JoinDependency is always created with an AST now

activerecord/lib/active_record/associations/class_methods/join_dependency.rb

@@ -49,10 +49,16 @@ module ActiveRecord
 
           return count_aliases_from_string(@table_joins.downcase, name) if String === @table_joins
 
-          @table_joins.grep(Arel::Table).find_all { |table|
-            table.name.downcase == name
-          }.length + @table_joins.grep(String).map { |s|
-            count_aliases_from_string(s, name)
+          @table_joins.grep(Arel::Nodes::Join).map { |join|
+            right = join.right
+            case right
+            when Arel::Table
+              right.name.downcase == name ? 1 : 0
+            when String
+              count_aliases_from_string(right.downcase, name)
+            else
+              0
+            end
           }.sum
         end
 

activerecord/lib/active_record/relation/query_methods.rb

@@ -185,6 +185,20 @@ module ActiveRecord
       arel.join_sql
     end
 
+    def custom_join_ast(joins)
+      joins = joins.reject { |join| join.blank? }
+
+      return if joins.empty?
+
+      @implicit_readonly = true
+
+      head = table.create_string_join(table, joins.shift)
+
+      joins.inject(head) do |ast, join|
+        ast.right = table.create_string_join(ast.right, join)
+      end
+    end
+
     def build_arel
       arel = table
 
@@ -256,7 +270,7 @@ module ActiveRecord
       non_association_joins = (joins - association_joins - stashed_association_joins)
       custom_joins = custom_join_sql(non_association_joins)
 
-      join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(@klass, association_joins, custom_joins)
+      join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(@klass, association_joins, custom_join_ast(non_association_joins))
 
       join_dependency.graft(*stashed_association_joins)