Improve the derivation of HABTM assocation join table names

Improve the derivation of HABTM join table name to take account of nesting.
It now takes the table names of the two models, sorts them lexically and
then joins them, stripping any common prefix from the second table name.

Some examples:

  Top level models
  (Category <=> Product)
  Old: categories_products
  New: categories_products

  Top level models with a global table_name_prefix
  (Category <=> Product)
  Old: site_categories_products
  New: site_categories_products

  Nested models in a module without a table_name_prefix method
  (Admin::Category <=> Admin::Product)
  Old: categories_products
  New: categories_products

  Nested models in a module with a table_name_prefix method
  (Admin::Category <=> Admin::Product)
  Old: categories_products
  New: admin_categories_products

  Nested models in a parent model
  (Catalog::Category <=> Catalog::Product)
  Old: categories_products
  New: catalog_categories_products

  Nested models in different parent models
  (Catalog::Category <=> Content::Page)
  Old: categories_pages
  New: catalog_categories_content_pages

Also as part of this commit the validity checks for HABTM assocations have
been moved to ActiveRecord::Reflection One side effect of this is to move when
the exceptions are raised from the point of declaration to when the association
is built. This is consistant with other association validity checks.

13 files changed, 85 insertions, 52 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 10bfe1945a..d759b26c65 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,44 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Improve the derivation of HABTM join table name to take account of nesting.
+    It now takes the table names of the two models, sorts them lexically and
+    then joins them, stripping any common prefix from the second table name.
+
+    Some examples:
+
+        Top level models (Category <=> Product)
+        Old: categories_products
+        New: categories_products
+
+        Top level models with a global table_name_prefix (Category <=> Product)
+        Old: site_categories_products
+        New: site_categories_products
+
+        Nested models in a module without a table_name_prefix method (Admin::Category <=> Admin::Product)
+        Old: categories_products
+        New: categories_products
+
+        Nested models in a module with a table_name_prefix method (Admin::Category <=> Admin::Product)
+        Old: categories_products
+        New: admin_categories_products
+
+        Nested models in a parent model (Catalog::Category <=> Catalog::Product)
+        Old: categories_products
+        New: catalog_categories_products
+
+        Nested models in different parent models (Catalog::Category <=> Content::Page)
+        Old: categories_pages
+        New: catalog_categories_content_pages
+
+    *Andrew White*
+
+*   Move HABTM validity checks to ActiveRecord::Relation. One side effect of
+    this is to move when the exceptions are raised from the point of declaration
+    to when the association is built. This is consistant with other association
+    validity checks.
+
+    *Andrew White*
+
 *   Added `stored_attributes` hash which contains the attributes stored using
     ActiveRecord::Store. This allows you to retrieve the list of attributes
     you've defined.
diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index 30fc44b4c2..f7656ecd47 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -6,7 +6,6 @@ module ActiveRecord::Associations::Builder
 
     def build
       reflection = super
-      check_validity(reflection)
       define_destroy_hook
       reflection
     end
@@ -24,34 +23,5 @@ module ActiveRecord::Associations::Builder
           RUBY
         })
       end
-
-      # TODO: These checks should probably be moved into the Reflection, and we should not be
-      #       redefining the options[:join_table] value - instead we should define a
-      #       reflection.join_table method.
-      def check_validity(reflection)
-        if reflection.association_foreign_key == reflection.foreign_key
-          raise ActiveRecord::HasAndBelongsToManyAssociationForeignKeyNeeded.new(reflection)
-        end
-
-        reflection.options[:join_table] ||= join_table_name(
-          model.send(:undecorated_table_name, model.to_s),
-          model.send(:undecorated_table_name, reflection.class_name)
-        )
-      end
-
-      # Generates a join table name from two provided table names.
-      # The names in the join table names end up in lexicographic order.
-      #
-      #   join_table_name("members", "clubs")         # => "clubs_members"
-      #   join_table_name("members", "special_clubs") # => "members_special_clubs"
-      def join_table_name(first_table_name, second_table_name)
-        if first_table_name < second_table_name
-          join_table = "#{first_table_name}_#{second_table_name}"
-        else
-          join_table = "#{second_table_name}_#{first_table_name}"
-        end
-
-        model.table_name_prefix + join_table + model.table_name_suffix
-      end
   end
 end
diff --git a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
index 58d041ec1d..93618721bb 100644
--- a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
@@ -5,7 +5,7 @@ module ActiveRecord
       attr_reader :join_table
 
