Eager belongs_to :include infers the foreign key from the association name...

Eager belongs_to :include infers the foreign key from the association name rather than the class name. Closes #10517.


git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8456 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Eager belongs_to :include infers the foreign key from the association name rather than the class name.  #10517 [Jonathan Viney]
+
 * SQLite: fix rename_ and remove_column for columns with unique indexes.  #10576 [Brandon Keepers]
 
 * Ruby 1.9 compatibility.  [Jeremy Kemper]

activerecord/lib/active_record/associations.rb

@@ -772,8 +772,8 @@ def has_one(association_id, options = {})
       # * <tt>:order</tt>       - specify the order in which the associated objects are returned as an <tt>ORDER BY</tt> SQL fragment,
       #   such as <tt>last_name, first_name DESC</tt>
       # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
-      #   of the associated class in lower-case and +_id+ suffixed. So a +Person+ class that makes a +belongs_to+ association to a
-      #   +Boss+ class will use +boss_id+ as the default +foreign_key+.
+      #   of the association with an +_id+ suffix. So a class that defines a +belongs_to :person+ association will use +person_id+ as the default +foreign_key+.
+      #   Similarly, +belongs_to :favorite_person, :class_name => "Person"+ will use a foreign key of +favorite_person_id+.
       # * <tt>:counter_cache</tt> - caches the number of belonging objects on the associate class through the use of +increment_counter+ 
       #   and +decrement_counter+. The counter cache is incremented when an object of this class is created and decremented when it's
       #   destroyed. This requires that a column named <tt>#{table_name}_count</tt> (such as +comments_count+ for a belonging +Comment+ class)
@@ -1707,7 +1707,7 @@ def association_join
 		     connection.quote_table_name(aliased_table_name),
 		     reflection.klass.primary_key,
                      connection.quote_table_name(parent.aliased_table_name),
-		     options[:foreign_key] || klass.to_s.foreign_key
+		     options[:foreign_key] || reflection.primary_key_name
                     ]
                 else
                   ""

activerecord/test/associations/eager_test.rb

@@ -115,6 +115,11 @@ def test_eager_association_loading_with_belongs_to_and_limit_and_offset_and_mult
     assert_equal [2], posts.collect { |p| p.id }
   end
   
+  def test_eager_association_loading_with_belongs_to_inferred_foreign_key_from_association_name
+    author_favorite = AuthorFavorite.find(:first, :include => :favorite_author)
+    assert_equal authors(:mary), assert_no_queries { author_favorite.favorite_author }
+  end
+
   def test_eager_association_loading_with_explicit_join
     posts = Post.find(:all, :include => :comments, :joins => "INNER JOIN authors ON posts.author_id = authors.id AND authors.name = 'Mary'", :limit => 1, :order => 'author_id')
     assert_equal 1, posts.length

activerecord/test/fixtures/author.rb

@@ -105,5 +105,5 @@ class AuthorAddress < ActiveRecord::Base
 
 class AuthorFavorite < ActiveRecord::Base
   belongs_to :author
-  belongs_to :favorite_author, :class_name => "Author", :foreign_key => 'favorite_author_id'
+  belongs_to :favorite_author, :class_name => "Author"
 end