feat(combobox): reuse CheckboxGroup for required ComboboxCheckbox

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: pierry01

docs/app/views/docs/combobox.rb

@@ -123,6 +123,49 @@ def view_template
         RUBY
       end
 
+      render Docs::VisualCodeExample.new(title: "Required Checkbox", context: self) do
+        <<~RUBY
+          form(class: "flex flex-col gap-2 w-96") do
+            FormField do
+              FormFieldLabel { "Pick at least one" }
+
+              Combobox term: "things" do
+                ComboboxTrigger placeholder: "Pick value"
+
+                ComboboxPopover do
+                  ComboboxSearchInput(placeholder: "Pick value or type anything")
+
+                  ComboboxList do
+                    ComboboxEmptyState { "No result" }
+
+                    CheckboxGroup(data_required: true) do
+                      ComboboxItem do
+                        ComboboxCheckbox(name: "food[]", value: "apple", data: {value_missing: "Pick at least one option"})
+                        span { "Apple" }
+                      end
+
+                      ComboboxItem do
+                        ComboboxCheckbox(name: "food[]", value: "banana", data: {value_missing: "Pick at least one option"})
+                        span { "Banana" }
+                      end
+
+                      ComboboxItem do
+                        ComboboxCheckbox(name: "food[]", value: "carrot", data: {value_missing: "Pick at least one option"})
+                        span { "Carrot" }
+                      end
+                    end
+                  end
+                end
+              end
+
+              FormFieldError()
+            end
+
+            Button(type: "submit") { "Submit" }
+          end
+        RUBY
+      end
+
       render Docs::VisualCodeExample.new(title: "Disabled", context: self) do
         <<~RUBY
           div(class: "w-96") do

gem/lib/ruby_ui/combobox/combobox_checkbox.rb

@@ -19,7 +19,14 @@ def default_attrs
         ],
         data: {
           ruby_ui__combobox_target: "input",
-          action: "ruby-ui--combobox#inputChanged"
+          ruby_ui__checkbox_group_target: "checkbox",
+          ruby_ui__form_field_target: "input",
+          action: %w[
+            ruby-ui--combobox#inputChanged
+            change->ruby-ui--checkbox-group#onChange
+            change->ruby-ui--form-field#onInput
+            invalid->ruby-ui--form-field#onInvalid
+          ]
         }
       }
     end

gem/test/ruby_ui/combobox_test.rb

@@ -92,6 +92,15 @@ def test_combobox_checkbox_renders_styled_input
     assert_match(/checked:bg-primary/, output)
   end
 
+  def test_combobox_checkbox_wires_checkbox_group_and_form_field
+    output = phlex { RubyUI.ComboboxCheckbox(name: "x", value: "1") }
+    assert_match(/data-ruby-ui--checkbox-group-target="checkbox"/, output)
+    assert_match(/data-ruby-ui--form-field-target="input"/, output)
+    assert_match(/change->ruby-ui--checkbox-group#onChange/, output)
+    assert_match(/change->ruby-ui--form-field#onInput/, output)
+    assert_match(/invalid->ruby-ui--form-field#onInvalid/, output)
+  end
+
   def test_combobox_item_indicator_renders_check_svg
     output = phlex { RubyUI.ComboboxItemIndicator() }
     assert_match(/peer-checked:opacity-100/, output)