10 files changed, 55 insertions, 28 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 810a2c668d..9cf619f4c2 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Objects intiantiated using a null relationship will now retain the
+    attributes of the where clause.
+
+    Fixes:  #11676, #11675, #11376
+
+    *Paul Nikitochkin*, *Peter Brown*, *Nthalk*
+
 *   Fixed `ActiveRecord::Associations::CollectionAssociation#find`
     when using `has_many` association with `:inverse_of` and finding an array of one element,
     it should return an array of one element too.
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 208da2cb77..bf270c1829 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/enumerable'
 require 'mutex_m'
+require 'thread_safe'
 
 module ActiveRecord
   # = Active Record Attribute Methods
@@ -29,23 +30,18 @@ module ActiveRecord
     }
 
     class AttributeMethodCache
-      include Mutex_m
-
       def initialize
-        super
         @module = Module.new
-        @method_cache = {}
+        @method_cache = ThreadSafe::Cache.new
       end
 
       def [](name)
-        synchronize do
-          @method_cache.fetch(name) {
-            safe_name = name.unpack('h*').first
-            temp_method = "__temp__#{safe_name}"
-            ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name
-            @module.module_eval method_body(temp_method, safe_name), __FILE__, __LINE__
-            @method_cache[name] = @module.instance_method temp_method
-          }
+        @method_cache.compute_if_absent(name) do
+          safe_name = name.unpack('h*').first
+          temp_method = "__temp__#{safe_name}"
+          ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name
+          @module.module_eval method_body(temp_method, safe_name), __FILE__, __LINE__
+          @module.instance_method temp_method
         end
       end
 
diff --git a/activerecord/lib/active_record/log_subscriber.rb b/activerecord/lib/active_record/log_subscriber.rb
index 0358a36b14..927fbab8f0 100644
--- a/activerecord/lib/active_record/log_subscriber.rb
+++ b/activerecord/lib/active_record/log_subscriber.rb
@@ -17,7 +17,7 @@ module ActiveRecord
 
     def initialize
       super
-      @odd_or_even = false
+      @odd = false
     end
 
     def render_bind(column, value)
@@ -60,17 +60,8 @@ module ActiveRecord
       debug "  #{name}  #{sql}#{binds}"
     end
 
-    def identity(event)
-      return unless logger.debug?
-
-      name = color(event.payload[:name], odd? ? CYAN : MAGENTA, true)
-      line = odd? ? color(event.payload[:line], nil, true) : event.payload[:line]
-
-      debug "  #{name}  #{line}"
-    end
-
     def odd?
-      @odd_or_even = !@odd_or_even
+      @odd = !@odd
     end
 
     def logger
diff --git a/activerecord/lib/active_record/null_relation.rb b/activerecord/lib/active_record/null_relation.rb
index d166f0dd66..716020e7e7 100644
--- a/activerecord/lib/active_record/null_relation.rb
+++ b/activerecord/lib/active_record/null_relation.rb
@@ -42,10 +42,6 @@ module ActiveRecord
       ""
     end
 
-    def where_values_hash
-      {}
-    end
-
     def count(*)
       0
     end
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index fd8496442e..49b01909c6 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -34,7 +34,7 @@ module ActiveRecord
     # between id 0 and 10,000 and worker 2 handle from 10,000 and beyond
     # (by setting the +:start+ option on that worker).
     #
-    #   # Let's process for a batch of 2000 records, skiping the first 2000 rows
+    #   # Let's process for a batch of 2000 records, skipping the first 2000 rows
     #   Person.find_each(start: 2000, batch_size: 2000) do |person|
     #     person.party_all_night!
     #   end
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 064e31f634..caa916346a 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -80,6 +80,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal 'exotic', bulb.name
   end
 
+  def test_build_from_association_should_respect_scope
+    author = Author.new
+
+    post = author.thinking_posts.build
+    assert_equal 'So I was thinking', post.title
+  end
+
   def test_create_from_association_with_nil_values_should_work
     car = Car.create(:name => 'honda')
 
@@ -1629,6 +1636,22 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal car.id, bulb.attributes_after_initialize['car_id']
   end
 
+  def test_attributes_are_set_when_initialized_from_has_many_null_relationship
+    car  = Car.new name: 'honda'
+    bulb = car.bulbs.where(name: 'headlight').first_or_initialize
+    assert_equal 'headlight', bulb.name
+  end
+
+  def test_attributes_are_set_when_initialized_from_polymorphic_has_many_null_relationship
+    post    = Post.new title: 'title', body: 'bar'
+    tag     = Tag.create!(name: 'foo')
+
+    tagging = post.taggings.where(tag: tag).first_or_initialize
+
+    assert_equal tag.id, tagging.tag_id
+    assert_equal 'Post', tagging.taggable_type
+  end
+
   def test_replace
     car = Car.create(:name => 'honda')
     bulb1 = car.bulbs.create
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index c0e80c5fe9..5299e4e17e 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -37,6 +37,13 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     Reader.create :person_id => 0, :post_id => 0
   end
 
+  def test_preload_sti_rhs_class
+    developers = Developer.includes(:firms).all.to_a
+    assert_no_queries do
+      developers.each { |d| d.firms }
+    end
+  end
+
   def test_preload_sti_middle_relation
     club = Club.create!(name: 'Aaron cool banana club')
     member1 = Member.create!(name: 'Aaron')
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 88a12c61df..9e5ffa0cce 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -300,6 +300,10 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal({}, Developer.none.where_values_hash)
   end
 
+  def test_null_relation_where_values_hash
+    assert_equal({ 'salary' => 100_000 }, Developer.none.where(salary: 100_000).where_values_hash)
+  end
+
   def test_joins_with_nil_argument
     assert_nothing_raised { DependentFirm.joins(nil).first }
   end
diff --git a/activerecord/test/models/contract.rb b/activerecord/test/models/contract.rb
index 2cf5aa7a85..cdf7b267b5 100644
--- a/activerecord/test/models/contract.rb
+++ b/activerecord/test/models/contract.rb
@@ -1,6 +1,7 @@
 class Contract < ActiveRecord::Base
   belongs_to :company
   belongs_to :developer
+  belongs_to :firm, :foreign_key => 'company_id'
 
   before_save :hi
   after_save :bye
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index c8e2be580e..a26de55758 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -38,6 +38,8 @@ class Developer < ActiveRecord::Base
   has_and_belongs_to_many :special_projects, :join_table => 'developers_projects', :association_foreign_key => 'project_id'
 
   has_many :audit_logs
+  has_many :contracts
+  has_many :firms, :through => :contracts, :source => :firm
 
   scope :jamises, -> { where(:name => 'Jamis') }