file_field helper raises an exception if attribute does not match an active storage attachment

[brenogazzola]

Steps to reproduce

model Gallery
  has_many_attached :images
end

<%= form_with model: Gallery.new do |form| %>
  <%= form.file_field :image, direct_upload: true %>
<% end %>

ActionView::Template::Error (undefined method `options' for nil:NilClass):

In this case the attachment is called images, but we passed the atribute image. The bug was introduced in PR #38957, which added per attachment service. The problem happens because this line:

attachment_reflection = options[:object].class.reflect_on_attachment(name)

... ends with attachment_reflection = nil and then this line:

service_name = attachment_reflection.options[:service_name] || ActiveStorage::Blob.service.name

... causes the nil exception.

Expected behavior

The page is rendered using the default service

Actual behavior

An exception is raised.

System configuration

Rails version: 193289d
Ruby version: 3.0.2

cc: @DmitryTsepelev @gmcgibbon

[brenogazzola]

Fixed by #44287