making rake:migrate VERSION=0 a noop called in succession. [#2137 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

2 files changed, 26 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index c163fb982a..940f825038 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -384,9 +384,13 @@ module ActiveRecord
     class << self
       def migrate(migrations_path, target_version = nil)
         case
-          when target_version.nil?              then up(migrations_path, target_version)
-          when current_version > target_version then down(migrations_path, target_version)
-          else                                       up(migrations_path, target_version)
+          when target_version.nil?
+            up(migrations_path, target_version)
+          when current_version == 0 && target_version == 0
+          when current_version > target_version
+            down(migrations_path, target_version)
+          else
+            up(migrations_path, target_version)
         end
       end
 
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index 7a26ee072d..a3d1ceaa1f 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -1136,6 +1136,25 @@ if ActiveRecord::Base.connection.supports_migrations?
       load(MIGRATIONS_ROOT + "/valid/1_people_have_last_names.rb")
     end
 
+    def test_target_version_zero_should_run_only_once
+      # migrate up to 1
+      ActiveRecord::Migrator.migrate(MIGRATIONS_ROOT + "/valid", 1)
+
+      # migrate down to 0
+      ActiveRecord::Migrator.migrate(MIGRATIONS_ROOT + "/valid", 0)
+
+      # now unload the migrations that have been defined
+      PeopleHaveLastNames.unloadable
+      ActiveSupport::Dependencies.remove_unloadable_constants!
+
+      # migrate down to 0 again
+      ActiveRecord::Migrator.migrate(MIGRATIONS_ROOT + "/valid", 0)
+
+      assert !defined? PeopleHaveLastNames
+    ensure
+      load(MIGRATIONS_ROOT + "/valid/1_people_have_last_names.rb")
+    end
+
     def test_migrator_db_has_no_schema_migrations_table
       # Oracle adapter raises error if semicolon is present as last character
       if current_adapter?(:OracleAdapter)