Alchemy doesn't respect RAILS_RELATIVE_URL_ROOT

[dssjoblom]

Steps to reproduce

Configure Rails with a relative URL root. https://guides.rubyonrails.org/configuring.html#deploy-to-a-subdirectory-relative-url-root

Expected behavior

Alchemy should only use URLs with the specified root.

Actual behavior

The preview window attempts to access the non-relative root /. For example, assume RAILS_RELATIVE_URL_ROOT is "/subdir" and Alchemy is mounted on "cms". The preview will then attempt to load e.g. /cms/admin/pages/1, which doesn't exist, while it should instead load /subdir/cms/admin/pages/1. It is possible this same issue is present in other parts of the code as well.

System configuration

• Alchemy Version: 6.0.0-rc6
• Rails Version: 6.1.4.7

[tvdeyen]

Yeah, another issue were engines do not know where they are mounted at 🤷🏻 Engines are kind of a step child for the Rails team.

That said, you can, though, register your own preview url - even several sources admins can select from are possible.

alchemy_cms/lib/alchemy/admin/preview_url.rb

Lines 14 to 32 in 12e8a4f

	# == Example config/alchemy/config.yml
	#
	# preview:
	# host: https://www.my-static-site.com
	# auth:
	# username: <%= ENV["BASIC_AUTH_USERNAME"] %>
	# password: <%= ENV["BASIC_AUTH_PASSWORD"] %>
	#
	# Preview config per site is supported as well.
	#
	# == Example config/alchemy/config.yml
	#
	# preview:
	# My site name:
	# host: https://www.my-static-site.com
	# auth:
	# username: <%= ENV["BASIC_AUTH_USERNAME"] %>
	# password: <%= ENV["BASIC_AUTH_PASSWORD"] %>
	#

alchemy_cms/lib/alchemy.rb

Lines 8 to 36 in 12e8a4f

	# Define page preview sources
	#
	# A preview source is a Ruby class returning an URL
	# that is used as source for the preview frame in the
	# admin UI.
	#
	# == Example
	#
	# # lib/acme/preview_source.rb
	# class Acme::PreviewSource < Alchemy::Admin::PreviewUrl
	# def url_for(page)
	# if page.site.name == "Next"
	# "https://user:#{ENV['PREVIEW_HTTP_PASS']}@next.acme.com"
	# else
	# "https://www.acme.com"
	# end
	# end
	# end
	#
	# # config/initializers/alchemy.rb
	# require "acme/preview_source"
	# Alchemy.preview_sources << Acme::PreviewSource
	#
	# # config/locales/de.yml
	# de:
	# activemodel:
	# models:
	# acme/preview_source: Acme Vorschau
	#