ActiveAdmin::Resource looks up classes at runtime using their name

To deal with the reloading issues in activeadmin#870, we now store reference to the
resource class as a string and constantize it each time we need it.

Also added a new cucumber profile called "class-reloading" which does
not cache classes. Since Active Admin should always work as expected in
development with Rails reloading, we should continue to grow scenarios
that include the '@requires-reloading' tag.

cucumber.yml

@@ -1,2 +1,3 @@
-default: --format 'progress' --require features/support/env.rb --require features/step_definitions features
-wip: --format 'progress' --require features/support/env.rb --require features/step_definitions features --tags @wip:3 --wip features
+default: --format 'progress' --require features/support/env.rb --require features/step_definitions features --tags ~@requires-reloading
+wip: --format 'progress' --require features/support/env.rb --require features/step_definitions features --tags @wip:3 --wip features
+class-reloading: RAILS_ENV=cucumber_with_reloading --format 'progress' --require features/support/env.rb --require features/step_definitions features --tags @requires-reloading

features/development_reloading.feature

@@ -0,0 +1,19 @@
+Feature: Development Reloading
+
+  In order to quickly develop applications
+  As a developer
+  I want the application to reload itself in development
+
+  @requires-reloading
+  Scenario: Reloading an updated model that a resource points to
+    Given a configuration of:
+    """
+      ActiveAdmin.register Post
+    """
+    And I am logged in
+    And I create a new post with the title ""
+    Then I should see a successful create flash
+    Given I add "validates_presence_of :title" to the "post" model
+    And I create a new post with the title ""
+    Then I should not see a successful create flash
+    And I should see a validation error "can't be blank"

features/step_definitions/additional_web_steps.rb

@@ -80,3 +80,6 @@
   page.should have_css("#active_admin_content", :text => content)
 end
 
+Then /^I should see a validation error "([^"]*)"$/ do |error_message|
+  page.should have_css(".inline-errors", :text => error_message)
+end

features/step_definitions/configuration_steps.rb

@@ -9,8 +9,35 @@ def load_active_admin_configuration(configuration_content)
 
 end
 
+module ActiveAdminContentsRollback
+
+  def self.recorded_files
+    @files ||= {}
+  end
+
+  # Records the contents of a file the first time we are
+  # about to change it
+  def self.record(filename)
+    recorded_files[filename] ||= File.read(filename)
+  end
+
+  # Rolls the recorded files back to their original states
+  def self.rollback!
+    recorded_files.each do |filename, contents|
+      File.open(filename, "w+") do |f|
+        f << contents
+      end
+    end
+  end
+
+end
+
 World(ActiveAdminReloading)
 
+After do
+  ActiveAdminContentsRollback.rollback!
+end
+
 Given /^a configuration of:$/ do |configuration_content|
   load_active_admin_configuration(configuration_content)
   ActiveAdmin.application.namespaces.values.each{|n| n.load_menu! }
@@ -37,3 +64,16 @@ def load_active_admin_configuration(configuration_content)
   FileUtils.mkdir_p File.dirname(filepath)
   File.open(filepath, 'w+'){|f| f << contents }
 end
+
+Given /^I add "([^"]*)" to the "([^"]*)" model$/ do |code, model_name|
+  filename = File.join(Rails.root, "app", "models", "#{model_name}.rb")
+  ActiveAdminContentsRollback.record(filename)
+
+  # Update the file
+  contents = File.read(filename)
+  File.open(filename, "w+") do |f|
+    f << contents.gsub(/^(class .+)$/, "\\1\n  #{code}\n")
+  end
+
+  ActiveSupport::Dependencies.clear
+end

features/step_definitions/flash_steps.rb

@@ -1,3 +1,11 @@
 Then /^I should see a flash with "([^"]*)"$/ do |text|
-  Then %{I should see "#{text}"}
+  page.should have_content(text)
+end
+
+Then /^I should see a successful create flash$/ do
+  page.should have_css('div.flash_notice', :text => /was successfully created/)
+end
+
+Then /^I should not see a successful create flash$/ do
+  page.should_not have_css('div.flash_notice', :text => /was successfully created/)
 end

lib/active_admin/resource.rb

@@ -25,9 +25,8 @@ class Resource
     # The namespace this config belongs to
     attr_reader :namespace
 
-    # The class this resource wraps. If you register the Post model, Resource#resource
-    # will point to the Post class
-    attr_reader :resource_class
+    # The name of the resource class
+    attr_reader :resource_class_name
 
     # An array of member actions defined for this resource
     attr_reader :member_actions
@@ -50,7 +49,7 @@ class Resource
     module Base
       def initialize(namespace, resource_class, options = {})
         @namespace = namespace
-        @resource_class = resource_class
+        @resource_class_name = "::#{resource_class.name}"
         @options = default_options.merge(options)
         @sort_order = @options[:sort_order]
         @member_actions, @collection_actions = [], []
@@ -66,6 +65,12 @@ def initialize(namespace, resource_class, options = {})
     include Sidebars
     include Menu
 
