Allow proc defaults with the Attributes API

This is a variant implementation of the changes proposed in #19914.
Unlike that PR, the change in behavior is isolated in its own class.
This is to prevent wonky behavior if a Proc is assigned outside of the
default, and it is a natural place to place the behavior required by #19921
as well.

Close #19914.

[Sean Griffin & Kir Shatrov]

1 files changed, 10 insertions, 0 deletions

diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 927d7950a5..4619293ac6 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -125,6 +125,16 @@ module ActiveRecord
       assert_equal "from user", model.wibble
     end
 
+    test "procs for default values" do
+      klass = Class.new(OverloadedType) do
+        @@counter = 0
+        attribute :counter, :integer, default: -> { @@counter += 1 }
+      end
+
+      assert_equal 1, klass.new.counter
+      assert_equal 2, klass.new.counter
+    end
+
     if current_adapter?(:PostgreSQLAdapter)
       test "arrays types can be specified" do
         klass = Class.new(OverloadedType) do