💄 Add custom cop for include Hyrax::ArResource

This commit will add a custom cop to RuboCop that will check for
`include Hyrax::ArResrouce` or `include ArRdResource` in the codebase.
The `ArResource` module is just for development ease of use and should
not be used within the codebase.

The custom cop leaves an example for additional custom cops that can be
used in the future and where to test them.  The key is to make sure the
`.rubocop.yml` file is updated to include the new cop.  The pattern for
it is adding something like Hyrax::RuboCop::CustomCops::SomeCop would be

```yaml
Hyrax/SomeCop:
  Enabled: true
```

From what I gather it is taking the top most namespace and then the
class name.

.rubocop.yml

@@ -1,3 +1,5 @@
+require: ./lib/hyrax/rubocop/custom_cops.rb
+
 inherit_from:
   - .rubocop_fixme.yml
 
@@ -125,3 +127,6 @@ RSpec/NestedGroups:
 
 RSpec/LeadingSubject:
   Enabled: false
+
+Hyrax/ArResource:
+  Enabled: true

lib/hyrax/engine.rb

@@ -34,6 +34,7 @@ class Engine < ::Rails::Engine
     require 'hyrax/transactions'
     require 'hyrax/errors'
     require 'hyrax/valkyrie_simple_path_generator'
+    require 'hyrax/rubocop/custom_cops'
 
     # Force these models to be added to Legato's registry in development mode
     config.eager_load_paths += %W[

lib/hyrax/rubocop/custom_cops.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require 'rubocop'
+
+module Hyrax
+  module RuboCop
+    module CustomCops
+      # This custom cop checks for mixins of Hyrax::ArResource
+      class ArResource < ::RuboCop::Cop::Cop
+        MSG = 'Do not `include Hyrax::ArResource`.'
+
+        # checks for `include Hyrax::ArResource`
+        def_node_search :includes_hyrax_ar_resource?, <<-PATTERN
+          (send nil? {:include :extend} (const (const nil? :Hyrax) :ArResource))
+        PATTERN
+
+        # checks for `include ArResource`
+        def_node_search :includes_ar_resource?, <<-PATTERN
+          (send nil? {:include :extend} (const nil? :ArResource))
+        PATTERN
+
+        def on_send(send_node)
+          add_offense(send_node, message: MSG) if includes_hyrax_ar_resource?(send_node) || includes_ar_resource?(send_node)
+        end
+      end
+
+      # class AdditionalCustomCops < ::RuboCop::Cop::Cop; end
+    end
+  end
+end

spec/lib/hyrax/rubocop/custom_cops_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+RSpec.describe Hyrax::RuboCop::CustomCops::ArResource do
+  subject(:cop) { described_class.new }
+
+  it 'is not allowed to include Hyrax::ArResource' do
+    expect_offense(<<~RUBY)
+      include Hyrax::ArResource
+      ^^^^^^^^^^^^^^^^^^^^^^^^^ Do not `include Hyrax::ArResource`.
+    RUBY
+  end
+
+  it 'is not allowed to include ArResource' do
+    expect_offense(<<~RUBY)
+      include ArResource
+      ^^^^^^^^^^^^^^^^^^ Do not `include Hyrax::ArResource`.
+    RUBY
+  end
+end
+
+# RSpec.describe Hyrax::RuboCop::CustomCops::AdditionalCustomCops  do; end

spec/spec_helper.rb

@@ -50,6 +50,9 @@ def ci_build?
 require 'hyrax/specs/clamav'
 require 'hyrax/specs/engine_routes'
 
+require 'rubocop'
+require 'rubocop/rspec/support'
+
 # ensure Hyrax::Schema gets loaded is resolvable for `support/` models
 Hyrax::Schema # rubocop:disable Lint/Void
 
@@ -364,4 +367,6 @@ def clean_active_fedora_repository
       .to receive(:storage_adapter)
       .and_return(Valkyrie::StorageAdapter.find(adapter_name))
   end
+
+  config.include RuboCop::RSpec::ExpectOffense
 end