Support ActiveStorage on Rails 5.2

lib/simple_form/form_builder.rb

@@ -579,7 +579,9 @@ def file_method?(attribute_name)
     end
 
     def activestorage?(attribute_name)
-      @object.class.try(:reflect_on_attachment, attribute_name).present?
+      @object.class.try(:reflect_on_attachment, attribute_name).present? ||
+        @object.class.try(:reflect_on_association, "#{attribute_name}_attachment").present? ||
+        @object.class.try(:reflect_on_association, "#{attribute_name}_attachments").present?
     end
 
     def shrine?(attribute_name)

test/form_builder/general_test.rb

@@ -244,6 +244,16 @@ def with_custom_form_for(object, *args, &block)
     assert_select 'form input#user_with_attachment_avatar.file'
   end
 
+  test 'builder generates file input for activestorage in Rails 5.2' do
+    with_form_for UserWithAttachment.build, :image
+    assert_select 'form input#user_with_attachment_image.file'
+  end
+
+  test 'builder generates file input for activestorage in Rails 5.2 with multiple files' do
+    with_form_for UserWithAttachment.build, :images
+    assert_select 'form input#user_with_attachment_images.file'
+  end
+
   test 'builder generates file input for carrierwave' do
     with_form_for UserWithAttachment.build, :photo
     assert_select 'form input#user_with_attachment_photo.file'

test/support/models.rb

@@ -339,6 +339,10 @@ def self.reflect_on_attachment(attachment)
     OpenStruct.new if attachment == :avatar
   end
 
+  def self.reflect_on_association(association)
+    OpenStruct.new if ["image_attachment", "images_attachments"].include?(association)
+  end
+
   def photo_url
     "/photos/1.png"
   end