[Fix #10134] Update Style/MutableConstant to not consider multiline uninterpolated strings as unfrozen in ruby 3.0

changelog/fix_update_stylemutableconstant_to_not.md

@@ -0,0 +1 @@
+* [#10134](https://github.com/rubocop/rubocop/issues/10134): Update `Style/MutableConstant` to not consider multiline uninterpolated strings as unfrozen in ruby 3.0. ([@dvandersluis][])

lib/rubocop/cop/mixin/frozen_string_literal.rb

@@ -20,14 +20,18 @@ def frozen_string_literal_comment_exists?
 
       def frozen_string_literal?(node)
         frozen_string = if target_ruby_version >= 3.0
-                          node.str_type? || frozen_heredoc?(node)
+                          uninterpolated_string?(node) || frozen_heredoc?(node)
                         else
                           FROZEN_STRING_LITERAL_TYPES_RUBY27.include?(node.type)
                         end
 
         frozen_string && frozen_string_literals_enabled?
       end
 
+      def uninterpolated_string?(node)
+        node.str_type? || (node.dstr_type? && node.each_descendant(:begin).none?)
+      end
+
       def frozen_heredoc?(node)
         return false unless node.dstr_type? && node.heredoc?
 

lib/rubocop/cop/style/mutable_constant.rb

@@ -21,8 +21,9 @@ module Style
       #
       # NOTE: Regexp and Range literals are frozen objects since Ruby 3.0.
       #
-      # NOTE: From Ruby 3.0, this cop allows explicit freezing of interpolated
-      # string literals when `# frozen-string-literal: true` is used.
+      # NOTE: From Ruby 3.0, interpolated strings are not frozen when
+      # `# frozen-string-literal: true` is used, so this cop enforces explicit
+      # freezing for such strings.
       #
       # NOTE: From Ruby 3.0, this cop allows explicit freezing of constants when
       # the `shareable_constant_value` directive is used.

spec/rubocop/cop/style/mutable_constant_spec.rb

@@ -132,6 +132,25 @@
             HERE
           RUBY
         end
+
+        it 'does not register an offense when using a multiline string' do
+          expect_no_offenses(<<~RUBY)
+            # frozen_string_literal: true
+
+            CONST = 'foo' \
+                    'bar'
+          RUBY
+        end
+
+        it 'registers an offense when using a multiline string with interpolation' do
+          expect_offense(<<~'RUBY')
+            # frozen_string_literal: true
+
+            CONST = "#{foo}" \
+                    ^^^^^^^^^^ Freeze mutable objects assigned to constants.
+                    'bar'
+          RUBY
+        end
       end
 
       context 'when the frozen string literal comment is false' do
@@ -166,6 +185,15 @@
             HERE
           RUBY
         end
+
+        it 'does not register an offense when using a multiline string' do
+          expect_no_offenses(<<~RUBY)
+            # frozen_string_literal: true
+
+            CONST = 'foo' \
+                    'bar'
+          RUBY
+        end
       end
 
       context 'when the frozen string literal comment is false' do