Deprecate public methods for removed collection size feature

app/models/concerns/hyrax/collection_behavior.rb

@@ -111,6 +111,17 @@ def collection_type_gid_document_field_name
       end
     end
 
+    # @deprecated to be removed in 4.0.0; this feature was replaced with a
+    #   hard-coded null implementation
+    # @return [Fixnum] 0
+    def bytes
+      Deprecation.warn('#bytes has been deprecated for removal in Hyrax 4.0.0; ' \
+                       'The implementation of the indexed Collection size ' \
+                       'feature is extremely inefficient, so it has been removed. ' \
+                       'This method now returns a hard-coded `0` for compatibility.')
+      0
+    end
+
     # @api public
     # Retrieve the permission template for this collection.
     # @return [Hyrax::PermissionTemplate]

app/presenters/hyrax/collection_presenter.rb

@@ -41,23 +41,40 @@ def collection_type
     # Terms is the list of fields displayed by
     # app/views/collections/_show_descriptions.html.erb
     def self.terms
-      [:total_items, :resource_type, :creator, :contributor, :keyword, :license, :publisher, :date_created, :subject,
+      [:total_items, :size, :resource_type, :creator, :contributor, :keyword, :license, :publisher, :date_created, :subject,
        :language, :identifier, :based_near, :related_url]
     end
 
     def terms_with_values
       self.class.terms.select { |t| self[t].present? }
     end
 
+    ##
+    # @param [Symbol] key
+    # @return [Object]
     def [](key)
       case key
+      when :size
+        size
       when :total_items
         total_items
       else
         solr_document.send key
       end
     end
 
+    # @deprecated to be removed in 4.0.0; this feature was replaced with a
+    #   hard-coded null implementation
+    # @return [String] 'unknown'
+    def size
+      Deprecation.warn('#size has been deprecated for removal in Hyrax 4.0.0; ' \
+                       'The implementation of the indexed Collection size ' \
+                       'feature is extremely inefficient, so it has been removed. ' \
+                       'This method now returns a hard-coded `"unknown"` for ' \
+                       'compatibility.')
+      'unknown'
+    end
+
     def total_items
       ActiveFedora::Base.where("member_of_collection_ids_ssim:#{id}").count
     end

spec/models/collection_spec.rb

@@ -5,6 +5,13 @@
     expect(collection.read_groups).to eq ['public']
   end
 
+  describe '#bytes' do
+    it 'returns a hard-coded integer and issues a deprecation warning' do
+      expect(Deprecation).to receive(:warn).once
+      expect(collection.bytes).to eq(0)
+    end
+  end
+
   describe "#validates_with" do
     before { collection.title = nil }
     it "ensures the collection has a title" do

spec/presenters/hyrax/collection_presenter_spec.rb

@@ -3,7 +3,7 @@
     subject { described_class.terms }
 
     it do
-      is_expected.to eq [:total_items, :resource_type, :creator,
+      is_expected.to eq [:total_items, :size, :resource_type, :creator,
                          :contributor, :keyword, :license, :publisher,
                          :date_created, :subject, :language, :identifier,
                          :based_near, :related_url]
@@ -78,6 +78,7 @@
 
     it do
       is_expected.to eq [:total_items,
+                         :size,
                          :resource_type,
                          :keyword,
                          :date_created,
@@ -122,6 +123,13 @@
     it { is_expected.to eq ['adc12v'] }
   end
 
+  describe '#size' do
+    it 'returns a hard-coded string and issues a deprecation warning' do
+      expect(Deprecation).to receive(:warn).once
+      expect(presenter.size).to eq('unknown')
+    end
+  end
+
   describe "#total_items", :clean_repo do
     subject { presenter.total_items }