TreeManager classes deep-copy their statements.

lib/arel/tree_manager.rb

@@ -15,5 +15,10 @@ module Arel
       viz = Visitors::ToSql.new @engine
       viz.accept @head
     end
+
+    def initialize_copy other
+      super
+      @head = @head.clone
+    end
   end
 end

spec/arel/insert_manager_spec.rb

@@ -110,5 +110,16 @@ module Arel
         }
       end
     end
+
+    describe "TreeManager" do
+      subject do
+        table = Table.new(:users)
+        Arel::InsertManager.new(Table.engine).tap do |manager|
+          manager.insert [[table[:id], nil]]
+        end
+      end
+
+      it_should_behave_like "TreeManager"
+    end
   end
 end

spec/arel/select_manager_spec.rb

@@ -166,5 +166,16 @@ module Arel
         manager.to_sql.should be_like 'SELECT "users"."id" FROM "users"'
       end
     end
+
+    describe "TreeManager" do
+      subject do
+        table   = Table.new :users
+        Arel::SelectManager.new(Table.engine).tap do |manager|
+          manager.from(table).project(table['id'])
+        end
+      end
+
+      it_should_behave_like "TreeManager"
+    end
   end
 end

spec/arel/update_manager_spec.rb

@@ -73,5 +73,17 @@ module Arel
         um.where(table[:id].eq(1)).should == um
       end
     end
+
+    describe "TreeManager" do
+      subject do
+        table = Table.new :users
+        Arel::UpdateManager.new(Table.engine).tap do |manager|
+          manager.table table
+          manager.where table[:id].eq(1)
+        end
+      end
+
+      it_should_behave_like "TreeManager"
+    end
   end
 end

spec/spec_helper.rb

@@ -5,6 +5,7 @@ require 'arel'
 
 require 'support/matchers/be_like'
 require 'support/check'
+Dir[File.join(File.dirname(__FILE__),'support/shared/*')].each { |f| require f }
 
 if adapter = ENV['ADAPTER']
   require "support/connections/#{adapter}_connection.rb"

spec/support/shared/tree_manager_shared.rb

@@ -0,0 +1,9 @@
+shared_examples_for "TreeManager" do
+  describe "clone" do
+    it "clones the insert statement" do
+      subject.instance_variable_get("@head").should_receive(:clone).and_return(:foo) # TODO: ick.
+      dolly = subject.clone
+      dolly.instance_variable_get("@head").should == :foo
+    end
+  end
+end