Use alias_attribute to provide #id_value alias for #id

This allows access to the raw id column value on records for which an
id column exists but is not the primary key. This is common amongst
models with composite primary keys.

Author: adrianna-chang-shopify

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Add `ActiveRecord::Base#id_value` alias to access the raw value of a record's id column.
+
+    This alias is only provided for models that declare an `:id` column.
+
+    *Adrianna Chang*
+
 *   Fix previous change tracking for `ActiveRecord::Store` when using a column with JSON structured database type
 
     Before, the methods to access the changes made during the last save `#saved_change_to_key?`, `#saved_change_to_key`, and `#key_before_last_save` did not work if the store was defined as a `store_accessor` on a column with a JSON structured database type

activerecord/lib/active_record/model_schema.rb

@@ -618,6 +618,7 @@ def load_schema!
               default: column.default,
               user_provided_default: false
             )
+            alias_attribute :id_value, :id if name == "id"
           end
 
           super

activerecord/test/cases/attribute_methods_test.rb

@@ -44,6 +44,26 @@ def setup
     assert_equal(123_456, order.id_value)
   end
 
+  test "#id_value alias returns the value in the id column, when id column exists" do
+    topic = Topic.new
+    assert_nil topic.id_value
+
+    topic = Topic.find(1)
+    assert_equal 1, topic.id_value
+  end
+
+  test "#id_value alias is not defined if id column doesn't exist" do
+    keyboard = Keyboard.create!
+
+    assert_empty keyboard.attribute_aliases
+  end
+
+  test "#id_value alias returns id column only for composite primary key models" do
+    order = ::Cpk::Order.create(id: [1, 2])
+
+    assert_equal 2, order.id_value
+  end
+
   test "attribute_for_inspect with a string" do
     t = topics(:first)
     t.title = "The First Topic Now Has A Title With\nNewlines And More Than 50 Characters"