       def initialize(owner, reflection)
-        @join_table = Arel::Table.new(reflection.options[:join_table])
+        @join_table = Arel::Table.new(reflection.join_table)
         super
       end
 
diff --git a/activerecord/lib/active_record/associations/join_helper.rb b/activerecord/lib/active_record/associations/join_helper.rb
index cea6ad6944..5a41b40c8f 100644
--- a/activerecord/lib/active_record/associations/join_helper.rb
+++ b/activerecord/lib/active_record/associations/join_helper.rb
@@ -19,7 +19,7 @@ module ActiveRecord
 
           if reflection.source_macro == :has_and_belongs_to_many
             tables << alias_tracker.aliased_table_for(
-              (reflection.source_reflection || reflection).options[:join_table],
+              (reflection.source_reflection || reflection).join_table,
               table_alias_for(reflection, true)
             )
           end
diff --git a/activerecord/lib/active_record/associations/preloader/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/preloader/has_and_belongs_to_many.rb
index b77b667219..8e8925f0a9 100644
--- a/activerecord/lib/active_record/associations/preloader/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_and_belongs_to_many.rb
@@ -6,7 +6,7 @@ module ActiveRecord
 
         def initialize(klass, records, reflection, preload_options)
           super
-          @join_table = Arel::Table.new(options[:join_table]).alias('t0')
+          @join_table = Arel::Table.new(reflection.join_table).alias('t0')
         end
 
         # Unlike the other associations, we want to get a raw array of rows so that we can
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index 7e6512501c..96d24b72b3 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -594,7 +594,7 @@ module ActiveRecord
             when :has_and_belongs_to_many
               if (targets = row.delete(association.name.to_s))
                 targets = targets.is_a?(Array) ? targets : targets.split(/\s*,\s*/)
-                table_name = association.options[:join_table]
+                table_name = association.join_table
                 rows[table_name].concat targets.map { |target|
                   { association.foreign_key             => row[primary_key_name],
                     association.association_foreign_key => ActiveRecord::Fixtures.identify(target) }
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index e9a8e90538..0d9534acd6 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -161,6 +161,10 @@ module ActiveRecord
         @quoted_table_name ||= klass.quoted_table_name
       end
 
+      def join_table
+        @join_table ||= options[:join_table] || derive_join_table
+      end
+
       def foreign_key
         @foreign_key ||= options[:foreign_key] || derive_foreign_key
       end
@@ -208,6 +212,10 @@ module ActiveRecord
 
       def check_validity!
         check_validity_of_inverse!
+
+        if has_and_belongs_to_many? && association_foreign_key == foreign_key
+          raise HasAndBelongsToManyAssociationForeignKeyNeeded.new(self)
+        end
       end
 
       def check_validity_of_inverse!
@@ -290,6 +298,10 @@ module ActiveRecord
         macro == :belongs_to
       end
 
+      def has_and_belongs_to_many?
+        macro == :has_and_belongs_to_many
+      end
+
       def association_class
         case macro
         when :belongs_to
@@ -332,6 +344,10 @@ module ActiveRecord
           end
         end
 
+        def derive_join_table
+          [active_record.table_name, klass.table_name].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_")
+        end
+
         def primary_key(klass)
           klass.primary_key || raise(UnknownPrimaryKey.new(klass))
         end
diff --git a/activerecord/test/cases/adapters/mysql/reserved_word_test.rb b/activerecord/test/cases/adapters/mysql/reserved_word_test.rb
index 6faceaf7c0..8e3eeac81e 100644
--- a/activerecord/test/cases/adapters/mysql/reserved_word_test.rb
+++ b/activerecord/test/cases/adapters/mysql/reserved_word_test.rb
@@ -34,11 +34,11 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
       'select'=>'id int auto_increment primary key',
       'values'=>'id int auto_increment primary key, group_id int',
       'distinct'=>'id int auto_increment primary key',
-      'distincts_selects'=>'distinct_id int, select_id int'
+      'distinct_select'=>'distinct_id int, select_id int'
   end
 
   def teardown
-    drop_tables_directly ['group', 'select', 'values', 'distinct', 'distincts_selects', 'order']
+    drop_tables_directly ['group', 'select', 'values', 'distinct', 'distinct_select', 'order']
   end
 
