Raise error on unknown primary key.

If we don't have a primary key when we ask for it, it's better to fail
fast. Fixes GH #2307.

3 files changed, 18 insertions, 4 deletions

diff --git a/activerecord/test/cases/attribute_methods/read_test.rb b/activerecord/test/cases/attribute_methods/read_test.rb
index e03ed33591..814476ce73 100644
--- a/activerecord/test/cases/attribute_methods/read_test.rb
+++ b/activerecord/test/cases/attribute_methods/read_test.rb
@@ -24,6 +24,10 @@ module ActiveRecord
           def self.primary_key
           end
 
+          def self.primary_key?
+            false
+          end
+
           def self.columns
             column_names.map { FakeColumn.new(name) }
           end
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 12c1cfb30e..77fd1d2fad 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -97,10 +97,6 @@ class BasicsTest < ActiveRecord::TestCase
     assert pk.primary, 'nick should be primary key'
   end
 
-  def test_primary_key_with_no_id
-    assert_nil Edge.primary_key
-  end
-
   unless current_adapter?(:PostgreSQLAdapter,:OracleAdapter,:SQLServerAdapter)
     def test_limit_with_comma
       assert_nothing_raised do
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index 489c7d8310..58badd6266 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -5,6 +5,7 @@ require 'models/subscriber'
 require 'models/movie'
 require 'models/keyboard'
 require 'models/mixed_case_monkey'
+require 'models/edge'
 
 class PrimaryKeysTest < ActiveRecord::TestCase
   fixtures :topics, :subscribers, :movies, :mixed_case_monkeys
@@ -161,4 +162,17 @@ class PrimaryKeysTest < ActiveRecord::TestCase
 
     assert_equal 'foo', model.primary_key
   end
+
+  def test_no_primary_key_raises
+    assert_raises(ActiveRecord::UnknownPrimaryKey) do
+      Edge.primary_key
+    end
+
+    begin
+      Edge.primary_key
+    rescue ActiveRecord::UnknownPrimaryKey => e
+      assert e.message.include?('edges')
+      assert e.message.include?('Edge')
+    end
+  end
 end