Replace QueryMethods with nodes and Query plugin

I've left this as one giant commit, because to split it is more work
that it is worth. This change replaces module builders for each backend
with a single plugin which delegates to the methods build_node (which
returns an Arel node) and (optionally) add_translations (which modifies
an AR::Relation) on the backend class.

Backend classes now need only to implement these one or two methods and
querying is supported without any extra work.

lib/mobility/active_record.rb

@@ -12,24 +12,12 @@ module ActiveRecord
 
     def self.included(model_class)
       model_class.class_eval do
-        extend QueryMethod.new(Mobility.query_method)
         unless const_defined?(:UniquenessValidator)
           const_set(:UniquenessValidator,
                     Class.new(::Mobility::ActiveRecord::UniquenessValidator))
         end
         delegate :translated_attribute_names, to: :class
       end
     end
-
-    class QueryMethod < Module
-      def initialize(query_method)
-        module_eval <<-EOM, __FILE__, __LINE__ + 1
-          def #{query_method}
-            all
-          end
-        EOM
-      end
-    end
-    private_constant :QueryMethod
   end
 end

lib/mobility/backends/active_record.rb

@@ -1,19 +1,31 @@
 module Mobility
   module Backends
     module ActiveRecord
-      def setup_query_methods(query_methods)
-        setup do |attributes, options|
-          extend(Module.new do
-            define_method ::Mobility.query_method do
-              super().extending(query_methods.new(attributes, options))
-            end
-          end)
-        end
-      end
-
       def self.included(backend_class)
         backend_class.include(Backend)
-        backend_class.extend(self)
+        backend_class.extend(ClassMethods)
+      end
+
+      module ClassMethods
+        # @param [String] _attr Attribute name
+        # @param [Symbol] _locale Locale
+        def build_node(_attr, _locale)
+          raise NotImplementedError
+        end
+
+        # @param [ActiveRecord::Relation] relation Relation to scope
+        # @param [Symbol] locale Locale
+        # @option [Boolean] invert
+        # @return [ActiveRecord::Relation] Relation with scope added
+        def add_translations(relation, _opts, _locale, invert: false)
+          relation
+        end
+
+        private
+
+        def build_quoted(value)
+          ::Arel::Nodes.build_quoted(value)
+        end
       end
     end
   end

lib/mobility/backends/active_record/column.rb

@@ -34,8 +34,6 @@ class ActiveRecord::Column
       include ActiveRecord
       include Column
 
-      require 'mobility/backends/active_record/column/query_methods'
-
       # @!group Backend Accessors
       # @!macro backend_reader
       def read(locale, _ = {})
@@ -53,7 +51,9 @@ def each_locale
         available_locales.each { |l| yield(l) if present?(l) }
       end
 
-      setup_query_methods(QueryMethods)
+      def self.build_node(attr, locale)
+        model_class.arel_table[Column.column_name_for(attr, locale)]
+      end
 
       private
 

lib/mobility/backends/active_record/container.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 require "mobility/backends/active_record"
+require "mobility/arel/nodes/pg_ops"
 
 module Mobility
   module Backends
@@ -11,9 +12,6 @@ module Backends
     class ActiveRecord::Container
       include ActiveRecord
 
-      require 'mobility/backends/active_record/container/json_query_methods'
-      require 'mobility/backends/active_record/container/jsonb_query_methods'
-
       # @!method column_name
       #   Returns name of json or jsonb column used to store translations
       #   @return [Symbol] (:translations) Name of translations column
@@ -59,16 +57,28 @@ def self.configure(options)
       end
       # @!endgroup
 
+      # @param [String] attr Attribute name
+      # @param [Symbol] locale Locale
+      def self.build_node(attr, locale)
+        column        = model_class.arel_table[column_name]
+        quoted_locale = build_quoted(locale)
+        quoted_attr   = build_quoted(attr)
+        case column_type
+        when :json
+          Arel::Nodes::Json.new(Arel::Nodes::JsonDashArrow.new(column, quoted_locale), quoted_attr)
+        when :jsonb
+          Arel::Nodes::Jsonb.new(Arel::Nodes::Jsonb.new(column, quoted_locale), quoted_attr)
+        end
+      end
+
       # @!macro backend_iterator
       def each_locale
         model[column_name].each do |l, v|
           yield l.to_sym if v.present?
         end
       end
 
-      backend_class = self
-
-      setup do |attributes, options|
+      setup do |_attributes, options|
         store options[:column_name], coder: Coder
 
         # Fix for duping depth-2 jsonb column in AR < 5.0
@@ -87,13 +97,6 @@ def initialize_dup(source)
             include const_set(module_name, dupable)
           end
         end
-
-        query_methods = backend_class.const_get("#{options[:column_type].capitalize}QueryMethods")
-        extend(Module.new do
-          define_method ::Mobility.query_method do
-            super().extending(query_methods.new(attributes, options))
-          end
-        end)
       end
 
       private

lib/mobility/backends/active_record/hstore.rb

@@ -1,4 +1,5 @@
 require 'mobility/backends/active_record/pg_hash'
+require 'mobility/arel/nodes/pg_ops'
 
 module Mobility
   module Backends
@@ -11,8 +12,6 @@ module Backends
 =end
     module ActiveRecord
       class Hstore < PgHash
-        require 'mobility/backends/active_record/hstore/query_methods'
-
         # @!group Backend Accessors
         # @!macro backend_reader
         # @!method read(locale, options = {})
@@ -23,7 +22,12 @@ def write(locale, value, options = {})
         end
         # @!endgroup
 
-        setup_query_methods(QueryMethods)
+        # @param [String] attr Attribute name
+        # @param [Symbol] locale Locale
+        def self.build_node(attr, locale)
+          column_name = column_affix % attr
+          Arel::Nodes::Hstore.new(model_class.arel_table[column_name], build_quoted(locale))
+        end
       end
     end
   end

lib/mobility/backends/active_record/json.rb

@@ -1,4 +1,5 @@
 require 'mobility/backends/active_record/pg_hash'
+require 'mobility/arel/nodes/pg_ops'
 
 module Mobility
   module Backends
@@ -11,8 +12,6 @@ module Backends
 =end
     module ActiveRecord
       class Json < PgHash
-        require 'mobility/backends/active_record/json/query_methods'
-
         # @!group Backend Accessors
         #
         # @!method read(locale, **options)
@@ -31,7 +30,12 @@ class Json < PgHash
         #   @return [String,Integer,Boolean] Updated value
         # @!endgroup
 
-        setup_query_methods(QueryMethods)
+        # @param [String] attr Attribute name
+        # @param [Symbol] locale Locale
+        def self.build_node(attr, locale)
+          column_name = column_affix % attr
+          Arel::Nodes::Json.new(model_class.arel_table[column_name], build_quoted(locale))
+        end
       end
     end
   end