   # create tables with reserved-word names and columns
@@ -80,7 +80,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   #activerecord model class with reserved-word table name
   def test_activerecord_model
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     x = nil
     assert_nothing_raised { x = Group.new }
     x.order = 'x'
@@ -94,7 +94,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # has_one association with reserved-word table name
   def test_has_one_associations
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     v = nil
     assert_nothing_raised { v = Group.find(1).values }
     assert_equal 2, v.id
@@ -102,7 +102,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # belongs_to association with reserved-word table name
   def test_belongs_to_associations
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     gs = nil
     assert_nothing_raised { gs = Select.find(2).groups }
     assert_equal gs.length, 2
@@ -111,7 +111,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # has_and_belongs_to_many with reserved-word table name
   def test_has_and_belongs_to_many
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     s = nil
     assert_nothing_raised { s = Distinct.find(1).selects }
     assert_equal s.length, 2
diff --git a/activerecord/test/cases/adapters/mysql2/reserved_word_test.rb b/activerecord/test/cases/adapters/mysql2/reserved_word_test.rb
index 32d4282623..5c2c113c78 100644
--- a/activerecord/test/cases/adapters/mysql2/reserved_word_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/reserved_word_test.rb
@@ -34,11 +34,11 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
       'select'=>'id int auto_increment primary key',
       'values'=>'id int auto_increment primary key, group_id int',
       'distinct'=>'id int auto_increment primary key',
-      'distincts_selects'=>'distinct_id int, select_id int'
+      'distinct_select'=>'distinct_id int, select_id int'
   end
 
   def teardown
-    drop_tables_directly ['group', 'select', 'values', 'distinct', 'distincts_selects', 'order']
+    drop_tables_directly ['group', 'select', 'values', 'distinct', 'distinct_select', 'order']
   end
 
   # create tables with reserved-word names and columns
@@ -80,7 +80,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   #activerecord model class with reserved-word table name
   def test_activerecord_model
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     x = nil
     assert_nothing_raised { x = Group.new }
     x.order = 'x'
@@ -94,7 +94,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # has_one association with reserved-word table name
   def test_has_one_associations
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     v = nil
     assert_nothing_raised { v = Group.find(1).values }
     assert_equal 2, v.id
@@ -102,7 +102,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # belongs_to association with reserved-word table name
   def test_belongs_to_associations
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     gs = nil
     assert_nothing_raised { gs = Select.find(2).groups }
     assert_equal gs.length, 2
@@ -111,7 +111,7 @@ class MysqlReservedWordTest < ActiveRecord::TestCase
 
   # has_and_belongs_to_many with reserved-word table name
   def test_has_and_belongs_to_many
-    create_test_fixtures :select, :distinct, :group, :values, :distincts_selects
+    create_test_fixtures :select, :distinct, :group, :values, :distinct_select
     s = nil
     assert_nothing_raised { s = Distinct.find(1).selects }
     assert_equal s.length, 2
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 9d693bae0c..24bb4adf0a 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -773,9 +773,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
 
   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
+      SelfMember.new.friends
     }
   end
 
diff --git a/activerecord/test/fixtures/reserved_words/distincts_selects.yml b/activerecord/test/fixtures/reserved_words/distinct_select.yml
index 90e8c95fef..d96779ade4 100644
--- a/activerecord/test/fixtures/reserved_words/distincts_selects.yml
+++ b/activerecord/test/fixtures/reserved_words/distinct_select.yml
@@ -1,11 +1,11 @@
-distincts_selects1:
+distinct_select1:
   distinct_id: 1
   select_id: 1
 
-distincts_selects2:
+distinct_select2:
   distinct_id: 1
   select_id: 2
 
-distincts_selects3:
+distinct_select3:
   distinct_id: 2
   select_id: 3
diff --git a/activerecord/test/models/member.rb b/activerecord/test/models/member.rb
index 11a0f4ff63..1f719b0858 100644
--- a/activerecord/test/models/member.rb
+++ b/activerecord/test/models/member.rb
@@ -30,3 +30,8 @@ class Member < ActiveRecord::Base
   has_many :current_memberships, :conditions => { :favourite => true }
   has_many :clubs, :through => :current_memberships
 end
+
+class SelfMember < ActiveRecord::Base
+  self.table_name = "members"
+  has_and_belongs_to_many :friends, :class_name => "SelfMember", :join_table => "member_friends"
+end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 5bcb9652cd..ba01ef35f0 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -361,6 +361,11 @@ ActiveRecord::Schema.define do
     t.string :extra_data
   end
 
+  create_table :member_friends, :force => true, :id => false do |t|
+    t.integer :member_id
+    t.integer :friend_id
+  end
+
   create_table :memberships, :force => true do |t|
     t.datetime :joined_on
     t.integer :club_id, :member_id