Allow delegated_type to be specified primary_key and foreign_key

Since delegated_type assumes that the foreign_key ends with `_id`,
`singular_id` defined by it does not work when the foreign_key does
not end with `id`. This commit fixes it by taking into account
`primary_key` and `foreign_key` in the options.

activerecord/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Allow delegated_type to be specified primary_key and foreign_key.
+
+    Since delegated_type assumes that the foreign_key ends with `_id`,
+    `singular_id` defined by it does not work when the foreign_key does
+    not end with `id`. This change fixes it by taking into account
+    `primary_key` and `foreign_key` in the options.
+
+    *Ryota Egusa*
+
 *   Restore possibility of passing `false` to :polymorphic option of `belongs_to`.
 
     Previously, passing `false` would trigger the option validation logic

activerecord/lib/active_record/delegated_type.rb

@@ -156,8 +156,6 @@ module ActiveRecord
     #   Entry#comment         # => returns the comment record, when entryable_type == "Comment", otherwise nil
     #   Entry#comment_id      # => returns entryable_id, when entryable_type == "Comment", otherwise nil
     #
-    # The +options+ are passed directly to the +belongs_to+ call, so this is where you declare +dependent+ etc.
-    #
     # You can also declare namespaced types:
     #
     #   class Entry < ApplicationRecord
@@ -167,15 +165,38 @@ module ActiveRecord
     #   Entry.access_notice_messages
     #   entry.access_notice_message
     #   entry.access_notice_message?
+    #
+    # === Options
+    #
+    # The +options+ are passed directly to the +belongs_to+ call, so this is where you declare +dependent+ etc.
+    # The following options can be included to specialize the behavior of the delegated type convenience methods.
+    #
+    # [:foreign_key]
+    #   Specify the foreign key used for the convenience methods. By default this is guessed to be the passed
+    #   +role+ with an "_id" suffix. So a class that defines a
+    #   <tt>delegated_type :entryable, types: %w[ Message Comment ]</tt> association will use "entryable_id" as
+    #   the default <tt>:foreign_key</tt>.
+    # [:primary_key]
+    #   Specify the method that returns the primary key of associated object used for the convenience methods.
+    #   By default this is +id+.
+    #
+    # Option examples:
+    #   class Entry < ApplicationRecord
+    #     delegated_type :entryable, types: %w[ Message Comment ], primary_key: :uuid, foreign_key: :entryable_uuid
+    #   end
+    #
+    #   Entry#message_uuid      # => returns entryable_uuid, when entryable_type == "Message", otherwise nil
+    #   Entry#comment_uuid      # => returns entryable_uuid, when entryable_type == "Comment", otherwise nil
     def delegated_type(role, types:, **options)
       belongs_to role, options.delete(:scope), **options.merge(polymorphic: true)
-      define_delegated_type_methods role, types: types
+      define_delegated_type_methods role, types: types, options: options
     end
 
     private
-      def define_delegated_type_methods(role, types:)
+      def define_delegated_type_methods(role, types:, options:)
+        primary_key = options[:primary_key] || "id"
         role_type = "#{role}_type"
-        role_id   = "#{role}_id"
+        role_id   = options[:foreign_key] || "#{role}_id"
 
         define_method "#{role}_class" do
           public_send("#{role}_type").constantize
@@ -200,7 +221,7 @@ module ActiveRecord
             public_send(role) if public_send(query)
           end
 
-          define_method "#{singular}_id" do
+          define_method "#{singular}_#{primary_key}" do
             public_send(role_id) if public_send(query)
           end
         end

activerecord/test/cases/delegated_type_test.rb

@@ -4,6 +4,9 @@ require "cases/helper"
 require "models/entry"
 require "models/message"
 require "models/comment"
+require "models/uuid_entry"
+require "models/uuid_message"
+require "models/uuid_comment"
 
 class DelegatedTypeTest < ActiveRecord::TestCase
   fixtures :comments
@@ -11,6 +14,11 @@ class DelegatedTypeTest < ActiveRecord::TestCase
   setup do
     @entry_with_message = Entry.create! entryable: Message.new(subject: "Hello world!")
     @entry_with_comment = Entry.create! entryable: comments(:greetings)
+
+    if current_adapter?(:PostgreSQLAdapter)
+      @uuid_entry_with_message = UuidEntry.create! uuid: SecureRandom.uuid, entryable: UuidMessage.new(uuid: SecureRandom.uuid, subject: "Hello world!")
+      @uuid_entry_with_comment = UuidEntry.create! uuid: SecureRandom.uuid, entryable: UuidComment.new(uuid: SecureRandom.uuid, content: "comment")
+    end
   end
 
   test "delegated class" do
@@ -54,4 +62,14 @@ class DelegatedTypeTest < ActiveRecord::TestCase
     assert_equal @entry_with_comment.entryable_id, @entry_with_comment.comment_id
     assert_nil @entry_with_comment.message_id
   end
+
+  test "association uuid" do
+    skip unless current_adapter?(:PostgreSQLAdapter)
+
+    assert_equal @uuid_entry_with_message.entryable_uuid, @uuid_entry_with_message.uuid_message_uuid
+    assert_nil @uuid_entry_with_message.uuid_comment_uuid
+
+    assert_equal @uuid_entry_with_comment.entryable_uuid, @uuid_entry_with_comment.uuid_comment_uuid
+    assert_nil @uuid_entry_with_comment.uuid_message_uuid
+  end
 end

activerecord/test/models/uuid_comment.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class UuidComment < ActiveRecord::Base
+  has_one :uuid_entry, as: :entryable
+end

activerecord/test/models/uuid_entry.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class UuidEntry < ActiveRecord::Base
+  delegated_type :entryable, types: %w[ UuidMessage UuidComment ], primary_key: :uuid, foreign_key: :entryable_uuid
+end

activerecord/test/models/uuid_message.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class UuidMessage < ActiveRecord::Base
+  has_one :uuid_entry, as: :entryable
+end

activerecord/test/schema/postgresql_specific_schema.rb

@@ -104,11 +104,27 @@ _SQL
     t.decimal :decimal_array_default, array: true, default: [1.23, 3.45]
   end
 
+  create_table :uuid_comments, force: true, id: false do |t|
+    t.uuid :uuid, primary_key: true, **uuid_default
+    t.string :content
+  end
+
+  create_table :uuid_entries, force: true, id: false do |t|
+    t.uuid :uuid, primary_key: true, **uuid_default
+    t.string :entryable_type, null: false
+    t.uuid :entryable_uuid, null: false
+  end
+
   create_table :uuid_items, force: true, id: false do |t|
     t.uuid :uuid, primary_key: true, **uuid_default
     t.string :title
   end
 
+  create_table :uuid_messages, force: true, id: false do |t|
+    t.uuid :uuid, primary_key: true, **uuid_default
+    t.string :subject
+  end
+
   if supports_partitioned_indexes?
     create_table(:measurements, id: false, force: true, options: "PARTITION BY LIST (city_id)") do |t|
       t.string :city_id, null: false