8 files changed, 55 insertions, 23 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index f3362f81a3..186c7bf244 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,15 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Fix bug with presence validation of associations. Would incorrectly add duplicated errors 
+    when the association was blank. Bug introduced in 1fab518c6a75dac5773654646eb724a59741bc13.
+
+    *Scott Willson*
+
+*   Fix bug where sum(expression) returns string '0' for no matching records
+    Fixes #7439
+
+    *Tim Macfarlane*
+
 *   PostgreSQL adapter correctly fetches default values when using multiple schemas and domains in a db. Fixes #7914
 
     *Arturo Pie*
@@ -8,7 +18,7 @@
 
     When symbol or hash passed we convert it to Arel::Nodes::Ordering.
     If we pass invalid direction(like name: :DeSc) ActiveRecord::QueryMethods#order will raise an exception
-    
+
         User.order(:name, email: :desc)
         # SELECT "users".* FROM "users" ORDER BY "users"."name" ASC, "users"."email" DESC
 
@@ -283,6 +293,11 @@
 
     *Ari Pollak*
 
+*   Fix AR#dup to nullify the validation errors in the dup'ed object. Previously the original
+    and the dup'ed object shared the same errors.
+
+    * Christian Seiler*
+
 *   Raise `ArgumentError` if list of attributes to change is empty in `update_all`.
 
     *Roman Shatsov*
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 7c43d844d0..a7d2f4bd24 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -343,13 +343,13 @@ module ActiveRecord
 
     def column_for(field)
       field_name = field.respond_to?(:name) ? field.name.to_s : field.to_s.split('.').last
-      @klass.columns.detect { |c| c.name.to_s == field_name }
+      @klass.columns_hash[field_name]
     end
 
     def type_cast_calculated_value(value, column, operation = nil)
       case operation
         when 'count'   then value.to_i
-        when 'sum'     then type_cast_using_column(value || '0', column)
+        when 'sum'     then type_cast_using_column(value || 0, column)
         when 'average' then value.respond_to?(:to_d) ? value.to_d : value
         else type_cast_using_column(value, column)
       end
diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index bf95ccb298..dd08a6f4f5 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -42,6 +42,7 @@ module ActiveRecord
 
     def initialize_dup(other) # :nodoc:
       clear_timestamp_attributes
+      super
     end
 
   private
diff --git a/activerecord/lib/active_record/validations/presence.rb b/activerecord/lib/active_record/validations/presence.rb
index 81a3521d24..6b14c39686 100644
--- a/activerecord/lib/active_record/validations/presence.rb
+++ b/activerecord/lib/active_record/validations/presence.rb
@@ -5,8 +5,10 @@ module ActiveRecord
         super
         attributes.each do |attribute|
           next unless record.class.reflect_on_association(attribute)
-          value = record.send(attribute)
-          if Array(value).all? { |r| r.marked_for_destruction? }
+          associated_records = Array(record.send(attribute))
+
+          # Superclass validates presence. Ensure present records aren't about to be destroyed.
+          if associated_records.present? && associated_records.all? { |r| r.marked_for_destruction? }
             record.errors.add(attribute, :blank, options)
           end
         end
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 6cb6c469d2..abbf2a765e 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -6,6 +6,8 @@ require 'models/edge'
 require 'models/organization'
 require 'models/possession'
 require 'models/topic'
+require 'models/minivan'
+require 'models/speedometer'
 
 Company.has_many :accounts
 
@@ -239,21 +241,12 @@ class CalculationsTest < ActiveRecord::TestCase
   end
 
   def test_should_group_by_association_with_non_numeric_foreign_key
-    ActiveRecord::Base.connection.expects(:select_all).returns([{"count_all" => 1, "firm_id" => "ABC"}])
+    Speedometer.create! id: 'ABC'
+    Minivan.create! id: 'OMG', speedometer_id: 'ABC'
 
-    firm = mock()
-    firm.expects(:id).returns("ABC")
-    firm.expects(:class).returns(Firm)
-    Company.expects(:find).with(["ABC"]).returns([firm])
-
-    column = mock()
-    column.expects(:name).at_least_once.returns(:firm_id)
-    column.expects(:type_cast).with("ABC").returns("ABC")
-    Account.expects(:columns).at_least_once.returns([column])
-
-    c = Account.group(:firm).count(:all)
+    c = Minivan.group(:speedometer).count(:all)
     first_key = c.keys.first
-    assert_equal Firm, first_key.class
+    assert_equal Speedometer, first_key.class
     assert_equal 1, c[first_key]
   end
 
@@ -378,6 +371,10 @@ class CalculationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_sum_expression_returns_zero_when_no_records_to_sum
+    assert_equal 0, Account.where('1 = 2').sum("2 * credit_limit")
+  end
+
   def test_count_with_from_option
     assert_equal Company.count(:all), Company.from('companies').count(:all)
     assert_equal Account.where("credit_limit = 50").count(:all),
diff --git a/activerecord/test/cases/dup_test.rb b/activerecord/test/cases/dup_test.rb
index 71b2b16608..4e2adff344 100644
--- a/activerecord/test/cases/dup_test.rb
+++ b/activerecord/test/cases/dup_test.rb
@@ -107,5 +107,19 @@ module ActiveRecord
       assert Topic.after_initialize_called
     end
 
+    def test_dup_validity_is_independent
+      Topic.validates_presence_of :title
+      topic = Topic.new("title" => "Litterature")
+      topic.valid?
+
+      duped = topic.dup
+      duped.title = nil
+      assert duped.invalid?
+
+      topic.title = nil
+      duped.title = 'Mathematics'
+      assert topic.invalid?
+      assert duped.valid?
+    end
   end
 end
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index 80f46c6b08..5f13124e5b 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -2,13 +2,9 @@ require "cases/helper"
 
 
 class SchemaDumperTest < ActiveRecord::TestCase
-  def initialize(*)
-    super
-    ActiveRecord::SchemaMigration.create_table
-  end
-
   def setup
     super
+    ActiveRecord::SchemaMigration.create_table
     @stream = StringIO.new
   end
 
diff --git a/activerecord/test/cases/validations/presence_validation_test.rb b/activerecord/test/cases/validations/presence_validation_test.rb
index cd9175f454..1de8934406 100644
--- a/activerecord/test/cases/validations/presence_validation_test.rb
+++ b/activerecord/test/cases/validations/presence_validation_test.rb
@@ -18,6 +18,13 @@ class PresenceValidationTest < ActiveRecord::TestCase
     assert b.valid?
   end
 
+  def test_validates_presence_of_has_one
+    Boy.validates_presence_of(:face)
+    b = Boy.new
+    assert b.invalid?, "should not be valid if has_one association missing"
+    assert_equal 1, b.errors[:face].size, "validates_presence_of should only add one error"
+  end
+
   def test_validates_presence_of_has_one_marked_for_destruction
     Boy.validates_presence_of(:face)
     b = Boy.new