supporting arel AST nodes when building join statements

activerecord/lib/active_record/associations/through_association_scope.rb

@@ -55,33 +55,35 @@ def construct_select(custom_select = nil)
       end
 
       def construct_joins(custom_joins = nil)
-        polymorphic_join = nil
+        right = @reflection.through_reflection.klass.arel_table
+        left  = @reflection.klass.arel_table
+
+        conditions = []
+
         if @reflection.source_reflection.macro == :belongs_to
           reflection_primary_key = @reflection.klass.primary_key
           source_primary_key     = @reflection.source_reflection.primary_key_name
           if @reflection.options[:source_type]
-            polymorphic_join = "AND %s.%s = %s" % [
-              @reflection.through_reflection.quoted_table_name, "#{@reflection.source_reflection.options[:foreign_type]}",
-              @owner.class.quote_value(@reflection.options[:source_type])
-            ]
+            column = @reflection.source_reflection.options[:foreign_type]
+            conditions <<
+              right[column].eq(@reflection.options[:source_type])
           end
         else
           reflection_primary_key = @reflection.source_reflection.primary_key_name
           source_primary_key     = @reflection.through_reflection.klass.primary_key
           if @reflection.source_reflection.options[:as]
-            polymorphic_join = "AND %s.%s = %s" % [
-              @reflection.quoted_table_name, "#{@reflection.source_reflection.options[:as]}_type",
-              @owner.class.quote_value(@reflection.through_reflection.klass.name)
-            ]
+            column = "#{@reflection.source_reflection.options[:as]}_type"
+            conditions <<
+              left[column].eq(@reflection.through_reflection.klass.name)
           end
         end
 
-        "INNER JOIN %s ON %s.%s = %s.%s %s #{@reflection.options[:joins]} #{custom_joins}" % [
-          @reflection.through_reflection.quoted_table_name,
-          @reflection.quoted_table_name, reflection_primary_key,
-          @reflection.through_reflection.quoted_table_name, source_primary_key,
-          polymorphic_join
-        ]
+        conditions <<
+          left[reflection_primary_key].eq(right[source_primary_key])
+
+        right.create_join(
+          right,
+          right.create_on(right.create_and(conditions)))
       end
 
       # Construct attributes for associate pointing to owner.

activerecord/lib/active_record/relation/query_methods.rb

@@ -247,6 +247,8 @@ def build_joins(manager, joins)
           'association_join'
         when ActiveRecord::Associations::ClassMethods::JoinDependency::JoinAssociation
           'stashed_join'
+        when Arel::Nodes::Join
+          'join_node'
         else
           raise 'unknown class: %s' % join.class.name
         end
@@ -254,12 +256,22 @@ def build_joins(manager, joins)
 
       association_joins         = buckets['association_join'] || []
       stashed_association_joins = buckets['stashed_join'] || []
+      join_nodes                = buckets['join_node'] || []
       string_joins              = (buckets['string_join'] || []).map { |x|
         x.strip
       }.uniq
+
       join_list = custom_join_ast(manager, string_joins)
 
-      join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(@klass, association_joins, join_list)
+      join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(
+        @klass,
+        association_joins,
+        join_list
+      )
+
+      join_nodes.each do |join|
+        join_dependency.table_aliases[join.left.name.downcase] = 1
+      end
 
       join_dependency.graft(*stashed_association_joins)
 
@@ -270,9 +282,9 @@ def build_joins(manager, joins)
         association.join_to(manager)
       end
 
-      return manager unless join_list
+      manager.join_sources.concat join_nodes
+      manager.join_sources.concat join_list
 
-      join_list.each { |j| manager.from j }
       manager
     end