Move writing unknown column exception to null attribute

Making this change revealed several subtle bugs related to models with
no primary key, and anonymous classes. These have been fixed as well,
with regression tests added.

activerecord/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Fix subtle bugs regarding attribute assignment on models with no primary
+    key. `'id'` will no longer be part of the attributes hash.
+
+    *Sean Griffin*
+
 *   Deprecate automatic counter caches on `has_many :through`. The behavior was
     broken and inconsistent.
 

activerecord/lib/active_record/attribute.rb

@@ -90,6 +90,11 @@ def initialize(name)
       def value
         nil
       end
+
+      def with_value_from_database(value)
+        raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{name}`"
+      end
+      alias_method :with_value_from_user, :with_value_from_database
     end
 
     class Uninitialized < Attribute # :nodoc:

activerecord/lib/active_record/attribute_methods/primary_key.rb

@@ -83,12 +83,9 @@ def reset_primary_key #:nodoc:
         end
 
         def get_primary_key(base_name) #:nodoc:
-          return 'id' if base_name.blank?
-
-          case primary_key_prefix_type
-          when :table_name
+          if base_name && primary_key_prefix_type == :table_name
             base_name.foreign_key(false)
-          when :table_name_with_underscore
+          elsif base_name && primary_key_prefix_type == :table_name_with_underscore
             base_name.foreign_key
           else
             if ActiveRecord::Base != self && table_exists?

activerecord/lib/active_record/attribute_methods/write.rb

@@ -70,10 +70,6 @@ def write_attribute_with_type_cast(attr_name, value, should_type_cast)
         attr_name = attr_name.to_s
         attr_name = self.class.primary_key if attr_name == 'id' && self.class.primary_key
 
-        unless has_attribute?(attr_name) || self.class.columns_hash.key?(attr_name)
-          raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{attr_name}'"
-        end
-
         if should_type_cast
           @attributes.write_from_user(attr_name, value)
         else

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -381,7 +381,7 @@ def tables(name = nil, database = nil, like = nil) #:nodoc:
       end
 
       def table_exists?(name)
-        return false unless name
+        return false unless name.present?
         return true if tables(nil, nil, name).any?
 
         name          = name.to_s

activerecord/lib/active_record/core.rb

@@ -521,7 +521,7 @@ def to_ary # :nodoc:
 
     def init_internals
       pk = self.class.primary_key
-      unless @attributes.include?(pk)
+      if pk && !@attributes.include?(pk)
         @attributes.write_from_database(pk, nil)
       end
 

activerecord/test/cases/attribute_methods_test.rb

@@ -253,6 +253,15 @@ def test_case_sensitive_attributes_hash
     assert_equal @loaded_fixtures['computers']['workstation'].to_hash, Computer.first.attributes
   end
 
+  def test_attributes_without_primary_key
+    klass = Class.new(ActiveRecord::Base) do
+      self.table_name = 'developers_projects'
+    end
+
+    assert_equal klass.column_names, klass.new.attributes.keys
+    assert_not klass.new.attributes.key?('id')
+  end
+
   def test_hashes_not_mangled
     new_topic = { :title => "New Topic" }
     new_topic_values = { :title => "AnotherTopic" }

activerecord/test/cases/primary_keys_test.rb

@@ -134,14 +134,22 @@ def test_supports_primary_key
   end
 
   def test_primary_key_returns_value_if_it_exists
+    klass = Class.new(ActiveRecord::Base) do
+      self.table_name = 'developers'
+    end
+
     if ActiveRecord::Base.connection.supports_primary_key?
-      assert_equal 'id', ActiveRecord::Base.connection.primary_key('developers')
+      assert_equal 'id', klass.primary_key
     end
   end
 
   def test_primary_key_returns_nil_if_it_does_not_exist
+    klass = Class.new(ActiveRecord::Base) do
+      self.table_name = 'developers_projects'
+    end
+
     if ActiveRecord::Base.connection.supports_primary_key?
-      assert_nil ActiveRecord::Base.connection.primary_key('developers_projects')
+      assert_nil klass.primary_key
     end
   end
 

activerecord/test/models/contact.rb

@@ -8,6 +8,7 @@ def self.extended(base)
         table_name => 'id'
       }
 
+      column :id,             :integer
       column :name,           :string
       column :age,            :integer
       column :avatar,         :binary