AMo #key is now #to_key and CI is probably happy

Obviously #key is a too common name to be included
in the AMo interface, #to_key fits better and also
relates nicely to #to_param. Thx wycats, koz and
josevalim for the suggestion.

AR's #to_key implementation now takes customized
primary keys into account and there's a testcase
for that too.

The #to_param AMo lint makes no assumptions on how
the method behaves in the presence of composite
primary keys. It leaves the decision wether to
provide a default, or to raise and thus signal to
the user that implementing this method will need
his special attention, up to the implementers. All
AMo cares about is that #to_param is implemented
and returns nil in case of a new_record?.

The default CompliantObject used in lint_test
provides a naive default implementation that just
joins all key attributes with '-'.

The #to_key default implementation in lint_test's
CompliantObject now returns [id] instead of [1].
This was previously causing the (wrong) tests I
added for AR's #to_key implementation to pass. The
#to_key tests added with this patch should be
better.

The CI failure was caused by my lack of knowledge
about the test:isolated task. The tests for the
record_identifier code in action_controller are
using fake non AR models and I forgot to stub the
#to_key method over there. This issue didn't come
up when running the test task, only test:isolated
revealed it. This patch fixes that.

All tests pass isolated or not, well, apart from
one previously unpended test in action_controller
that is unrelated to my patch.

2 files changed, 15 insertions, 8 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index ba64b8ee2f..8549414a12 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -45,10 +45,12 @@ module ActiveRecord
         # Returns this record's primary key value wrapped in an Array
         # or nil if the record is a new_record?
         # This is done to comply with the AMo interface that expects
-        # every AMo compliant object to respond_to?(:key) and return
+        # every AMo compliant object to respond_to?(:to_key) and return
         # an Enumerable object from that call, or nil if new_record?
-        def key
-          new_record? ? nil : [ self.id ]
+        # This method also takes custom primary keys specified via
+        # the +set_primary_key+ into account.
+        def to_key
+          new_record? ? nil : [ self.send(self.class.primary_key) ]
         end
 
       end
diff --git a/activerecord/test/cases/pk_test.rb b/activerecord/test/cases/pk_test.rb
index 2502c136cc..5bba1d5625 100644
--- a/activerecord/test/cases/pk_test.rb
+++ b/activerecord/test/cases/pk_test.rb
@@ -9,13 +9,18 @@ require 'models/mixed_case_monkey'
 class PrimaryKeysTest < ActiveRecord::TestCase
   fixtures :topics, :subscribers, :movies, :mixed_case_monkeys
 
-  def test_key
-    # test new record
+  def test_to_key_with_default_primary_key
     topic = Topic.new
-    assert topic.key.nil?
-    # test existing record
+    assert topic.to_key.nil?
     topic = Topic.find(1)
-    assert_equal topic.key, [1]
+    assert_equal topic.to_key, [1]
+  end
+
+  def test_to_key_with_customized_primary_key
+    keyboard = Keyboard.new
+    assert keyboard.to_key.nil?
+    keyboard.save
+    assert_equal keyboard.to_key, [keyboard.id]
   end
 
   def test_integer_key