Reload configuration on change in development mode

Fixes railsadminteam#2726, Fixes railsadminteam#3025

Author: mshibuya

config/initializers/active_record_extensions.rb

@@ -2,7 +2,9 @@
   module ActiveRecord
     class Base
       def self.rails_admin(&block)
-        RailsAdmin.config(self, &block)
+        RailsAdmin.config do |config|
+          config.model(self, &block)
+        end
       end
 
       def rails_admin_default_object_label_method

lib/rails_admin.rb

@@ -27,7 +27,7 @@ def self.config(entity = nil, &block)
     if entity
       RailsAdmin::Config.model(entity, &block)
     elsif block_given?
-      block.call(RailsAdmin::Config)
+      RailsAdmin::Config.apply(&block)
     else
       RailsAdmin::Config
     end

lib/rails_admin/abstract_model.rb

@@ -19,7 +19,7 @@ def all(adapter = nil)
       def new(m)
         m = m.constantize unless m.is_a?(Class)
         (am = old_new(m)).model && am.adapter ? am : nil
-      rescue LoadError, NameError
+      rescue *([LoadError, NameError] + (defined?(ActiveRecord) ? ['ActiveRecord::NoDatabaseError'.constantize] : []))
         puts "[RailsAdmin] Could not load model #{m}, assuming model is non existing. (#{$ERROR_INFO})" unless Rails.env.test?
         nil
       end

lib/rails_admin/adapters/mongoid/extension.rb

@@ -9,7 +9,9 @@ module Extension
           self.nested_attributes_options = {}
           class << self
             def rails_admin(&block)
-              RailsAdmin.config(self, &block)
+              RailsAdmin.config do |config|
+                config.model(self, &block)
+              end
             end
 
             alias_method :accepts_nested_attributes_for_without_rails_admin, :accepts_nested_attributes_for

lib/rails_admin/config.rb

@@ -1,4 +1,4 @@
-require 'rails_admin/config/lazy_model'
+require 'rails_admin/config/model'
 require 'rails_admin/config/sections/list'
 require 'active_support/core_ext/module/attribute_accessors'
 
@@ -20,6 +20,10 @@ module Config
 
     DEFAULT_CURRENT_USER = proc {}
 
+    # Variables to track initialization process
+    @initialized = false
+    @deferred_blocks = []
+
     class << self
       # Application title, can be an array of two elements
       attr_accessor :main_app_name
@@ -82,6 +86,22 @@ class << self
       attr_accessor :navigation_static_links
       attr_accessor :navigation_static_label
 
+      # Finish initialization by executing deferred configuration blocks
+      def initialize!
+        @deferred_blocks.each { |block| block.call(self) }
+        @deferred_blocks.clear
+        @initialized = true
+      end
+
+      # Evaluate the given block either immediately or lazily, based on initialization status.
+      def apply(&block)
+        if @initialized
+          block.call(self)
+        else
+          @deferred_blocks << block
+        end
+      end
+
       # Setup authentication to be run as a before filter
       # This is run inside the controller instance so you can setup any authentication you need to
       #
@@ -235,8 +255,8 @@ def model(entity, &block)
           end
         end
 
-        @registry[key] ||= RailsAdmin::Config::LazyModel.new(entity)
-        @registry[key].add_deferred_block(&block) if block
+        @registry[key] ||= RailsAdmin::Config::Model.new(entity)
+        @registry[key].instance_eval(&block) if block && @registry[key].abstract_model
         @registry[key]
       end
 
@@ -311,10 +331,17 @@ def reset_all_models
         @registry = {}
       end
 
+      # Perform reset, then load RailsAdmin initializer again
+      def reload!
+        @initialized = false
+        reset
+        load RailsAdmin::Engine.config.initializer_path
+        initialize!
+      end
+
       # Get all models that are configured as visible sorted by their weight and label.
       #
       # @see RailsAdmin::Config::Hideable
-
       def visible_models(bindings)
         visible_models_with_bindings(bindings).sort do |a, b|
           if (weight_order = a.weight <=> b.weight) == 0

lib/rails_admin/config/lazy_model.rb

@@ -24,11 +24,23 @@ class Engine < Rails::Engine
       app.config.middleware.use Rack::Pjax
     end
 
-    initializer 'RailsAdmin reload config in development' do
-      if Rails.application.config.cache_classes
+    initializer 'RailsAdmin reload config in development' do |app|
+      config.initializer_path = app.root.join('config/initializers/rails_admin.rb')
+
+      unless Rails.application.config.cache_classes
         ActiveSupport::Reloader.before_class_unload do
-          RailsAdmin::Config.reset_all_models
+          RailsAdmin::Config.reload!
+        end
+
+        reloader = app.config.file_watcher.new([config.initializer_path], []) do
+          # Do nothing, ActiveSupport::Reloader will trigger class_unload! anyway
         end
+
+        app.reloaders << reloader
+        app.reloader.to_run do
+          reloader.execute_if_updated { require_unload_lock! }
+        end
+        reloader.execute
       end
     end
 
@@ -57,6 +69,8 @@ class Engine < Rails::Engine
           to config/application.rb.
         EOM
       end
+
+      RailsAdmin::Config.initialize!
     end
   end
 end

lib/rails_admin/engine.rb

@@ -11,6 +11,18 @@
     end
   end
 
+  describe '.new' do
+    context 'on ActiveRecord::NoDatabaseError', active_record: true do
+      before do
+        expect(WithoutTable).to receive(:table_exists?).and_raise(ActiveRecord::NoDatabaseError)
+      end
+
+      it 'does not raise error and returns nil' do
+        expect(RailsAdmin::AbstractModel.new('WithoutTable')).to eq nil
+      end
+    end
+  end
+
   describe '#to_s' do
     it 'returns model\'s name' do
       expect(RailsAdmin::AbstractModel.new(Cms::BasicPage).to_s).to eq Cms::BasicPage.to_s

spec/rails_admin/abstract_model_spec.rb

@@ -51,4 +51,24 @@
 
     expect(RailsAdmin.config(Team).fields.map(&:name)).to eql(original_fields_order)
   end
+
+  describe '#_fields' do
+    let(:config) { RailsAdmin.config(Team) }
+    before do
+      RailsAdmin.config(Team) do
+        field :id
+        field :wins, :boolean
+      end
+    end
+
+    it "does not cause FrozenError by changing exiting field's tye" do
+      # Reference the fields for readonly
+      config.edit.send(:_fields, true)
+
+      RailsAdmin.config(Team) do
+        field :wins, :integer
+      end
+      expect(config.fields.map(&:name)).to match_array %i(id wins)
+    end
+  end
 end