Make it easier to include modules into backend class

CHANGELOG.md

@@ -6,6 +6,8 @@
   ([#536](https://github.com/shioyama/mobility/pull/536))
 - Support primary keys other then :id on model classes
   ([#542](https://github.com/shioyama/mobility/pull/542))
+- Make it easier to include modules into backend class
+  ([#538](https://github.com/shioyama/mobility/pull/538))
 
 ## 1.2
 

lib/mobility/plugin.rb

@@ -15,8 +15,14 @@ module Mobility
   used to include any module(s) into the backend class, see
   {Mobility::Plugins::Backend}.)
 
-Also includes a +configure+ class method to apply plugins to a pluggable
-({Mobility::Pluggable} instance), with a block.
+To define methods on the backend, the plugin +included+ hook also looks for
+constants named +BackendMethods+ and/or +BackendClassMethods+ in the plugin
+namespace. If it finds these, *and* no included hook has been defined on the
+plugin, then it auto-generates an included hook in which the backend class
+includes/extends these modules.
+
+The module also includes a +configure+ class method to apply plugins to a
+pluggable ({Mobility::Pluggable} instance), with a block.
 
 @example Defining a plugin
   module MyPlugin
@@ -36,6 +42,21 @@ module MyPlugin
     end
   end
 
+@example With +BackendMethods+ module
+  module MyPlugin
+    extend Mobility::Plugin
+
+    module BackendMethods
+      def read(locale, **)
+        # ...
+      end
+
+      def write(locale, value, **)
+        # ...
+      end
+    end
+  end
+
 @example Configure an attributes class with plugins
   class Translations < Mobility::Translations
   end
@@ -95,6 +116,14 @@ def included(pluggable)
       if defined?(@default) && !pluggable.defaults.has_key?(name = Plugins.lookup_name(self))
         pluggable.defaults[name] = @default
       end
+      if !method_defined?(:included) &&
+          (defined?(self::BackendMethods) || defined?(self::BackendClassMethods))
+        plugin = self
+        included_hook do |_, backend_class|
+          backend_class.include(plugin::BackendMethods) if defined?(plugin::BackendMethods)
+          backend_class.extend(plugin::BackendClassMethods) if defined?(plugin::BackendClassMethods)
+        end
+      end
       super
     end
 

lib/mobility/plugins/active_record/column_fallback.rb

@@ -13,11 +13,6 @@ module ColumnFallback
 
         requires :column_fallback, include: false
 
-        included_hook do |_, backend_class|
-          backend_class.include BackendInstanceMethods
-          backend_class.extend BackendClassMethods
-        end
-
         def self.use_column_fallback?(options, locale)
           case column_fallback = options[:column_fallback]
           when TrueClass
@@ -31,7 +26,7 @@ def self.use_column_fallback?(options, locale)
           end
         end
 
-        module BackendInstanceMethods
+        module BackendMethods
           def read(locale, **)
             if ColumnFallback.use_column_fallback?(options, locale)
               model.read_attribute(attribute)

lib/mobility/plugins/active_record/dirty.rb

@@ -51,12 +51,6 @@ module Dirty
           end
         end
 
-        included_hook do |_, backend_class|
-          if options[:dirty]
-            backend_class.include BackendMethods
-          end
-        end
-
         private
 
         def dirty_handler_methods
@@ -109,8 +103,6 @@ def reload(*)
             end
           end
         end
-
-        BackendMethods = ActiveModel::Dirty::BackendMethods
       end
     end
 

lib/mobility/plugins/default.rb

@@ -66,11 +66,6 @@ module Default
 
       requires :backend, include: :before
 
-      # Applies default plugin to attributes.
-      included_hook do |_klass, backend_class|
-        backend_class.include(BackendMethods)
-      end
-
       # Generate a default value for given parameters.
       # @param [Object, Proc] default_value A default value or Proc
       # @param [Symbol] locale

lib/mobility/plugins/fallbacks.rb

@@ -117,7 +117,7 @@ module Fallbacks
       # Applies fallbacks plugin to attributes. Completely disables fallbacks
       # on model if option is +false+.
       included_hook do |_, backend_class|
-        backend_class.include(BackendInstanceMethods) unless options[:fallbacks] == false
+        backend_class.include(BackendMethods) unless options[:fallbacks] == false
         # This is weird. We need to find a better way to allow customization of
         # rarely-customized code like this.
         backend_class.define_method(:generate_fallbacks, &method(:generate_fallbacks))
@@ -136,7 +136,7 @@ def [](locale)
         end
       end
 
-      module BackendInstanceMethods
+      module BackendMethods
         def read(locale, fallback: true, **kwargs)
           return super(locale, **kwargs) if !fallback || kwargs[:locale]
 

lib/mobility/plugins/presence.rb

@@ -18,28 +18,25 @@ module Presence
       default true
       requires :backend, include: :before
 
-      # Applies presence plugin to attributes.
-      included_hook do |_, backend_class|
-        backend_class.include(BackendMethods) if options[:presence]
-      end
-
       module BackendMethods
         # @!group Backend Accessors
         # @!macro backend_reader
         # @option options [Boolean] presence
         #   *false* to disable presence filter.
-        def read(locale, **options)
-          options.delete(:presence) == false ? super : Presence[super]
+        def read(locale, **kwargs)
+          return super unless options[:presence]
+          kwargs.delete(:presence) == false ? super : Presence[super]
         end
 
         # @!macro backend_writer
         # @option options [Boolean] presence
         #   *false* to disable presence filter.
-        def write(locale, value, **options)
-          if options.delete(:presence) == false
+        def write(locale, value, **kwargs)
+          return super unless options[:presence]
+          if kwargs.delete(:presence) == false
             super
           else
-            super(locale, Presence[value], **options)
+            super(locale, Presence[value], **kwargs)
           end
         end
         # @!endgroup

lib/mobility/plugins/sequel/column_fallback.rb

@@ -13,11 +13,6 @@ module ColumnFallback
 
         requires :column_fallback, include: false
 
-        included_hook do |_, backend_class|
-          backend_class.include BackendInstanceMethods
-          backend_class.extend BackendClassMethods
-        end
-
         def self.use_column_fallback?(options, locale)
           case column_fallback = options[:column_fallback]
           when TrueClass
@@ -31,7 +26,7 @@ def self.use_column_fallback?(options, locale)
           end
         end
 
-        module BackendInstanceMethods
+        module BackendMethods
           def read(locale, **)
             if ColumnFallback.use_column_fallback?(options, locale)
               model[attribute.to_sym]