Add reversible syntax for change_column_default

Passing `:from` and `:to` to `change_column_default` makes this command
reversible as user has defined its previous state.

So, instead of having the migration command as:

    change_column_default(:posts, :state, "draft")

They can write it as:

    change_column_default(:posts, :state, from: nil, to: "draft")

2 files changed, 17 insertions, 0 deletions

diff --git a/activerecord/test/cases/migration/columns_test.rb b/activerecord/test/cases/migration/columns_test.rb
index 5fc7702dfa..ab3f584350 100644
--- a/activerecord/test/cases/migration/columns_test.rb
+++ b/activerecord/test/cases/migration/columns_test.rb
@@ -267,6 +267,13 @@ module ActiveRecord
         assert_nil TestModel.new.first_name
       end
 
+      def test_change_column_default_with_from_and_to
+        add_column "test_models", "first_name", :string
+        connection.change_column_default "test_models", "first_name", from: nil, to: "Tester"
+
+        assert_equal "Tester", TestModel.new.first_name
+      end
+
       def test_remove_column_no_second_parameter_raises_exception
         assert_raise(ArgumentError) { connection.remove_column("funny") }
       end
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 90b7c6b38a..99f1dc65b0 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -169,6 +169,16 @@ module ActiveRecord
         end
       end
 
+      def test_invert_change_column_default_with_from_and_to
+        change = @recorder.inverse_of :change_column_default, [:table, :column, from: "old_value", to: "new_value"]
+        assert_equal [:change_column_default, [:table, :column, from: "new_value", to: "old_value"]], change
+      end
+
+      def test_invert_change_column_default_with_from_and_to_with_boolean
+        change = @recorder.inverse_of :change_column_default, [:table, :column, from: true, to: false]
+        assert_equal [:change_column_default, [:table, :column, from: false, to: true]], change
+      end
+
       def test_invert_change_column_null
         add = @recorder.inverse_of :change_column_null, [:table, :column, true]
         assert_equal [:change_column_null, [:table, :column, false]], add