Change `PredicateBuilder` handler methods to instance methods

This will allow us to pass the predicate builder into the constructor of
these handlers. The procs had to be changed to objects, because the
`PredicateBuilder` needs to be marshalable. If we ever decide to make
`register_handler` part of the public API, we should come up with a
better solution which allows procs.

/cc @mrgilman

[Sean Griffin & Melanie Gilman]

activerecord/lib/active_record/relation/predicate_builder.rb

 module ActiveRecord
   class PredicateBuilder # :nodoc:
-    @handlers = []
-
-    autoload :RelationHandler, 'active_record/relation/predicate_builder/relation_handler'
-    autoload :ArrayHandler, 'active_record/relation/predicate_builder/array_handler'
+    require 'active_record/relation/predicate_builder/array_handler'
+    require 'active_record/relation/predicate_builder/base_handler'
+    require 'active_record/relation/predicate_builder/basic_object_handler'
+    require 'active_record/relation/predicate_builder/class_handler'
+    require 'active_record/relation/predicate_builder/range_handler'
+    require 'active_record/relation/predicate_builder/relation_handler'
 
     def initialize(klass, table)
       @klass = klass
       @table = table
+      @handlers = []
+
+      register_handler(BasicObject, BasicObjectHandler.new)
+      register_handler(Class, ClassHandler.new)
+      register_handler(Base, BaseHandler.new)
+      register_handler(Range, RangeHandler.new)
+      register_handler(Relation, RelationHandler.new)
+      register_handler(Array, ArrayHandler.new)
     end
 
     def resolve_column_aliases(hash)
@@ -35,13 +45,13 @@ def expand(column, value)
       # PriceEstimate.where(estimate_of: treasure)
       if klass && reflection = klass._reflect_on_association(column)
         if reflection.polymorphic? && base_class = polymorphic_base_class_from_value(value)
-          queries << self.class.build(table[reflection.foreign_type], base_class.name)
+          queries << build(table[reflection.foreign_type], base_class.name)
         end
 
         column = reflection.foreign_key
       end
 
-      queries << self.class.build(table[column], value)
+      queries << build(table[column], value)
       queries
     end
 
@@ -79,33 +89,10 @@ def self.references(attributes)
     #       )
     #     end
     #     ActiveRecord::PredicateBuilder.register_handler(MyCustomDateRange, handler)
-    def self.register_handler(klass, handler)
+    def register_handler(klass, handler)
       @handlers.unshift([klass, handler])
     end
 
-    register_handler(BasicObject, ->(attribute, value) { attribute.eq(value) })
-    register_handler(Class, ->(attribute, value) { deprecate_class_handler; attribute.eq(value.name) })
-    register_handler(Base, ->(attribute, value) { attribute.eq(value.id) })
-    register_handler(Range, ->(attribute, value) { attribute.between(value) })
-    register_handler(Relation, RelationHandler.new)
-    register_handler(Array, ArrayHandler.new)
-
-    def self.build(attribute, value)
-      handler_for(value).call(attribute, value)
-    end
-
-    def self.handler_for(object)
-      @handlers.detect { |klass, _| klass === object }.last
-    end
-    private_class_method :handler_for
-
-    def self.deprecate_class_handler
-      ActiveSupport::Deprecation.warn(<<-MSG.squish)
-        Passing a class as a value in an Active Record query is deprecated and
-        will be removed. Pass a string instead.
-      MSG
-    end
-
     protected
 
     attr_reader :klass, :table
@@ -141,5 +128,13 @@ def convert_dot_notation_to_hash(attributes)
 
       attributes
     end
+
+    def build(attribute, value)
+      handler_for(value).call(attribute, value)
+    end
+
+    def handler_for(object)
+      @handlers.detect { |klass, _| klass === object }.last
+    end
   end
 end

activerecord/lib/active_record/relation/predicate_builder/base_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class BaseHandler # :nodoc:
+      def call(attribute, value)
+        attribute.eq(value.id)
+      end
+    end
+  end
+end

activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class BasicObjectHandler # :nodoc:
+      def call(attribute, value)
+        attribute.eq(value)
+      end
+    end
+  end
+end

activerecord/lib/active_record/relation/predicate_builder/class_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class ClassHandler # :nodoc:
+      def call(attribute, value)
+        print_deprecation_warning
+        attribute.eq(value.name)
+      end
+
+      private
+
+      def print_deprecation_warning
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          Passing a class as a value in an Active Record query is deprecated and
+          will be removed. Pass a string instead.
+        MSG
+      end
+    end
+  end
+end

activerecord/lib/active_record/relation/predicate_builder/range_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class RangeHandler # :nodoc:
+      def call(attribute, value)
+        attribute.between(value)
+      end
+    end
+  end
+end

activerecord/test/cases/relation/predicate_builder_test.rb

@@ -4,11 +4,13 @@
 module ActiveRecord
   class PredicateBuilderTest < ActiveRecord::TestCase
     def test_registering_new_handlers
-      PredicateBuilder.register_handler(Regexp, proc do |column, value|
+      Topic.predicate_builder.register_handler(Regexp, proc do |column, value|
         Arel::Nodes::InfixOperation.new('~', column, Arel.sql(value.source))
       end)
 
       assert_match %r{["`]topics["`].["`]title["`] ~ rails}i, Topic.where(title: /rails/).to_sql
+    ensure
+      Topic.reset_column_information
     end
   end
 end