Fix for ActiveStorage::Attached::Many

lib/simple_form/form_builder.rb

@@ -591,6 +591,7 @@ module SimpleForm
     # Returns a Boolean.
     def file_method?(attribute_name)
       @object.respond_to?("#{attribute_name}_attachment") ||
+        @object.respond_to?("#{attribute_name}_attachments") ||
         @object.respond_to?("remote_#{attribute_name}_url") ||
         @object.respond_to?("#{attribute_name}_attacher") ||
         @object.respond_to?("#{attribute_name}_file_name")

test/form_builder/general_test.rb

@@ -244,6 +244,11 @@ class FormBuilderTest < ActionView::TestCase
     assert_select 'form input#user_with_attachment_avatar.file'
   end
 
+  test 'builder generates file input for ActiveStorage::Attached::Many' do
+    with_form_for UserWithAttachment.build, :avatars
+    assert_select 'form input#user_with_attachment_avatars.file'
+  end
+
   test 'builder generates file input for Refile >= 0.3.0 and CarrierWave >= 0.2.2' do
     with_form_for UserWithAttachment.build, :cover
     assert_select 'form input#user_with_attachment_cover.file'

test/support/models.rb

@@ -339,6 +339,10 @@ class UserWithAttachment < User
     OpenStruct.new
   end
 
+  def avatars_attachments
+    OpenStruct.new
+  end
+
   def remote_cover_url
     "/uploads/cover.png"
   end