From e43e8e268f0522f9f11f4eacae1d04afca768c9b Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Tue, 18 Dec 2012 23:32:45 -0500
Subject: Make change_table reversible when possible [#8267]

---
 .../lib/active_record/migration/command_recorder.rb  |  6 +++++-
 .../test/cases/migration/command_recorder_test.rb    | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index 4ea709fe69..f738c909bc 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -70,7 +70,7 @@ module ActiveRecord
         super || delegate.respond_to?(*args)
       end
 
-      [:create_table, :create_join_table, :change_table, :rename_table, :add_column, :remove_column,
+      [:create_table, :create_join_table, :rename_table, :add_column, :remove_column,
         :rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps,
         :change_column, :change_column_default, :add_reference, :remove_reference, :transaction,
         :drop_join_table, :drop_table, :remove_columns, :remove_index,
@@ -84,6 +84,10 @@ module ActiveRecord
       alias :add_belongs_to :add_reference
       alias :remove_belongs_to :remove_reference
 
+      def change_table(table_name, options = {})
+        yield ConnectionAdapters::Table.new(table_name, self)
+      end
+
       private
 
       module StraightReversions
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 1c5530a132..b406beba06 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -77,6 +77,26 @@ module ActiveRecord
                       [:drop_table, ["figs"], block]], @recorder.commands
       end
 
+      def test_invert_change_table
+        @recorder.revert do
+          @recorder.change_table :fruits do |t|
+            t.string :name
+            t.rename :kind, :cultivar
+          end
+        end
+        assert_equal [
+          [:rename_column, [:fruits, :cultivar, :kind]],
+          [:remove_column, [:fruits, :name, :string, {}], nil],
+        ], @recorder.commands
+
+        assert_raises(ActiveRecord::IrreversibleMigration) do
+          @recorder.revert do
+            @recorder.change_table :fruits do |t|
+              t.remove :kind
+            end
+          end
+        end
+      end
 
       def test_invert_create_table
         @recorder.revert do
-- 
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