🐛 Favor overriding CollectionsController

This commit will allow us to override the CollectionsController instead
of the Blacklight::ConfigurationHelperBehavior.  A bug was noticed when
switching the sort fields that the field selected wouldn't stick in the
UI even though the fields were actually sorting correctly.  Overriding
the CollectionsController will be a better pattern since we override the
WorksController in the same way.  The reason why we didn't do that in
the first place was because it caused the show page to have the same
sort fields as the index page.  In this commit, we are also modifying
the show page to reconfigure the sort fields to address the issue.

Ref:
  - #748

app/controllers/hyrax/dashboard/collections_controller.rb

@@ -73,6 +73,8 @@ def new
       end
 
       def show
+        configure_show_sort_fields
+
         # unused assignment to be removed in 4.0.0
         @banner_file = presenter.banner_file if collection_type.brandable?
 
@@ -732,6 +734,13 @@ def process_file_location(f)
         end
       end
       ## END OVERRIDE
+
+      def configure_show_sort_fields
+        # In the CollectionsControllerDecorator, we clear the sort fields and add our own to have
+        # the ability to sort the index with custom fields. However, this also affects the show page.
+        # Here we set the sort fields back to the defaults for the show page.
+        blacklight_config.sort_fields = CatalogController.blacklight_config.sort_fields
+      end
     end
   end
 end

app/controllers/hyrax/my/collections_controller_decorator.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module Hyrax
+  module My
+    module CollectionsControllerDecorator
+      def configure_facets
+        configure_blacklight do |config|
+          # clear facets copied from the CatalogController
+          config.sort_fields.clear
+          # Collections don't seem to have a date_uploaded_dtsi nor date_modified_dtsi
+          # we can at least use the system_modified_dtsi instead of date_modified_dtsi
+          # but we will omit date_uploaded_dtsi
+          config.add_sort_field "system_modified_dtsi desc", label: "date modified \u25BC"
+          config.add_sort_field "system_modified_dtsi asc", label: "date modified \u25B2"
+          config.add_sort_field "system_create_dtsi desc", label: "date created \u25BC"
+          config.add_sort_field "system_create_dtsi asc", label: "date created \u25B2"
+          config.add_sort_field "depositor_ssi asc, title_ssi asc", label: "depositor (A-Z)"
+          config.add_sort_field "depositor_ssi desc, title_ssi desc", label: "depositor (Z-A)"
+          config.add_sort_field "creator_ssi asc, title_ssi asc", label: "creator (A-Z)"
+          config.add_sort_field "creator_ssi desc, title_ssi desc", label: "creator (Z-A)"
+        end
+      end
+    end
+  end
+end
+
+Hyrax::My::CollectionsController.singleton_class.send(:prepend, Hyrax::My::CollectionsControllerDecorator)
+Hyrax::My::CollectionsController.configure_facets

app/controllers/hyrax/my/works_controller_decorator.rb

@@ -7,10 +7,8 @@ module My
     module WorksControllerDecorator
       def configure_facets
         configure_blacklight do |config|
-          config.sort_fields.each_key do |key|
-            config.sort_fields.delete(key)
-          end
-
+          # clear facets copied from the CatalogController
+          config.sort_fields.clear
           config.add_sort_field "date_uploaded_dtsi desc", label: "date uploaded \u25BC"
           config.add_sort_field "date_uploaded_dtsi asc", label: "date uploaded \u25B2"
           config.add_sort_field "date_modified_dtsi desc", label: "date modified \u25BC"

spec/controllers/hyrax/my/collections_controller_spec.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+RSpec.describe Hyrax::My::CollectionsController, type: :controller do
+  describe "#configure_facets" do
+    subject { controller.blacklight_config.sort_fields.keys }
+
+    let(:expected_sort_fields) do
+      [
+        "system_modified_dtsi desc",
+        "system_modified_dtsi asc",
+        "system_create_dtsi desc",
+        "system_create_dtsi asc",
+        "depositor_ssi asc, title_ssi asc",
+        "depositor_ssi desc, title_ssi desc",
+        "creator_ssi asc, title_ssi asc",
+        "creator_ssi desc, title_ssi desc"
+      ]
+    end
+
+    it "configures the custom sort fields" do
+      expect(subject).to match_array(expected_sort_fields)
+    end
+  end
+end