Missing host to link to error in Rails 5.2.1 - ruby-on-rails

Question

I've gone through every stackoverflow question regarding this error:
https://duckduckgo.com/?q=rails+Missing+host+to+link+to
All the posts mention the same solution, which is to add the config in the environment file you're working on. In my case, I added to my development.rb:
config.active_storage.service = :local
config.action_mailer.default_url_options = { host: "localhost", port: "3000" }
MyApp::Application.default_url_options = Robson::Application.config.action_mailer.default_url_options
Rails.application.routes.default_url_options = Robson::Application.config.action_mailer.default_url_options
But I still get the infamous error message:
Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
In the following locations if I try to open a file that I uploaded locally:
open(file.service_url)
or if I try to access the files from ActiveAdmin (I called the model "Attachments" and I'm using ActiveStorage)
column(:file) {|a| link_to a.file.filename, a.file.service_url}
I also tried setting "host" in a dictionary as a parameter in the above "link_to" and "open" functions. I also tried "only_path".
Nothing works.
Any help would be appreciated!
P.S.: my active storage config:
local:
service: Disk
root: <%= Rails.root.join("storage") %>
test:
service: Disk
root: <%= Rails.root.join("tmp/storage") %>
amazon:
service: S3
access_key_id: S3_ACCESS_KEY_ID
secret_access_key: S3_SECRET_ACCESS_KEY
bucket: S3_BUCKET
region: S3_REGION
UPDATE
Trying to use rails_representation_url but getting an error undefined method 'variation' for ActiveStorage::Attached
class Attachment < ApplicationRecord
include Rails.application.routes.url_helpers
has_one_attached :file
....
def with_uploaded_file
tempfile = Tempfile.open([file.filename.to_s, File.extname(file.filename.to_s)]) do |file_temp|
file_temp.binmode unless file.content_type =~ /text/
require 'open-uri'
# file_temp.write(open(file.service_url).read)
file_temp.write(open(rails_representation_url(file, only_path: true)).read)
file_temp
end
begin
yield(tempfile)
ensure
tempfile.unlink
end

Answer 1

I upgraded Rails from 5.1 to 5.2 and had same problem.
Solution: https://github.com/rails/rails/issues/32866
So when you have your ActiveRecord variant instead of
variant.service_url
do
rails_representation_url(variant, only_path: true)