refactoring join_sql to return nil if there are no sources

2 files changed, 12 insertions, 11 deletions

diff --git a/lib/arel/select_manager.rb b/lib/arel/select_manager.rb
index 77930a6bb1..adbf1316d7 100644
--- a/lib/arel/select_manager.rb
+++ b/lib/arel/select_manager.rb
@@ -128,6 +128,8 @@ module Arel
     end
 
     def join_sql
+      return nil unless @ctx.froms
+
       viz = Visitors::JoinSql.new @engine
       Nodes::SqlLiteral.new viz.accept @ctx
     end
diff --git a/lib/arel/table.rb b/lib/arel/table.rb
index e71d7d392c..171d165bc2 100644
--- a/lib/arel/table.rb
+++ b/lib/arel/table.rb
@@ -49,40 +49,39 @@ module Arel
     end
 
     def join relation, klass = Nodes::InnerJoin
-      return select_manager unless relation
+      return from(self) unless relation
 
-      sm = SelectManager.new(@engine)
       case relation
       when String, Nodes::SqlLiteral
         raise if relation.blank?
-        sm.from Nodes::StringJoin.new(self, relation)
+        from Nodes::StringJoin.new(self, relation)
       else
-        sm.from klass.new(self, relation, nil)
+        from klass.new(self, relation, nil)
       end
     end
 
     def group *columns
-      select_manager.group(*columns)
+      from(self).group(*columns)
     end
 
     def order *expr
-      select_manager.order(*expr)
+      from(self).order(*expr)
     end
 
     def where condition
-      select_manager.where condition
+      from(self).where condition
     end
 
     def project *things
-      select_manager.project(*things)
+      from(self).project(*things)
     end
 
     def take amount
-      select_manager.take amount
+      from(self).take amount
     end
 
     def having expr
-      select_manager.having expr
+      from(self).having expr
     end
 
     def columns
@@ -98,7 +97,7 @@ module Arel
     end
 
     def select_manager
-      SelectManager.new(@engine, self)
+      SelectManager.new(@engine)
     end
 
     private