Introduce `reload_<association>` reader for singular associations.

This patch brings back the functionality of passing true to the
association proxy. The behavior was deprecated with #20888 and scheduled
for removal in Rails 5.1.

The deprecation mentioned that instead of `Article.category(true)` one
should use `article#reload.category`. Unfortunately the alternative does
not expose the same behavior as passing true to the reader
did. Specifically reloading the parent record throws unsaved changes and
other caches away. Passing true only affected the association.

This is problematic and there is no easy workaround. I propose to bring
back the old functionality by introducing this new reader method for
singular associations.

2 files changed, 20 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 6b7e4fee56..72f1b3b125 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -291,6 +291,16 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert client.account.new_record?
   end
 
+  def test_reloading_the_belonging_object
+    odegy_account = accounts(:odegy_account)
+
+    assert_equal "Odegy", odegy_account.firm.name
+    Company.where(id: odegy_account.firm_id).update_all(name: "ODEGY")
+    assert_equal "Odegy", odegy_account.firm.name
+
+    assert_equal "ODEGY", odegy_account.reload_firm.name
+  end
+
   def test_natural_assignment_to_nil
     client = Client.find(3)
     client.firm = nil
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index 862f33a1a0..48fbc5990c 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -326,6 +326,16 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_reload_association
+    odegy = companies(:odegy)
+
+    assert_equal 53, odegy.account.credit_limit
+    Account.where(id: odegy.account.id).update_all(credit_limit: 80)
+    assert_equal 53, odegy.account.credit_limit
+
+    assert_equal 80, odegy.reload_account.credit_limit
+  end
+
   def test_build
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.save