[Fix rubocop#7426] Add always_true to Style/FrozenStringLiteralComment

This adds another style to Style/FrozenStringLiteralComment that
enforces that the comment is always enabled, that is, it requires that
string literals are always frozen. The default style, `always`,
enforces that the comment exists but does not enforce that the comment
is enabled.

This also differentiates the offense message for the `always` and
`always_true` styles.

It changes the offense message when using the `always` style to be
less specific, since the old version of the message implied that the
only acceptable value of the frozen_string_literal comment was
`true`. In fact, in the `always` style, either `true` or `false` is
acceptable. The new `always_true` style uses that preexisting message,
since when using that style it is required that the value of the
frozen_string_literal comment is `true`.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### New features
+
+* [#7426](https://github.com/rubocop-hq/rubocop/issues/7426): Add `always_true` style to Style/FrozenStringLiteralComment. ([@parkerfinch][])
+
 ### Bug fixes
 
 * [#7530](https://github.com/rubocop-hq/rubocop/issues/7530): Typo in `Style/TrivialAccessors`'s `AllowedMethods`. ([@movermeyer][])

config/default.yml

@@ -2754,6 +2754,10 @@ Style/FrozenStringLiteralComment:
     # string literal. If you run code against multiple versions of Ruby, it is
     # possible that this will create errors in Ruby 2.3.0+.
     - always
+    # `always_true` will add the frozen string literal comment to a file,
+    # similarly to the `always` style, but will also change any disabled
+    # comments (e.g. `# frozen_string_literal: false`) to be enabled.
+    - always_true
     # `never` will enforce that the frozen string literal comment does not
     # exist in a file.
     - never

lib/rubocop/cop/mixin/frozen_string_literal.rb

@@ -39,6 +39,12 @@ def frozen_string_literals_enabled?
         end
       end
 
+      def frozen_string_literal_specified?
+        leading_comment_lines.any? do |line|
+          MagicComment.parse(line).frozen_string_literal_specified?
+        end
+      end
+
       def leading_comment_lines
         comments = processed_source.comments
 

lib/rubocop/cop/style/frozen_string_literal_comment.rb

@@ -51,29 +51,65 @@ module Style
       #   module Baz
       #     # ...
       #   end
+      #
+      # @example EnforcedStyle: always_true
+      #   # The `always_true` style enforces that the frozen string literal
+      #   # comment is set to `true`. This is a stricter option than `always`
+      #   # and forces projects to use frozen string literals.
+      #   # bad
+      #   # frozen_string_literal: false
+      #
+      #   module Baz
+      #     # ...
+      #   end
+      #
+      #   # bad
+      #   module Baz
+      #     # ...
+      #   end
+      #
+      #   # good
+      #   # frozen_string_literal: true
+      #
+      #   module Bar
+      #     # ...
+      #   end
       class FrozenStringLiteralComment < Cop
         include ConfigurableEnforcedStyle
         include FrozenStringLiteral
         include RangeHelp
 
-        MSG = 'Missing magic comment `# frozen_string_literal: true`.'
+        MSG_MISSING_TRUE = 'Missing magic comment `# frozen_string_literal: '\
+                           'true`.'
+        MSG_MISSING = 'Missing magic "frozen_string_literal" comment.'
         MSG_UNNECESSARY = 'Unnecessary frozen string literal comment.'
+        MSG_DISABLED = 'Frozen string literal comment must be set to `true`.'
         SHEBANG = '#!'
 
         def investigate(processed_source)
           return if processed_source.tokens.empty?
 
-          if frozen_string_literal_comment_exists?
-            check_for_no_comment(processed_source)
+          case style
+          when :never
+            ensure_no_comment(processed_source)
+          when :always_true
+            ensure_enabled_comment(processed_source)
           else
-            check_for_comment(processed_source)
+            ensure_comment(processed_source)
           end
         end
 
         def autocorrect(node)
           lambda do |corrector|
-            if style == :never
+            case style
+            when :never
               remove_comment(corrector, node)
+            when :always_true
+              if frozen_string_literal_specified?
+                enable_comment(corrector)
+              else
+                insert_comment(corrector)
+              end
             else
               insert_comment(corrector)
             end
@@ -82,12 +118,27 @@ def autocorrect(node)
 
         private
 
-        def check_for_no_comment(processed_source)
-          unnecessary_comment_offense(processed_source) if style == :never
+        def ensure_no_comment(processed_source)
+          return unless frozen_string_literal_comment_exists?
+
+          unnecessary_comment_offense(processed_source)
         end
 
-        def check_for_comment(processed_source)
-          offense(processed_source) unless style == :never
+        def ensure_comment(processed_source)
+          return if frozen_string_literal_comment_exists?
+
+          missing_offense(processed_source)
+        end
+
+        def ensure_enabled_comment(processed_source)
+          if frozen_string_literal_specified?
+            return if frozen_string_literals_enabled?
+
+            # The comment exists, but is not enabled.
+            disabled_offense(processed_source)
+          else # The comment doesn't exist at all.
+            missing_true_offense(processed_source)
+          end
         end
 
         def last_special_comment(processed_source)
@@ -111,11 +162,22 @@ def frozen_string_literal_comment(processed_source)
           end
         end
 
