Ensure self referential HABTM associations raise an exception if asso…

…ciation_foreign_key is missing. [#1252 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

activerecord/lib/active_record/associations.rb

@@ -51,6 +51,12 @@ def initialize(owner, reflection)
     end
   end
 
+  class HasAndBelongsToManyAssociationForeignKeyNeeded < ActiveRecordError #:nodoc:
+    def initialize(reflection)
+      super("Cannot create self referential has_and_belongs_to_many association on '#{reflection.class_name rescue nil}##{reflection.name rescue nil}'. :association_foreign_key cannot be the same as the :foreign_key.")
+    end
+  end
+
   class EagerLoadPolymorphicError < ActiveRecordError #:nodoc:
     def initialize(reflection)
       super("Can not eagerly load the polymorphic association #{reflection.name.inspect}")
@@ -1526,6 +1532,10 @@ def create_has_and_belongs_to_many_reflection(association_id, options, &extensio
           options[:extend] = create_extension_modules(association_id, extension, options[:extend])
 
           reflection = create_reflection(:has_and_belongs_to_many, association_id, options, self)
+
+          if reflection.association_foreign_key == reflection.primary_key_name
+            raise HasAndBelongsToManyAssociationForeignKeyNeeded.new(reflection)
+          end
 
           reflection.options[:join_table] ||= join_table_name(undecorated_table_name(self.to_s), undecorated_table_name(reflection.class_name))
 

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -740,6 +740,14 @@ def test_symbols_as_keys
     assert_equal developer, project.developers.find(:first)
     assert_equal project, developer.projects.find(:first)
   end
+
+  def test_self_referential_habtm_without_foreign_key_set_should_raise_exception
+    assert_raise(ActiveRecord::HasAndBelongsToManyAssociationForeignKeyNeeded) {
+      Member.class_eval do
+        has_and_belongs_to_many :friends, :class_name => "Member", :join_table => "member_friends"
+      end
+    }
+  end
 
   def test_dynamic_find_should_respect_association_include
     # SQL error in sort clause if :include is not included