Allow safety information to be added to cop descriptions.

Register a `@safety` custom YARD tag, and uses it to create a new section to the documentation about cop safety. Also updates the `new_cop` template to add the `@safety` tag section.

.yardopts

@@ -1,2 +1,3 @@
 --markup markdown
 --hide-void-return
+--tag safety:"Cop Safety Information"

lib/rubocop/cop/generator.rb

@@ -24,6 +24,11 @@ module %<department>s
               # `SupportedStyle` and unique configuration, there needs to be examples.
               # Examples must have valid Ruby syntax. Do not use upticks.
               #
+              # @safety
+              #   Delete this section if the cop is not unsafe (`Safe: false` or
+              #   `SafeAutoCorrect: false`), or use it to explain how the cop is
+              #   unsafe.
+              #
               # @example EnforcedStyle: bar (default)
               #   # Description of the `bar` style.
               #

lib/rubocop/cops_documentation_generator.rb

@@ -33,11 +33,12 @@ def cops_of_department(department)
     cops.with_department(department).sort!
   end
 
-  def cops_body(cop, description, examples_objects, pars)
+  def cops_body(cop, description, examples_objects, safety_objects, pars) # rubocop:disable Metrics/AbcSize
     content = h2(cop.cop_name)
     content << required_ruby_version(cop)
     content << properties(cop)
     content << "#{description}\n"
+    content << safety_object(safety_objects) if safety_objects.any? { |s| !s.text.blank? }
     content << examples(examples_objects) if examples_objects.count.positive?
     content << configurations(pars)
     content << references(cop)
@@ -52,6 +53,16 @@ def examples(examples_object)
     end
   end
 
+  def safety_object(safety_object_objects)
+    safety_object_objects.each_with_object(h3('Safety').dup) do |safety_object, content|
+      next if safety_object.text.blank?
+
+      content << "\n" unless content.end_with?("\n\n")
+      content << safety_object.text
+      content << "\n"
+    end
+  end
+
   def required_ruby_version(cop)
     return '' unless cop.respond_to?(:required_minimum_ruby_version)
 
@@ -61,8 +72,8 @@ def required_ruby_version(cop)
   # rubocop:disable Metrics/MethodLength
   def properties(cop)
     header = [
-      'Enabled by default', 'Safe', 'Supports autocorrection', 'VersionAdded',
-      'VersionChanged'
+      'Enabled by default', 'Safe', 'Supports autocorrection', 'Version Added',
+      'Version Changed'
     ]
     autocorrect = if cop.support_autocorrect?
                     "Yes#{' (Unsafe)' unless cop.new(config).safe_autocorrect?}"
@@ -217,12 +228,13 @@ def print_cop_with_doc(cop)
     ]
     pars = cop_config.reject { |k| non_display_keys.include? k }
     description = 'No documentation'
-    examples_object = []
+    examples_object = safety_object = []
     cop_code(cop) do |code_object|
       description = code_object.docstring unless code_object.docstring.blank?
       examples_object = code_object.tags('example')
+      safety_object = code_object.tags('safety')
     end
-    cops_body(cop, description, examples_object, pars)
+    cops_body(cop, description, examples_object, safety_object, pars)
   end
 
   def cop_code(cop)

spec/rubocop/cop/generator_spec.rb

@@ -25,6 +25,11 @@ module Style
               # `SupportedStyle` and unique configuration, there needs to be examples.
               # Examples must have valid Ruby syntax. Do not use upticks.
               #
+              # @safety
+              #   Delete this section if the cop is not unsafe (`Safe: false` or
+              #   `SafeAutoCorrect: false`), or use it to explain how the cop is
+              #   unsafe.
+              #
               # @example EnforcedStyle: bar (default)
               #   # Description of the `bar` style.
               #