Create FormulaCop base class to reuse helper functions in custom cops

Library/.rubocop.yml

@@ -8,7 +8,17 @@ AllCops:
 
 require: ./Homebrew/rubocops.rb
 
+Homebrew/FormulaCop:
+  Enabled: false
+
 Homebrew/CorrectBottleBlock:
+  Include:
+    - '**/Taps/homebrew/**/*.rb'
+  Enabled: true
+
+Homebrew/FormulaDesc:
+  Include:
+    - '**/Taps/homebrew/**/*.rb'
   Enabled: true
 
 Metrics/AbcSize:

Library/Homebrew/rubocops/bottle_block_cop.rb

@@ -1,20 +1,31 @@
+require_relative "./extend/formula_cop"
+
 module RuboCop
   module Cop
     module Homebrew
-      class CorrectBottleBlock < Cop
+      # This cop audits `bottle` block in Formulae
+      #
+      # - `rebuild` should be used instead of `revision` in `bottle` block
+
+      class CorrectBottleBlock < FormulaCop
         MSG = "Use rebuild instead of revision in bottle block".freeze
 
-        def on_block(node)
-          return if block_length(node).zero?
-          method, _args, body = *node
-          _keyword, method_name = *method
-
-          return unless method_name == :bottle
-          check_revision?(body)
+        def audit_formula(_node, _class_node, _parent_class_node, formula_class_body_node)
+          check(formula_class_body_node)
         end
 
         private
 
+        def check(formula_class_body_node)
+          formula_class_body_node.each_child_node(:block) do |block_node|
+            next if block_length(block_node).zero?
+            method, _args, block_body = *block_node
+            _keyword, method_name = *method
+            next unless method_name == :bottle
+            check_revision?(block_body)
+          end
+        end
+
         def autocorrect(node)
           lambda do |corrector|
             correction = node.source.sub("revision", "rebuild")

Library/Homebrew/rubocops/extend/formula_cop.rb

@@ -0,0 +1,22 @@
+module RuboCop
+  module Cop
+    module Homebrew
+      class FormulaCop < Cop
+        @registry = Cop.registry
+
+        def on_class(node)
+          # This method is called by RuboCop and is the main entry point
+          class_node, parent_class_node, body = *node
+          return unless a_formula_class?(parent_class_node)
+          audit_formula(node, class_node, parent_class_node, body)
+        end
+
+        private
+
+        def a_formula_class?(parent_class_node)
+          parent_class_node && parent_class_node.const_name == "Formula"
+        end
+      end
+    end
+  end
+end

Library/Homebrew/rubocops/formula_desc_cop.rb

@@ -1,12 +1,20 @@
+require_relative "./extend/formula_cop"
+require_relative "../extend/string"
+
 module RuboCop
   module Cop
     module Homebrew
-      class FormulaDesc < Cop
-        def on_class(node)
-          class_node, parent_class_node, body = *node
-          formula_name = class_node.const_name
-          return unless parent_class_node && parent_class_node.const_name == "Formula" && body
-          check(node, body, formula_name)
+      # This cop audits `desc` in Formulae
+      #
+      # - Checks for existence of `desc`
+      # - Checks if size of `desc` > 80
+      # - Checks if `desc` begins with an article
+      # - Checks for correct usage of `command-line` in `desc`
+      # - Checks if `desc` contains the formula name
+
+      class FormulaDesc < FormulaCop
+        def audit_formula(node, class_node, _parent_class_node, body)
+          check(node, body, class_node.const_name)
         end
 
         private
@@ -14,7 +22,7 @@ module RuboCop
         def check(node, body, formula_name)
           body.each_child_node(:send) do |call_node|
             _receiver, call_name, args = *call_node
-            next unless call_name == :desc && !args.children[0].empty?
+            next if call_name != :desc || args.children[0].empty?
             description = args.children[0]
 
             source_buffer = call_node.source_range.source_buffer
@@ -27,27 +35,29 @@ module RuboCop
               column = desc_begin_pos - line_begin_pos
               length = call_node.children[2].source_range.size
               sourcerange = source_range(source_buffer, line_number, column, length)
-              message = <<-EOS.strip_indent
-                        Description is too long. \"name: desc\" should be less than 80 characters.
+              message = <<-EOS.undent
+                Description is too long. "name: desc" should be less than 80 characters.
                 Length is calculated as #{formula_name} + desc. (currently #{linelength})
               EOS
               add_offense(call_node, sourcerange, message)
             end
 
-            match_object = description.match(/([Cc]ommand ?line)/)
+            match_object = description.match(/(command ?line)/i)
             if match_object
               column = desc_begin_pos+match_object.begin(0)-line_begin_pos+1
               length = match_object.to_s.length
               sourcerange = source_range(source_buffer, line_number, column, length)
-              add_offense(call_node, sourcerange, "Description should use \"command-line\" instead of \"#{match_object}\"")
+              message = "Description should use \"command-line\" instead of \"#{match_object}\""
+              add_offense(call_node, sourcerange, message)
             end
 
-            match_object = description.match(/^([Aa]n?)\s/)
+            match_object = description.match(/^(an?)\s/i)
             if match_object
               column = desc_begin_pos+match_object.begin(0)-line_begin_pos+1
               length = match_object.to_s.length
               sourcerange = source_range(source_buffer, line_number, column, length)
-              add_offense(call_node, sourcerange, "Description shouldn't start with an indefinite article (#{match_object})")
+              message = "Description shouldn't start with an indefinite article (#{match_object})"
+              add_offense(call_node, sourcerange, message)
             end
 
             match_object = description.match(/^#{formula_name}/i)
@@ -55,9 +65,10 @@ module RuboCop
               column = desc_begin_pos+match_object.begin(0)-line_begin_pos+1
               length = match_object.to_s.length
               sourcerange = source_range(source_buffer, line_number, column, length)
-              add_offense(call_node, sourcerange, "Description shouldn't include the formula name")
+              message = "Description shouldn't include the formula name"
+              add_offense(call_node, sourcerange, message)
             end
-            return
+            return nil
           end
           add_offense(node, node.source_range, "Formula should have a desc (Description).")
         end