Merge pull request rails#54892 from Shopify/alloc_association_cache

Allow allocated Active Records to lookup associations

Author: gmcgibbon

activerecord/CHANGELOG.md

@@ -1,3 +1,11 @@
+*   Allow allocated Active Records to lookup associations.
+
+    Previously, the association cache isn't setup on allocated record objects, so association
+    lookups will crash. Test frameworks like mocha use allocate to check for stubbable instance
+    methods, which can trigger an association lookup.
+
+    *Gannon McGibbon*
+
 *   Encryption now supports `support_unencrypted_data: true` being set per-attribute.
 
     Previously this only worked if `ActiveRecord::Encryption.config.support_unencrypted_data == true`.

activerecord/lib/active_record/associations.rb

@@ -79,7 +79,7 @@ def init_internals
 
       # Returns the specified association instance if it exists, +nil+ otherwise.
       def association_instance_get(name)
-        @association_cache[name]
+        (@association_cache ||= {})[name]
       end
 
       # Set the specified association instance.

activerecord/test/cases/associations_test.rb

@@ -59,6 +59,10 @@ def test_eager_loading_should_not_change_count_of_children
     assert_equal 1, liquids[0].molecules.length
   end
 
+  def test_allocated_record_can_see_assocations
+    assert_not_nil Ship.allocate.association(:parts)
+  end
+
   def test_subselect
     author = authors :david
     favs = author.author_favorites