Add ability to specify non-existent field for combobox

app/presenters/hotwire_combobox/component.rb

@@ -204,7 +204,7 @@ def hidden_field_data
     end
 
     def hidden_field_value
-      form&.object&.public_send(name) || value
+      form&.object&.try(name) || value
     end
 
 

test/application_view_test_case.rb

@@ -10,6 +10,21 @@ def assert_attrs(tag, tag_name: :input, **attrs)
     assert_match /<#{tag_name}.* #{attrs}/, tag
   end
 
+  def mock_form(form_object: OpenStruct.new)
+    form = OpenStruct.new
+    form.define_singleton_method(:field_id) { |name| "#{name}_id" }
+    form.define_singleton_method(:field_name) { |name| name }
+    form.define_singleton_method(:object) { form_object }
+    form_object.define_singleton_method(:public_send) do |method_name, *args|
+      if form_object.respond_to?(method_name)
+        super(method_name, *args)
+      else
+        raise NoMethodError, "undefined method `#{method_name}` for #{form_object.inspect}"
+      end
+    end
+    form
+  end
+
   private
     def escape_specials(value)
       special_characters = Regexp.union "[]".chars

test/presenters/hotwire_combobox/component_test.rb

@@ -0,0 +1,49 @@
+require "test_helper"
+
+class HotwireCombobox::ComponentTest < ApplicationViewTestCase
+  setup do
+    @view = ActionView::Base.new(ActionController::Base.view_paths, {}, ActionController::Base.new)
+  end
+
+  test "hidden_field_attrs returns value from form object if available" do
+    existent_field_on_model = "Peter"
+    field_name = :name
+    component = HotwireCombobox::Component.new @view, field_name,
+      form: mock_form(form_object: OpenStruct.new("#{field_name}": existent_field_on_model))
+
+    assert_equal component.hidden_field_attrs, { id: "#{field_name}_id-hw-hidden-field",
+                                                 name: :name,
+                                                 data: { hw_combobox_target: "hiddenField" },
+                                                 value: existent_field_on_model }
+  end
+
+  test "hidden_field_attrs returns component value if not available in form object" do
+    field_name = "options[name]"
+    specified_value = "Peter"
+    component = HotwireCombobox::Component.new(
+      @view, field_name,
+      form: mock_form,
+      value: specified_value
+    )
+
+    assert_equal component.hidden_field_attrs, { id: "#{field_name}_id-hw-hidden-field",
+                                                 name: field_name,
+                                                 data: { hw_combobox_target: "hiddenField" },
+                                                 value: specified_value }
+
+  end
+
+  test "hidden_field_attrs returns nil for value if neither form object nor component value is available" do
+    field_name = "options[name]"
+    component = HotwireCombobox::Component.new(
+      @view, field_name,
+      form: mock_form,
+    )
+
+    assert_equal component.hidden_field_attrs, { id: "#{field_name}_id-hw-hidden-field",
+                                                 name: field_name,
+                                                 data: { hw_combobox_target: "hiddenField" },
+                                                 value: nil }
+
+  end
+end