Support filtering has_one associations

lib/rails_admin/adapters/mongoid.rb

@@ -201,7 +201,7 @@ def perform_search_on_associated_collection(field_name, conditions)
         case target_association.type
         when :belongs_to, :has_and_belongs_to_many
           [{target_association.foreign_key.to_s => {'$in' => model.where('$or' => conditions).all.collect { |r| r.send(target_association.primary_key) }}}]
-        when :has_many
+        when :has_many, :has_one
           [{target_association.primary_key.to_s => {'$in' => model.where('$or' => conditions).all.collect { |r| r.send(target_association.foreign_key) }}}]
         end
       end

spec/integration/actions/index_spec.rb

@@ -135,6 +135,22 @@
       is_expected.to have_no_content(@players[3].name)
     end
 
+    it 'allows to filter on has_one relationships' do
+      @draft = FactoryBot.create(:draft, player: @players[1], college: 'University of Alabama')
+      RailsAdmin.config Player do
+        list do
+          field :name
+          field :draft do
+            searchable :college
+          end
+        end
+      end
+
+      visit index_path(model_name: 'player', f: {draft: {'1' => {v: 'Alabama'}}})
+      is_expected.to have_content(@players[1].name)
+      is_expected.to have_css('tbody .name_field', count: 1)
+    end
+
     it 'allows to disable search on attributes' do
       RailsAdmin.config Player do
         list do

spec/integration/widgets/filter_box_spec.rb

@@ -157,4 +157,22 @@
       expect(find('[name^="f[time_field]"][name$="[v][]"]', match: :first, visible: false).value).to eq '2000-01-01T14:00:00'
     end
   end
+
+  describe 'for has_one association field' do
+    before do
+      RailsAdmin.config Player do
+        field :draft do
+          searchable :college
+        end
+      end
+    end
+
+    it 'is filterable' do
+      visit index_path(model_name: 'player')
+      click_link 'Add filter'
+      click_link 'Draft'
+      expect(page).to have_css '[name^="f[draft]"][name$="[o]"]'
+      expect(page).to have_css '[name^="f[draft]"][name$="[v]"]'
+    end
+  end
 end

src/rails_admin/filter-box.js

@@ -169,6 +169,7 @@ import flatpickr from "flatpickr";
         case "string":
         case "text":
         case "belongs_to_association":
+        case "has_one_association":
           control = $(
             '<select class="switch-additional-fieldsets form-control form-control-sm"></select>'
           )