-        def offense(processed_source)
+        def missing_offense(processed_source)
+          last_special_comment = last_special_comment(processed_source)
+          range = source_range(processed_source.buffer, 0, 0)
+
+          add_offense(last_special_comment,
+                      location: range,
+                      message: MSG_MISSING)
+        end
+
+        def missing_true_offense(processed_source)
           last_special_comment = last_special_comment(processed_source)
           range = source_range(processed_source.buffer, 0, 0)
 
-          add_offense(last_special_comment, location: range)
+          add_offense(last_special_comment,
+                      location: range,
+                      message: MSG_MISSING_TRUE)
         end
 
         def unnecessary_comment_offense(processed_source)
@@ -127,11 +189,27 @@ def unnecessary_comment_offense(processed_source)
                       message: MSG_UNNECESSARY)
         end
 
+        def disabled_offense(processed_source)
+          frozen_string_literal_comment =
+            frozen_string_literal_comment(processed_source)
+
+          add_offense(frozen_string_literal_comment,
+                      location: frozen_string_literal_comment.pos,
+                      message: MSG_DISABLED)
+        end
+
         def remove_comment(corrector, node)
           corrector.remove(range_with_surrounding_space(range: node.pos,
                                                         side: :right))
         end
 
+        def enable_comment(corrector)
+          comment = frozen_string_literal_comment(processed_source)
+
+          corrector.replace(line_range(comment.line),
+                            FROZEN_STRING_LITERAL_ENABLED)
+        end
+
         def insert_comment(corrector)
           comment = last_special_comment(processed_source)
 

