Add foreign_type option for polymorphic has_one and has_many.

To be possible to use a custom column name to save/read the polymorphic
associated type in a has_many or has_one polymorphic association, now users
can use the option :foreign_type to inform in what column the associated object
type will be saved.

4 files changed, 15 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index eb21712f96..cd5fdd5964 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1176,6 +1176,12 @@ module ActiveRecord
       #   Specify the foreign key used for the association. By default this is guessed to be the name
       #   of this class in lower-case and "_id" suffixed. So a Person class that makes a +has_many+
       #   association will use "person_id" as the default <tt>:foreign_key</tt>.
+      # [:foreign_type]
+      #   Specify the column used to store the associated object's type, if this is a polymorphic
+      #   association. By default this is guessed to be the name of the polymorphic association
+      #   specified on "as" option with a "_type" suffix. So a class that defines a
+      #   <tt>has_many :tags, as: :taggable</tt> association will use "taggable_type" as the
+      #   default <tt>:foreign_type</tt>.
       # [:primary_key]
       #   Specify the name of the column to use as the primary key for the association. By default this is +id+.
       # [:dependent]
@@ -1323,6 +1329,12 @@ module ActiveRecord
       #   Specify the foreign key used for the association. By default this is guessed to be the name
       #   of this class in lower-case and "_id" suffixed. So a Person class that makes a +has_one+ association
       #   will use "person_id" as the default <tt>:foreign_key</tt>.
+      # [:foreign_type]
+      #   Specify the column used to store the associated object's type, if this is a polymorphic
+      #   association. By default this is guessed to be the name of the polymorphic association
+      #   specified on "as" option with a "_type" suffix. So a class that defines a
+      #   <tt>has_one :tag, as: :taggable</tt> association will use "taggable_type" as the
+      #   default <tt>:foreign_type</tt>.
       # [:primary_key]
       #   Specify the method that returns the primary key used for the association. By default this is +id+.
       # [:as]
diff --git a/activerecord/lib/active_record/associations/builder/has_many.rb b/activerecord/lib/active_record/associations/builder/has_many.rb
index 4c8c826f76..1b87f92170 100644
--- a/activerecord/lib/active_record/associations/builder/has_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_many.rb
@@ -5,7 +5,7 @@ module ActiveRecord::Associations::Builder
     end
 
     def valid_options
-      super + [:primary_key, :dependent, :as, :through, :source, :source_type, :inverse_of, :counter_cache, :join_table]
+      super + [:primary_key, :dependent, :as, :through, :source, :source_type, :inverse_of, :counter_cache, :join_table, :foreign_type]
     end
 
     def self.valid_dependent_options
diff --git a/activerecord/lib/active_record/associations/builder/has_one.rb b/activerecord/lib/active_record/associations/builder/has_one.rb
index c194c8ae9a..1387717396 100644
--- a/activerecord/lib/active_record/associations/builder/has_one.rb
+++ b/activerecord/lib/active_record/associations/builder/has_one.rb
@@ -5,7 +5,7 @@ module ActiveRecord::Associations::Builder
     end
 
     def valid_options
-      valid = super + [:as]
+      valid = super + [:as, :foreign_type]
       valid += [:through, :source, :source_type] if options[:through]
       valid
     end
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 4202bc5665..9849e03036 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -277,7 +277,7 @@ module ActiveRecord
       def initialize(name, scope, options, active_record)
         super
         @automatic_inverse_of = nil
-        @type         = options[:as] && "#{options[:as]}_type"
+        @type         = options[:as] && (options[:foreign_type] || "#{options[:as]}_type")
         @foreign_type = options[:foreign_type] || "#{name}_type"
         @constructable = calculate_constructable(macro, options)
         @association_scope_cache = {}