Modified default_scope to merge with any pre-existing default_scope

and added AR::Base::clear_default_scope

- clear_default_scope provides users who rely on the old behaviour
  of each call to default_scope overwriting any previous default
  scopes an opportunity to maintain that behaviour.

[#4583 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

2 files changed, 34 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 650a91b385..e7319ce8b9 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1190,7 +1190,11 @@ module ActiveRecord #:nodoc:
         #     default_scope order('last_name, first_name')
         #   end
         def default_scope(options = {})
-          self.default_scoping << construct_finder_arel(options)
+          self.default_scoping << construct_finder_arel(options, default_scoping.pop)
+        end
+
+        def clear_default_scope
+          self.default_scoping.clear
         end
 
         def scoped_methods #:nodoc:
diff --git a/activerecord/test/cases/method_scoping_test.rb b/activerecord/test/cases/method_scoping_test.rb
index a3b496a0e6..3a6354ec6d 100644
--- a/activerecord/test/cases/method_scoping_test.rb
+++ b/activerecord/test/cases/method_scoping_test.rb
@@ -587,6 +587,18 @@ class HasAndBelongsToManyScopingTest< ActiveRecord::TestCase
   end
 end
 
+class ClearDefaultScopeTest < ActiveRecord::TestCase
+  fixtures :developers
+
+  def test_should_clear_default_scope
+    klass = Class.new(DeveloperCalledDavid)
+    klass.__send__ :clear_default_scope
+    expected = Developer.all.collect { |dev| dev.name }
+    actual = klass.all.collect { |dev| dev.name }
+    assert_equal expected, actual
+  end
+end
+
 class DefaultScopingTest < ActiveRecord::TestCase
   fixtures :developers, :posts
 
@@ -615,15 +627,30 @@ class DefaultScopingTest < ActiveRecord::TestCase
   def test_default_scoping_with_inheritance
     # Inherit a class having a default scope and define a new default scope
     klass = Class.new(DeveloperOrderedBySalary)
-    klass.send :default_scope, {}
+    klass.send :default_scope, :limit => 1 
 
     # Scopes added on children should append to parent scope
-    assert klass.scoped.order_values.blank?
+    assert_equal 1,               klass.scoped.limit_value
+    assert_equal ['salary DESC'], klass.scoped.order_values
 
     # Parent should still have the original scope
+    assert_equal nil,             DeveloperOrderedBySalary.scoped.limit_value
     assert_equal ['salary DESC'], DeveloperOrderedBySalary.scoped.order_values
   end
 
+  def test_default_scope_called_twice_merges_conditions
+    Developer.destroy_all
+    Developer.create!(:name => "David", :salary => 80000)
+    Developer.create!(:name => "David", :salary => 100000)
+    Developer.create!(:name => "Brian", :salary => 100000)
+
+    klass = Class.new(Developer)
+    klass.__send__ :default_scope, :conditions => { :name => "David" }
+    klass.__send__ :default_scope, :conditions => { :salary => 100000 }
+    assert_equal 1,       klass.count
+    assert_equal "David", klass.first.name
+    assert_equal 100000,  klass.first.salary
+  end
   def test_method_scope
     expected = Developer.find(:all, :order => 'name DESC').collect { |dev| dev.salary }
     received = DeveloperOrderedBySalary.all_ordered_by_name.collect { |dev| dev.salary }