Merge pull request #9474 from HonoreDB/master

More helpful error message when instantiating an abstract class

Conflicts:
	activerecord/CHANGELOG.md

3 files changed, 21 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index a7b5ba9f3e..4c594cc19b 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Throw `NotImplementedError` when trying to instantiate `ActiveRecord::Base` or an abstract class.
+
+    *Aaron Weiner*
+
 *   Warn when `rake db:structure:dump` with a mysl database and
     `mysqldump` is not in the PATH or fails.
     Fixes #9518.
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index e630897a4b..13a8352f13 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -15,6 +15,9 @@ module ActiveRecord
       # and if the inheritance column is attr accessible, it initializes an
       # instance of the given subclass instead of the base class
       def new(*args, &block)
+        if abstract_class? || self == Base
+          raise NotImplementedError, "#{self} is an abstract class and can not be instantiated."
+        end
         if (attrs = args.first).is_a?(Hash)
           if subclass = subclass_from_attrs(attrs)
             return subclass.new(*args, &block)
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index af1845c937..8e6e462404 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -307,6 +307,20 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal("last_read", ex.errors[0].attribute)
   end
 
+  def test_initialize_abstract_class
+    e = assert_raises(NotImplementedError) do
+      FirstAbstractClass.new
+    end
+    assert_equal("FirstAbstractClass is an abstract class and can not be instantiated.", e.message)
+  end
+
+  def test_initialize_base
+    e = assert_raises(NotImplementedError) do
+      ActiveRecord::Base.new
+    end
+    assert_equal("ActiveRecord::Base is an abstract class and can not be instantiated.", e.message)
+  end
+
   def test_create_after_initialize_without_block
     cb = CustomBulb.create(:name => 'Dude')
     assert_equal('Dude', cb.name)