Use composite primary_key value as a fallback for query_constraints_list

Given a model with a composite primary key, the `query_constraints_list`
should equal the `primary_key` value to enable capabilities managed by
`query_constraints_list` such as `destroy`, `update`, `delete` and others.

Author: nvasilevski

activerecord/lib/active_record/persistence.rb

@@ -493,7 +493,7 @@ def query_constraints(*columns_list)
 
       def query_constraints_list # :nodoc:
         @query_constraints_list ||= if base_class? || primary_key != base_class.primary_key
-          @_query_constraints_list
+          primary_key.is_a?(Array) ? primary_key : @_query_constraints_list
         else
           base_class.query_constraints_list
         end

activerecord/test/cases/persistence_test.rb

@@ -21,6 +21,7 @@
 require "models/ship"
 require "models/admin"
 require "models/admin/user"
+require "models/cpk"
 
 class PersistenceTest < ActiveRecord::TestCase
   fixtures :topics, :companies, :developers, :accounts, :minimalistics, :authors, :author_addresses,
@@ -1448,25 +1449,14 @@ def test_query_constraints_list_is_nil_if_primary_key_is_nil
     assert_nil klass.query_constraints_list
   end
 
-  def test_query_constraints_uses_primary_key_by_default
-    post = posts(:welcome)
-    assert_uses_query_constraints_on_reload(post, "id")
+  def test_query_constraints_list_is_nil_for_non_cpk_model
+    assert_nil Post.query_constraints_list
+    assert_nil Dashboard.query_constraints_list
   end
 
-  def test_query_constraints_uses_manually_configured_primary_key
-    dashboard = dashboards(:cool_first)
-    assert_uses_query_constraints_on_reload(dashboard, "dashboard_id")
-  end
-
-  def test_child_overriden_primary_key_is_used_as_query_constraint
-    topic = topics(:first)
-    assert_uses_query_constraints_on_reload(topic, "id")
-
-    title_pk_topic = topic.becomes(TitlePrimaryKeyTopic)
-    title_pk_topic.author_name = "Nikita"
-
-    sql = capture_sql { title_pk_topic.save }.first
-    assert_match(/WHERE .*title/, sql)
+  def test_query_constraints_list_equals_to_composite_primary_key
+    assert_equal(["shop_id", "id"], Cpk::Order.query_constraints_list)
+    assert_equal(["author_id", "number"], Cpk::Book.query_constraints_list)
   end
 
   def test_child_keeps_parents_query_constraints
@@ -1477,6 +1467,10 @@ def test_child_keeps_parents_query_constraints
     assert_uses_query_constraints_on_reload(used_clothing_item, ["clothing_type", "color"])
   end
 
+  def test_child_keeps_parents_query_contraints_derived_from_composite_pk
+    assert_equal(["author_id", "number"], Cpk::BestSeller.query_constraints_list)
+  end
+
   def assert_uses_query_constraints_on_reload(object, columns)
     flunk("columns argument must not be empty") if columns.blank?
 

activerecord/test/models/cpk/book.rb

@@ -5,4 +5,7 @@ class Book < ActiveRecord::Base
     self.table_name = :cpk_books
     self.primary_key = [:author_id, :number]
   end
+
+  class BestSeller < Book
+  end
 end