Add Relation#create_with to explictily specify create scope

activerecord/lib/active_record/relation.rb

@@ -6,7 +6,7 @@ module ActiveRecord
 
     attr_reader :relation, :klass
     attr_writer :readonly, :table
-    attr_accessor :preload_associations, :eager_load_associations, :includes_associations
+    attr_accessor :preload_associations, :eager_load_associations, :includes_associations, :create_with_attributes
 
     def initialize(klass, relation)
       @klass, @relation = klass, relation
@@ -124,7 +124,7 @@ module ActiveRecord
     end
 
     def reset
-      @first = @last = @create_scope = @to_sql = @order_clause = nil
+      @first = @last = @to_sql = @order_clause = @scope_for_create = nil
       @records = []
       self
     end
@@ -163,13 +163,15 @@ module ActiveRecord
     end
 
     def with_create_scope
-      @klass.send(:with_scope, :create => create_scope) { yield }
+      @klass.send(:with_scope, :create => scope_for_create) { yield }
     end
 
-    def create_scope
-      @create_scope ||= wheres.inject({}) do |hash, where|
-        hash[where.operand1.name] = where.operand2.value if where.is_a?(Arel::Predicates::Equality)
-        hash
+    def scope_for_create
+      @scope_for_create ||= begin
+        @create_with_attributes || wheres.inject({}) do |hash, where|
+          hash[where.operand1.name] = where.operand2.value if where.is_a?(Arel::Predicates::Equality)
+          hash
+        end
       end
     end
 

activerecord/lib/active_record/relation/query_methods.rb

@@ -17,6 +17,10 @@ module ActiveRecord
       spawn.tap {|r| r.readonly = status }
     end
 
+    def create_with(attributes = {})
+      spawn.tap {|r| r.create_with_attributes = attributes }
+    end
+
     def select(selects)
       if selects.present?
         relation = spawn(@relation.project(selects))

activerecord/lib/active_record/relation/spawn_methods.rb

@@ -6,6 +6,7 @@ module ActiveRecord
       relation.preload_associations = @preload_associations
       relation.eager_load_associations = @eager_load_associations
       relation.includes_associations = @includes_associations
+      relation.create_with_attributes = @create_with_attributes
       relation.table = table
       relation
     end
@@ -32,6 +33,14 @@ module ActiveRecord
       merged_order = relation_order.present? ? relation_order : order_clause
       merged_relation = merged_relation.order(merged_order)
 
+      merged_relation.create_with_attributes = @create_with_attributes
+
+      if @create_with_attributes && r.create_with_attributes
+        merged_relation.create_with_attributes = @create_with_attributes.merge(r.create_with_attributes)
+      else
+        merged_relation.create_with_attributes = r.create_with_attributes || @create_with_attributes
+      end
+
       merged_wheres = @relation.wheres
 
       r.wheres.each do |w|
@@ -56,6 +65,7 @@ module ActiveRecord
       end
 
       result.readonly = self.readonly unless skips.include?(:readonly)
+      result.create_with_attributes = @create_with_attributes unless skips.include?(:create_with)
 
       result = result.joins(@relation.joins(@relation)) unless skips.include?(:joins)
       result = result.group(@relation.groupings) unless skips.include?(:group)

activerecord/test/cases/relations_test.rb

@@ -545,6 +545,14 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal 'hen', hen.name
   end
 
+  def test_explicit_create_scope
+    hens = Bird.where(:name => 'hen')
+    assert_equal 'hen', hens.new.name
+
+    hens = hens.create_with(:name => 'cock')
+    assert_equal 'cock', hens.new.name
+  end
+
   def test_except
     relation = Post.where(:author_id => 1).order('id ASC').limit(1)
     assert_equal [posts(:welcome)], relation.all