+    # The class this resource wraps. If you register the Post model, Resource#resource_class
+    # will point to the Post class
+    def resource_class
+      ActiveSupport::Dependencies.constantize(resource_class_name)
+    end
+
     def resource_table_name
       resource_class.quoted_table_name
     end

lib/active_admin/resource_controller.rb

@@ -5,6 +5,7 @@
 require 'active_admin/resource_controller/collection'
 require 'active_admin/resource_controller/filters'
 require 'active_admin/resource_controller/scoping'
+require 'active_admin/resource_controller/resource_class_methods'
 
 module ActiveAdmin
   # All Resources Controller inherits from this controller.
@@ -23,15 +24,25 @@ class ResourceController < BaseController
     include Collection
     include Filters
     include Scoping
+    extend  ResourceClassMethods
 
     class << self
       def active_admin_config=(config)
         @active_admin_config = config
+
         defaults  :resource_class => config.resource_class,
                   :route_prefix => config.route_prefix,
                   :instance_name => config.underscored_resource_name
       end
 
+      # Inherited Resources uses the inherited(base) hook method to 
+      # add in the Base.resource_class class method. To override it, we
+      # need to install our resource_class method each time we're inherited from.
+      def inherited(base)
+        super(base)
+        base.override_resource_class_methods!
+      end
+
       public :belongs_to
     end
 

lib/active_admin/resource_controller/resource_class_methods.rb

@@ -0,0 +1,24 @@
+module ActiveAdmin
+  class ResourceController < BaseController
+    module ResourceClassMethods
+
+      # Override the default resource_class class and instance
+      # methods to only return the class defined in the instance
+      # of ActiveAdmin::Resource
+      def override_resource_class_methods!
+        self.class_eval do
+          def self.resource_class=(klass); end
+
+          def self.resource_class
+            @active_admin_config ? @active_admin_config.resource_class : nil
+          end
+
+          def resource_class
+            self.class.resource_class
+          end
+        end
+      end
+
+    end
+  end
+end

spec/spec_helper.rb

@@ -90,6 +90,10 @@ def mock_action_view(assigns = {})
   end  
   alias_method :action_view, :mock_action_view
 
+  # A mock resource to register
+  class MockResource
+  end
+
 end
 
 ENV['RAILS_ENV'] = 'test'

spec/support/rails_template.rb

@@ -2,8 +2,11 @@
 
 # Create a cucumber database and environment
 copy_file File.expand_path('../templates/cucumber.rb', __FILE__), "config/environments/cucumber.rb"
+copy_file File.expand_path('../templates/cucumber_with_reloading.rb', __FILE__), "config/environments/cucumber_with_reloading.rb"
+
 gsub_file 'config/database.yml', /^test:.*\n/, "test: &test\n"
 gsub_file 'config/database.yml', /\z/, "\ncucumber:\n  <<: *test\n  database: db/cucumber.sqlite3"
+gsub_file 'config/database.yml', /\z/, "\ncucumber_with_reloading:\n  <<: *test\n  database: db/cucumber.sqlite3"
 
 # Generate some test models
 generate :model, "post title:string body:text published_at:datetime author_id:integer category_id:integer"

spec/support/templates/cucumber_with_reloading.rb

@@ -0,0 +1,5 @@
+require File.expand_path('config/environments/cucumber', Rails.root)
+
+Rails.application.class.configure do
+  config.cache_classes = false
+end

spec/unit/namespace/register_resource_spec.rb

@@ -52,6 +52,7 @@ module ::Mock; class Resource; def self.has_many(arg1, arg2); end; end; end
       namespace.load_menu!
       namespace.menu["Mock Resources"].should be_an_instance_of(ActiveAdmin::MenuItem)
     end
+
     it "should use the resource as the model in the controller" do
       Admin::MockResourcesController.resource_class.should == Mock::Resource
     end

spec/unit/resource_spec.rb

@@ -200,17 +200,15 @@ class ::News; def self.has_many(*); end end
 
       context "when resource class responds to primary_key" do
         it "should sort by primary key desc by default" do
-          mock_resource = mock
-          mock_resource.should_receive(:primary_key).and_return("pk")
-          config = Resource.new(namespace, mock_resource)
+          MockResource.should_receive(:primary_key).and_return("pk")
+          config = Resource.new(namespace, MockResource)
           config.sort_order.should == "pk_desc"
         end
       end
 
       context "when resource class does not respond to primary_key" do
         it "should default to id" do
-          mock_resource = mock
-          config = Resource.new(namespace, mock_resource)
+          config = Resource.new(namespace, MockResource)
           config.sort_order.should == "id_desc"
         end
       end

tasks/test.rake

@@ -7,7 +7,7 @@ end
 
 # Run specs and cukes
 desc "Run the full suite"
-task :test => ['spec:unit', 'spec:integration', 'cucumber']
+task :test => ['spec:unit', 'spec:integration', 'cucumber', 'cucumber:class_reloading']
 
 namespace :test do
 
@@ -28,6 +28,7 @@ namespace :test do
       cmd "export RAILS=#{version} && bundle exec rspec spec/unit"
       cmd "export RAILS=#{version} && bundle exec rspec spec/integration"
       cmd "export RAILS=#{version} && bundle exec cucumber features"
+      cmd "export RAILS=#{version} && bundle exec cucumber -p class-reloading features"
     end
     cmd "./script/use_rails #{current_version}" if current_version
   end
@@ -65,4 +66,8 @@ namespace :cucumber do
     t.profile = 'wip'
   end
 
+  Cucumber::Rake::Task.new(:class_reloading, "Run the cucumber scenarios that test reloading") do |t|
+    t.profile = 'class-reloading'
+  end
+
 end