Use a current model to provide the host for service urls

Trying to pass the current request down to the service so that it can
create full urls instead of paths makes the API messy so use a model
based on ActiveSupport::CurrentAttributes to provide the current host
to services that need it (primarily the disk service).

activestorage/app/controllers/active_storage/base_controller.rb

@@ -3,4 +3,8 @@
 # The base controller for all ActiveStorage controllers.
 class ActiveStorage::BaseController < ActionController::Base
   protect_from_forgery with: :exception
+
+  before_action do
+    ActiveStorage::Current.host = request.base_url
+  end
 end

activestorage/app/models/active_storage/current.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ActiveStorage::Current < ActiveSupport::CurrentAttributes #:nodoc:
+  attribute :host
+end

activestorage/lib/active_storage/service/disk_service.rb

@@ -78,8 +78,9 @@ module ActiveStorage
         verified_key_with_expiration = ActiveStorage.verifier.generate(key, expires_in: expires_in, purpose: :blob_key)
 
         generated_url =
-          url_helpers.rails_disk_service_path(
+          url_helpers.rails_disk_service_url(
             verified_key_with_expiration,
+            host: current_host,
             filename: filename,
             disposition: content_disposition_with(type: disposition, filename: filename),
             content_type: content_type
@@ -104,7 +105,7 @@ module ActiveStorage
           purpose: :blob_token }
         )
 
-        generated_url = url_helpers.update_rails_disk_service_path(verified_token_with_expiration)
+        generated_url = url_helpers.update_rails_disk_service_url(verified_token_with_expiration, host: current_host)
 
         payload[:url] = generated_url
 
@@ -129,7 +130,6 @@ module ActiveStorage
         path_for(key).tap { |path| FileUtils.mkdir_p File.dirname(path) }
       end
 
-
       def ensure_integrity_of(key, checksum)
         unless Digest::MD5.file(path_for(key)).base64digest == checksum
           delete key
@@ -137,9 +137,12 @@ module ActiveStorage
         end
       end
 
-
       def url_helpers
         @url_helpers ||= Rails.application.routes.url_helpers
       end
+
+      def current_host
+        ActiveStorage::Current.host
+      end
   end
 end

activestorage/test/models/blob_test.rb

@@ -140,6 +140,6 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     def expected_url_for(blob, disposition: :inline, filename: nil)
       filename ||= blob.filename
       query_string = { content_type: blob.content_type, disposition: "#{disposition}; #{filename.parameters}" }.to_param
-      "/rails/active_storage/disk/#{ActiveStorage.verifier.generate(blob.key, expires_in: 5.minutes, purpose: :blob_key)}/#{filename}?#{query_string}"
+      "https://example.com/rails/active_storage/disk/#{ActiveStorage.verifier.generate(blob.key, expires_in: 5.minutes, purpose: :blob_key)}/#{filename}?#{query_string}"
     end
 end

activestorage/test/service/disk_service_test.rb

@@ -8,7 +8,7 @@ class ActiveStorage::Service::DiskServiceTest < ActiveSupport::TestCase
   include ActiveStorage::Service::SharedServiceTests
 
   test "url generation" do
-    assert_match(/rails\/active_storage\/disk\/.*\/avatar\.png\?content_type=image%2Fpng&disposition=inline/,
+    assert_match(/^https:\/\/example.com\/rails\/active_storage\/disk\/.*\/avatar\.png\?content_type=image%2Fpng&disposition=inline/,
       @service.url(FIXTURE_KEY, expires_in: 5.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png"))
   end
 end

activestorage/test/test_helper.rb

@@ -41,6 +41,14 @@ ActiveStorage.verifier = ActiveSupport::MessageVerifier.new("Testing")
 class ActiveSupport::TestCase
   self.file_fixture_path = File.expand_path("fixtures/files", __dir__)
 
+  setup do
+    ActiveStorage::Current.host = "https://example.com"
+  end
+
+  teardown do
+    ActiveStorage::Current.reset
+  end
+
   private
     def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain")
       ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type