Lock should be a unary node

lib/arel/nodes.rb

@@ -1,6 +1,5 @@
 # node
 require 'arel/nodes/node'
-require 'arel/nodes/lock'
 require 'arel/nodes/select_statement'
 require 'arel/nodes/select_core'
 require 'arel/nodes/insert_statement'

lib/arel/nodes/lock.rb

@@ -1,10 +0,0 @@
-module Arel
-  module Nodes
-    class Lock < Arel::Nodes::Node
-      attr_reader :locking
-      def initialize locking = true
-        @locking = locking
-      end
-    end
-  end
-end

lib/arel/nodes/unary.rb

@@ -18,6 +18,7 @@ module Arel
       Offset
       On
       Top
+      Lock
     }.each do |name|
       const_set(name, Class.new(Unary))
     end

lib/arel/visitors/mysql.rb

@@ -3,8 +3,8 @@ module Arel
     class MySQL < Arel::Visitors::ToSql
       private
       def visit_Arel_Nodes_Lock o
-        if o.locking.is_a?(String)
-          o.locking
+        if o.expr.is_a?(String)
+          o.expr
         else
           "FOR UPDATE"
         end

lib/arel/visitors/postgresql.rb

@@ -3,8 +3,8 @@ module Arel
     class PostgreSQL < Arel::Visitors::ToSql
       private
       def visit_Arel_Nodes_Lock o
-        if o.locking.is_a?(String)
-          o.locking
+        if o.expr.is_a?(String)
+          o.expr
         else
           "FOR UPDATE"
         end

test/visitors/test_depth_first.rb

@@ -63,7 +63,7 @@ module Arel
       end
 
       def test_lock
-        lock = Nodes::Lock.new
+        lock = Nodes::Lock.new true
         @visitor.accept lock
         assert_equal [lock], @collector.calls
       end

test/visitors/test_mysql.rb

@@ -31,7 +31,7 @@ module Arel
 
       describe 'locking' do
         it 'defaults to FOR UPDATE when locking' do
-          node = Nodes::Lock.new
+          node = Nodes::Lock.new true
           @visitor.accept(node).must_be_like "FOR UPDATE"
         end
 

test/visitors/test_postgres.rb

@@ -9,7 +9,7 @@ module Arel
 
       describe 'locking' do
         it 'defaults to FOR UPDATE' do
-          @visitor.accept(Nodes::Lock.new).must_be_like %{
+          @visitor.accept(Nodes::Lock.new(true)).must_be_like %{
             FOR UPDATE
           }
         end