Raise an exception when model without primary key calls .find_with_ids

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Raise an exception when model without primary key calls `.find_with_ids`.
+
+    *Shimpei Makimoto*
+
 *   Make `Relation#empty?` use `exists?` instead of `count`.
 
     *Szymon Nowak*

activerecord/lib/active_record/relation/finder_methods.rb

@@ -297,6 +297,8 @@ def using_limitable_reflections?(reflections)
     protected
 
     def find_with_ids(*ids)
+      raise UnknownPrimaryKey.new(@klass) if primary_key.nil?
+
       expects_array = ids.first.kind_of?(Array)
       return ids.first if expects_array && ids.first.empty?
 

activerecord/test/cases/finder_test.rb

@@ -11,6 +11,7 @@
 require 'models/developer'
 require 'models/customer'
 require 'models/toy'
+require 'models/matey'
 
 class FinderTest < ActiveRecord::TestCase
   fixtures :companies, :topics, :entrants, :developers, :developers_projects, :posts, :comments, :accounts, :authors, :customers, :categories, :categorizations
@@ -860,6 +861,12 @@ def test_find_one_message_with_custom_primary_key
     Toy.reset_primary_key
   end
 
+  def test_find_without_primary_key
+    assert_raises(ActiveRecord::UnknownPrimaryKey) do
+      Matey.find(1)
+    end
+  end
+
   def test_finder_with_offset_string
     assert_nothing_raised(ActiveRecord::StatementInvalid) { Topic.all.merge!(:offset => "3").to_a }
   end