manual/cops_style.md

@@ -2328,12 +2328,37 @@ module Baz
   # ...
 end
 ```
+#### EnforcedStyle: always_true
+
+```ruby
+# The `always_true` style enforces that the frozen string literal
+# comment is set to `true`. This is a stricter option than `always`
+# and forces projects to use frozen string literals.
+# bad
+# frozen_string_literal: false
+
+module Baz
+  # ...
+end
+
+# bad
+module Baz
+  # ...
+end
+
+# good
+# frozen_string_literal: true
+
+module Bar
+  # ...
+end
+```
 
 ### Configurable attributes
 
 Name | Default value | Configurable values
 --- | --- | ---
-EnforcedStyle | `always` | `always`, `never`
+EnforcedStyle | `always` | `always`, `always_true`, `never`
 
 ## Style/GlobalVars
 

spec/fixtures/html_formatter/expected.html

@@ -418,7 +418,7 @@ <h1 class="title">RuboCop Inspection Report</h1>
             <div class="meta">
               <span class="location">Line #1</span> –
               <span class="severity convention">convention:</span>
-              <span class="message">Style/FrozenStringLiteralComment: Missing magic comment <code># frozen_string_literal: true</code>.</span>
+              <span class="message">Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.</span>
             </div>
 
             <pre><code><span class="highlight convention">c</span>lass ApplicationController &lt; ActionController::Base</code></pre>
@@ -461,7 +461,7 @@ <h1 class="title">RuboCop Inspection Report</h1>
             <div class="meta">
               <span class="location">Line #1</span> –
               <span class="severity convention">convention:</span>
-              <span class="message">Style/FrozenStringLiteralComment: Missing magic comment <code># frozen_string_literal: true</code>.</span>
+              <span class="message">Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.</span>
             </div>
 
             <pre><code><span class="highlight convention">c</span>lass BooksController &lt; ApplicationController</code></pre>
@@ -625,7 +625,7 @@ <h1 class="title">RuboCop Inspection Report</h1>
             <div class="meta">
               <span class="location">Line #1</span> –
               <span class="severity convention">convention:</span>
-              <span class="message">Style/FrozenStringLiteralComment: Missing magic comment <code># frozen_string_literal: true</code>.</span>
+              <span class="message">Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.</span>
             </div>
 
             <pre><code><span class="highlight convention">c</span>lass Book &lt; ActiveRecord::Base</code></pre>

spec/rubocop/cli/cli_auto_gen_config_spec.rb

@@ -178,7 +178,7 @@ def f
               # Offense count: 1
               # Cop supports --auto-correct.
               # Configuration parameters: EnforcedStyle.
-              # SupportedStyles: always, never
+              # SupportedStyles: always, always_true, never
               Style/FrozenStringLiteralComment:
                 Exclude:
                   - 'example.rb'
@@ -226,7 +226,7 @@ def f
               # Offense count: 1
               # Cop supports --auto-correct.
               # Configuration parameters: EnforcedStyle.
-              # SupportedStyles: always, never
+              # SupportedStyles: always, always_true, never
               Style/FrozenStringLiteralComment:
                 Exclude:
                   - 'example.rb'
@@ -276,7 +276,7 @@ def f
               # Offense count: 1
               # Cop supports --auto-correct.
               # Configuration parameters: EnforcedStyle.
-              # SupportedStyles: always, never
+              # SupportedStyles: always, always_true, never
               Style/FrozenStringLiteralComment:
                 Exclude:
                   - 'example.rb'
@@ -369,7 +369,7 @@ def f
                 '# Offense count: 1',
                 '# Cop supports --auto-correct.',
                 '# Configuration parameters: EnforcedStyle.',
-                '# SupportedStyles: always, never',
+                '# SupportedStyles: always, always_true, never',
                 'Style/FrozenStringLiteralComment:',
                 '  Exclude:',
                 "    - 'example1.rb'",
@@ -411,7 +411,7 @@ def f
           # Offense count: 1
           # Cop supports --auto-correct.
           # Configuration parameters: EnforcedStyle.
-          # SupportedStyles: always, never
+          # SupportedStyles: always, always_true, never
           Style/FrozenStringLiteralComment:
             Exclude:
               - 'example1.rb'
@@ -459,7 +459,7 @@ def f
           # Offense count: 1
           # Cop supports --auto-correct.
           # Configuration parameters: EnforcedStyle.
-          # SupportedStyles: always, never
+          # SupportedStyles: always, always_true, never
           Style/FrozenStringLiteralComment:
             Exclude:
               - 'example1.rb'
@@ -1006,7 +1006,7 @@ def function(arg1, arg2, arg3, arg4, arg5, arg6, arg7)
             # Offense count: 3
             # Cop supports --auto-correct.
             # Configuration parameters: EnforcedStyle.
-            # SupportedStyles: always, never
+            # SupportedStyles: always, always_true, never
             Style/FrozenStringLiteralComment:
               Enabled: false
 
@@ -1027,7 +1027,7 @@ def function(arg1, arg2, arg3, arg4, arg5, arg6, arg7)
             # Offense count: 4
             # Cop supports --auto-correct.
             # Configuration parameters: EnforcedStyle.
-            # SupportedStyles: always, never
+            # SupportedStyles: always, always_true, never
             Style/FrozenStringLiteralComment:
               Exclude:
                 - 'example1.rb'

spec/rubocop/cli/cli_autocorrect_spec.rb

@@ -765,7 +765,7 @@ def func
     expect(cli.run(%w[--auto-correct --format simple])).to eq(1)
     expect($stdout.string).to eq(<<~RESULT)
       == example.rb ==
-      C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+      C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
       C:  2:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
       C:  3:  1: Style/Documentation: Missing top-level class documentation comment.
       W:  4:  3: [Corrected] Lint/RedundantCopDisableDirective: Unnecessary disabling of Metrics/MethodLength.

spec/rubocop/cli/cli_disable_uncorrectable_spec.rb

@@ -16,7 +16,7 @@
       expect($stderr.string).to eq('')
       expect($stdout.string).to eq(<<~OUTPUT)
         == example.rb ==
-        C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+        C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
         C:  1:  7: [Corrected] Layout/SpaceAroundOperators: Surrounding space missing for operator ==.
         C:  2:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
 
@@ -40,7 +40,7 @@ def is_example
         expect($stderr.string).to eq('')
         expect($stdout.string).to eq(<<~OUTPUT)
           == example.rb ==
-          C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+          C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
           C:  1:  5: [Todo] Naming/PredicateName: Rename is_example to example?.
           C:  2:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
 
@@ -68,7 +68,7 @@ def is_example # rubocop:todo Naming/PredicateName
           expect($stderr.string).to eq('')
           expect($stdout.string).to eq(<<~OUTPUT)
             == example.rb ==
-            C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+            C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
             C:  1:  4: [Todo] Style/IpAddresses: Do not hardcode IP addresses.
             C:  1: 15: [Todo] Style/IpAddresses: Do not hardcode IP addresses.
             C:  2:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
@@ -111,7 +111,7 @@ def choose_move(who_to_move)
           expect($stderr.string).to eq('')
           expect($stdout.string).to eq(<<~OUTPUT)
             == example.rb ==
-            C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+            C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
             C:  2:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
             C:  3:  3: [Todo] Metrics/AbcSize: Assignment Branch Condition size for choose_move is too high. [<8, 12, 6> 15.62/15]
             C:  3:  3: [Todo] Metrics/CyclomaticComplexity: Cyclomatic complexity for choose_move is too high. [7/6]
@@ -170,7 +170,7 @@ def long_method_name(_taking, _a_few, _parameters, _resulting_in_a_long_line)
         expect($stdout.string).to eq(<<~OUTPUT)
           == example.rb ==
           C:  1:  1: [Todo] Metrics/MethodLength: Method has too many lines. [2/1]
-          C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.
+          C:  1:  1: [Corrected] Style/FrozenStringLiteralComment: Missing magic "frozen_string_literal" comment.
           C:  3:  1: [Corrected] Layout/EmptyLineAfterMagicComment: Add an empty line after magic comments.
 
           1 file inspected, 3 offenses detected, 3 offenses corrected