          expect_offense(<<~'RUBY')
+          expect_offense(<<~RUBY)
             my_method
               .something(<<~HERE, <<~THERE)
               ^ Place the . on the previous line, together with the method call receiver.
@@ -452,7 +452,7 @@
               ^ Place the . on the previous line, together with the method call receiver.
           RUBY
 
-          expect_correction(<<~'RUBY')
+          expect_correction(<<~RUBY)
             my_method.
               something(<<~HERE, <<~THERE).
                 something

spec/rubocop/cop/layout/else_alignment_spec.rb

@@ -400,7 +400,7 @@
         end
 
         it 'accepts case match without else' do
-          expect_no_offenses(<<~'RUBY')
+          expect_no_offenses(<<~RUBY)
             case 0
             in a
               p a

spec/rubocop/cop/layout/empty_line_after_guard_clause_spec.rb

@@ -137,7 +137,7 @@ def foo
 
   it 'accepts a `raise` guard clause not followed by empty line when guard ' \
      'clause is after condition without method invocation' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       def foo
         raise unless $1 == o
 

spec/rubocop/cop/layout/indentation_consistency_spec.rb

@@ -11,7 +11,7 @@
     end
 
     it 'accepts when using access modifier at the top level' do
-      expect_no_offenses(<<~'RUBY')
+      expect_no_offenses(<<~RUBY)
         public
 
         def foo
@@ -21,15 +21,15 @@ def foo
 
     it 'registers and corrects an offense when using access modifier and indented method definition ' \
        'at the top level' do
-      expect_offense(<<~'RUBY')
+      expect_offense(<<~RUBY)
         public
 
           def foo
           ^^^^^^^ Inconsistent indentation detected.
           end
       RUBY
 
-      expect_correction(<<~'RUBY')
+      expect_correction(<<~RUBY)
         public
 
         def foo

spec/rubocop/cop/layout/indentation_width_spec.rb

@@ -905,7 +905,7 @@ def x
       end
 
       it 'accepts aligned values in `in` clause' do
-        expect_no_offenses(<<~'RUBY')
+        expect_no_offenses(<<~RUBY)
           case condition
           in [42]
             foo
@@ -916,7 +916,7 @@ def x
       end
 
       it 'accepts aligned value in `in` clause and `else` is empty' do
-        expect_no_offenses(<<~'RUBY')
+        expect_no_offenses(<<~RUBY)
           case x
           in 42
             foo

spec/rubocop/cop/layout/leading_comment_space_spec.rb

@@ -168,7 +168,7 @@
       let(:cop_config) { { 'AllowGemfileRubyComment' => false } }
 
       it 'registers an offense when using ruby config as comment' do
-        expect_offense(<<~'RUBY')
+        expect_offense(<<~RUBY)
           # Specific version (comment) will be used by RVM
           #ruby=2.7.0
           ^^^^^^^^^^^ Missing space after `#`.
@@ -184,7 +184,7 @@
 
       context 'file not named Gemfile' do
         it 'registers an offense when using ruby config as comment' do
-          expect_offense(<<~'RUBY', 'test/test_case.rb')
+          expect_offense(<<~RUBY, 'test/test_case.rb')
             # Specific version (comment) will be used by RVM
             #ruby=2.7.0
             ^^^^^^^^^^^ Missing space after `#`.
@@ -197,7 +197,7 @@
 
       context 'file named Gemfile' do
         it 'does not register an offense when using ruby config as comment' do
-          expect_no_offenses(<<~'RUBY', 'Gemfile')
+          expect_no_offenses(<<~RUBY, 'Gemfile')
             # Specific version (comment) will be used by RVM
             #ruby=2.7.0
             #ruby-gemset=myproject

spec/rubocop/cop/layout/line_end_string_concatenation_indentation_spec.rb

@@ -31,7 +31,7 @@
     end
 
     it 'accepts a multiline string literal' do
-      expect_no_offenses(<<~'RUBY')
+      expect_no_offenses(<<~RUBY)
         puts %(
           foo
           bar
@@ -128,7 +128,7 @@ def some_method
     end
 
     it 'accepts a heredoc string ...' do
-      expect_no_offenses(<<~'RUBY')
+      expect_no_offenses(<<~RUBY)
         let(:source) do
           <<~CODE
             func({
@@ -152,7 +152,7 @@ def some_method
     end
 
     it 'accepts an empty heredoc string with interpolation' do
-      expect_no_offenses(<<~'RUBY')
+      expect_no_offenses(<<~RUBY)
         puts(<<~TEXT)
         TEXT
       RUBY

spec/rubocop/cop/layout/space_inside_parens_spec.rb

@@ -22,7 +22,7 @@
     end
 
     it 'registers an offense for space around heredoc start' do
-      expect_offense(<<~'RUBY')
+      expect_offense(<<~RUBY)
         f( <<~HEREDOC )
                      ^ Space inside parentheses detected.
           ^ Space inside parentheses detected.

spec/rubocop/cop/lint/empty_interpolation_spec.rb

@@ -7,7 +7,7 @@
                    ^^^ Empty interpolation detected.
     RUBY
 
-    expect_correction(<<~'RUBY')
+    expect_correction(<<~RUBY)
       "this is the "
     RUBY
   end
@@ -18,7 +18,7 @@
                    ^^^^ Empty interpolation detected.
     RUBY
 
-    expect_correction(<<~'RUBY')
+    expect_correction(<<~RUBY)
       "this is the "
     RUBY
   end

spec/rubocop/cop/lint/mixed_regexp_capture_types_spec.rb

@@ -28,7 +28,7 @@
 
   # See https://github.com/rubocop/rubocop/issues/8083
   it 'does not register offense when using a Regexp cannot be processed by regexp_parser gem' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       /data = ({"words":.+}}}[^}]*})/m
     RUBY
   end