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.

1 files changed, 12 insertions, 6 deletions

diff --git a/activemodel/lib/active_model/lint.rb b/activemodel/lib/active_model/lint.rb
index c97286e61c..98413ac9fb 100644
--- a/activemodel/lib/active_model/lint.rb
+++ b/activemodel/lib/active_model/lint.rb
@@ -14,22 +14,28 @@ module ActiveModel
   module Lint
     module Tests
 
-      # == Responds to <tt>key</tt>
+      # == Responds to <tt>to_key</tt>
       #
       # Returns an Enumerable of all (primary) key attributes
       # or nil if model.new_record? is true
-      def test_key
-        assert model.respond_to?(:key), "The model should respond to key"
+      def test_to_key
+        assert model.respond_to?(:to_key), "The model should respond to to_key"
         def model.new_record?() true end
-        assert model.key.nil?
+        assert model.to_key.nil?
         def model.new_record?() false end
-        assert model.key.respond_to?(:each)
+        assert model.to_key.respond_to?(:each)
       end
 
       # == Responds to <tt>to_param</tt>
       #
       # Returns a string representing the object's key suitable for use in URLs
-      # or nil if model.new_record? is true
+      # or nil if model.new_record? is true.
+      #
+      # Implementers can decide to either raise an exception or provide a default
+      # in case the record uses a composite primary key. There are no tests for this
+      # behavior in lint because it doesn't make sense to force any of the possible
+      # implementation strategies on the implementer. However, if the resource is
+      # a new_record?, then to_param should always return nil.
       def test_to_param
         assert model.respond_to?(:to_param), "The model should respond to to_param"
         def model.new_record?() true end