audit: Port audit_conflicts method to rubocop and add tests

Library/.rubocop.yml

@@ -18,6 +18,9 @@ FormulaAudit/Checksum:
 FormulaAudit/ChecksumCase:
   Enabled: true
 
+FormulaAudit/Conflicts:
+  Enabled: true
+
 FormulaAuditStrict/BottleBlock:
   Enabled: true
 

Library/Homebrew/dev-cmd/audit.rb

@@ -519,15 +519,6 @@ class FormulaAuditor
         problem "Ambiguous conflicting formula #{c.name.inspect}."
       end
     end
-
-    versioned_conflicts_whitelist = %w[node@ bash-completion@].freeze
-
-    return unless formula.conflicts.any? && formula.versioned_formula?
-    return if formula.name.start_with?(*versioned_conflicts_whitelist)
-    problem <<-EOS
-      Versioned formulae should not use `conflicts_with`.
-      Use `keg_only :versioned_formula` instead.
-    EOS
   end
 
   def audit_keg_only_style

Library/Homebrew/rubocops.rb

@@ -7,3 +7,4 @@ require_relative "./rubocops/text_cop"
 require_relative "./rubocops/caveats_cop"
 require_relative "./rubocops/checksum_cop"
 require_relative "./rubocops/legacy_patches_cop"
+require_relative "./rubocops/conflicts_cop"

Library/Homebrew/rubocops/conflicts_cop.rb

@@ -0,0 +1,27 @@
+require_relative "./extend/formula_cop"
+require_relative "../extend/string"
+
+module RuboCop
+  module Cop
+    module FormulaAudit
+      # This cop audits versioned Formulae for `conflicts_with`
+      class Conflicts < FormulaCop
+        MSG = <<-EOS.undent
+          Versioned formulae should not use `conflicts_with`.
+          Use `keg_only :versioned_formula` instead.
+        EOS
+
+        WHITELIST = %w[
+          node@
+          bash-completion@
+        ].freeze
+
+        def audit_formula(_node, _class_node, _parent_class_node, body)
+          return unless versioned_formula?
+          problem MSG if !formula_file_name.start_with?(*WHITELIST) &&
+                         method_called_ever?(body, :conflicts_with)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/rubocops/extend/formula_cop.rb

@@ -344,6 +344,16 @@ module RuboCop
         end
       end
 
+      # Returns true if the formula is versioned
+      def versioned_formula?
+        formula_file_name.include?("@") || @formula_name.match(/AT\d+/)
+      end
+
+      # Returns filename of the formula without the extension
+      def formula_file_name
+        File.basename(processed_source.buffer.name, ".rb")
+      end
+
       # Returns printable component name
       def format_component(component_node)
         return component_node.method_name if component_node.send_type? || component_node.block_type?

Library/Homebrew/test/rubocops/conflicts_cop_spec.rb

@@ -0,0 +1,47 @@
+require "rubocop"
+require "rubocop/rspec/support"
+require_relative "../../extend/string"
+require_relative "../../rubocops/conflicts_cop"
+
+describe RuboCop::Cop::FormulaAudit::Conflicts do
+  subject(:cop) { described_class.new }
+
+  context "When auditing formula for conflicts with" do
+    it "multiple conflicts_with" do
+      source = <<-EOS.undent
+        class FooAT20 < Formula
+          url 'http://example.com/foo-2.0.tgz'
+          conflicts_with "mysql", "mariadb", "percona-server",
+                           :because => "both install plugins"
+        end
+      EOS
+
+      msg = <<-EOS.undent
+            Versioned formulae should not use `conflicts_with`.
+            Use `keg_only :versioned_formula` instead.
+      EOS
+      expected_offenses = [{  message: msg,
+                              severity: :convention,
+                              line: 3,
+                              column: 2,
+                              source: source }]
+
+      inspect_source(cop, source)
+
+      expected_offenses.zip(cop.offenses).each do |expected, actual|
+        expect_offense(expected, actual)
+      end
+    end
+
+    it "no conflicts_with" do
+      source = <<-EOS.undent
+        class FooAT20 < Formula
+          url 'http://example.com/foo-2.0.tgz'
+          desc 'Bar'
+        end
+      EOS
+      inspect_source(cop, source)
+      expect(cop.offenses).to eq([])
+    end
+  end
+end