Scoping of uniqueness validations on multiple attributes

Previously the :scoped_to option on the 'should_require_unique_attributes'
only allowed a single attribute to scope uniqueness.  This adds the ability to
scope to multiple attributes.  This also improves the documentation for the
method.

lib/shoulda/active_record_helpers.rb

@@ -51,25 +51,32 @@ module ThoughtBot # :nodoc:
       # Options:
       # * <tt>:message</tt> - value the test expects to find in <tt>errors.on(:attribute)</tt>.  
       #   Regexp or string.  Default = <tt>/taken/</tt>
+      # * <tt>:scoped_to</tt> - field(s) to scope the uniqueness to.
       #
-      # Example:
+      # Examples:
       #   should_require_unique_attributes :keyword, :username
+      #   should_require_unique_attributes :name, :message => "O NOES! SOMEONE STOELED YER NAME!"
+      #   should_require_unique_attributes :email, :scoped_to => :name
+      #   should_require_unique_attributes :address, :scoped_to => [:first_name, :last_name]
       #
       def should_require_unique_attributes(*attributes)
         message, scope = get_options!(attributes, :message, :scoped_to)
+        scope = [*scope].compact
         message ||= /taken/
         
         klass = model_class
         attributes.each do |attribute|
           attribute = attribute.to_sym
-          should "require unique value for #{attribute}#{" scoped to #{scope}" if scope}" do
+          should "require unique value for #{attribute}#{" scoped to #{scope.join(', ')}" if scope}" do
             assert existing = klass.find(:first), "Can't find first #{klass}"
             object = klass.new
             
             object.send(:"#{attribute}=", existing.send(attribute))
-            if scope
-              assert_respond_to object, :"#{scope}=", "#{klass.name} doesn't seem to have a #{scope} attribute."
-              object.send(:"#{scope}=", existing.send(scope))
+            if !scope.blank?
+              scope.each do |s|
+                assert_respond_to object, :"#{s}=", "#{klass.name} doesn't seem to have a #{s} attribute."
+                object.send(:"#{s}=", existing.send(s))
+              end
             end
             
             assert !object.valid?, "#{klass.name} does not require a unique value for #{attribute}."
@@ -82,13 +89,18 @@ module ThoughtBot # :nodoc:
             # to a value that's already taken.  An alternative implementation
             # could actually find all values for scope and create a unique
             # one.  
-            if scope
+            if !scope.blank?
+              scope.each do |s|
               # Assume the scope is a foreign key if the field is nil
-              object.send(:"#{scope}=", existing.send(scope).nil? ? 1 : existing.send(scope).next)
+                object.send(:"#{s}=", existing.send(s).nil? ? 1 : existing.send(s).next)
+              end
+
               object.errors.clear
               object.valid?
-              assert_does_not_contain(object.errors.on(attribute), message, 
-                                      "after :#{scope} set to #{object.send(scope.to_sym)}")
+              scope.each do |s|
+                assert_does_not_contain(object.errors.on(attribute), message, 
+                                        "after :#{s} set to #{object.send(s.to_sym)}")
+              end
             end
           end
         end

test/fixtures/addresses.yml

@@ -0,0 +1,3 @@
+first:
+  title: Home
+  addressable: first (User)

test/rails_root/app/models/address.rb

@@ -1,3 +1,4 @@
 class Address < ActiveRecord::Base
   belongs_to :addressable, :polymorphic => true
+  validates_uniqueness_of :title, :scope => [:addressable_type, :addressable_id]
 end

test/rails_root/app/models/user.rb

@@ -10,4 +10,5 @@ class User < ActiveRecord::Base
   validates_length_of :email, :in => 1..100
   validates_inclusion_of :age, :in => 1..100
   validates_acceptance_of :eula
+  validates_uniqueness_of :email, :scope => :name
 end

test/rails_root/db/migrate/006_create_addresses.rb

@@ -1,6 +1,7 @@
 class CreateAddresses < ActiveRecord::Migration
   def self.up
     create_table :addresses do |t|
+      t.column :title, :string
       t.column :addressable_id, :integer
       t.column :addressable_type, :string
     end

test/unit/address_test.rb

@@ -3,4 +3,5 @@ require File.dirname(__FILE__) + '/../test_helper'
 class AddressTest < Test::Unit::TestCase
   load_all_fixtures
   should_belong_to :addressable
+  should_require_unique_attributes :title, :scoped_to => [:addressable_id, :addressable_type]
 end

test/unit/user_test.rb

@@ -23,4 +23,5 @@ class UserTest < Test::Unit::TestCase
   should_have_db_column :email, :type => "string", :default => nil,   :precision => nil, :limit    => 255, 
                                 :null => true,     :primary => false, :scale     => nil, :sql_type => 'varchar(255)'
   should_require_acceptance_of :eula
+  should_require_unique_attributes :email, :scoped_to => :name
 end