Fix MultipleActiveStorage field deleting attachments in Rails 7.0

Fixes #3520

Author: mshibuya

lib/rails_admin/config/fields/types/multiple_active_storage.rb

@@ -14,6 +14,10 @@ class ActiveStorageAttachment < RailsAdmin::Config::Fields::Types::MultipleFileU
               {resize_to_limit: [100, 100]}
             end
 
+            register_instance_option :keep_value do
+              value.signed_id
+            end
+
             register_instance_option :delete_value do
               value.id
             end
@@ -43,6 +47,10 @@ def resource_url(thumb = false)
             ActiveStorageAttachment
           end
 
+          register_instance_option :keep_method do
+            method_name if ::ActiveStorage.replace_on_assign_to_many
+          end
+
           register_instance_option :delete_method do
             "remove_#{name}" if bindings[:object].respond_to?("remove_#{name}")
           end

spec/dummy_app/config/application.rb

@@ -38,5 +38,6 @@ class Application < Rails::Application
     config.i18n.load_path += Dir[Rails.root.join('app', 'locales', '*.{rb,yml}').to_s]
     config.active_record.time_zone_aware_types = %i[datetime time] if CI_ORM == :active_record
     config.active_storage.service = :local if defined?(ActiveStorage)
+    config.active_storage.replace_on_assign_to_many = false if defined?(ActiveStorage) && ActiveStorage.version < Gem::Version.create('6.1')
   end
 end

spec/integration/fields/multiple_active_storage_spec.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'MultipleActiveStorage field', type: :request, active_record: true do
+  subject { page }
+  before do
+    RailsAdmin.config FieldTest do
+      edit do
+        field :active_storage_assets
+      end
+    end
+    # To suppress 'SQLite3::BusyException: database is locked' exception
+    @original = page.driver.browser.url_blacklist # rubocop:disable Naming/InclusiveLanguage
+    page.driver.browser.url_blacklist = ['/rails/active_storage/'] # rubocop:disable Naming/InclusiveLanguage
+  end
+  after { page.driver.browser.url_blacklist = @original } # rubocop:disable Naming/InclusiveLanguage
+
+  it 'supports uploading multiple files', js: true do
+    visit new_path(model_name: 'field_test')
+    attach_file 'Active storage assets', [file_path('test.jpg'), file_path('test.png')]
+    click_button 'Save'
+    is_expected.to have_content 'Field test successfully created'
+    expect(FieldTest.first.active_storage_assets.map { |image| image.filename.to_s }).to match_array ['test.jpg', 'test.png']
+  end
+
+  context 'when working with existing files' do
+    let(:field_test) { FactoryBot.create(:field_test, active_storage_assets: ['test.jpg', 'test.png'].map { |img| {io: File.open(file_path(img)), filename: img} }) }
+
+    it 'supports appending a file', js: true do
+      visit edit_path(model_name: 'field_test', id: field_test.id)
+      attach_file 'Active storage assets', [file_path('test.gif')]
+      click_button 'Save'
+      is_expected.to have_content 'Field test successfully updated'
+      field_test.reload
+      expect(field_test.active_storage_assets.map { |image| image.filename.to_s }).to eq ['test.jpg', 'test.png', 'test.gif']
+    end
+
+    it 'supports deleting a file', js: true do
+      visit edit_path(model_name: 'field_test', id: field_test.id)
+      click_link "Delete 'Active storage assets' #1"
+      click_button 'Save'
+      is_expected.to have_content 'Field test successfully updated'
+      field_test.reload
+      expect(field_test.active_storage_assets.map { |image| image.filename.to_s }).to eq ['test.png']
+    end
+  end
+end