Merge pull request rails#42198 from zetlanddk/remove-dangling-migrations

Handle duplicate migration names in multi db

Author: eileencodes

activerecord/lib/active_record/migration.rb

@@ -1044,7 +1044,9 @@ def migration
       end
 
       def load_migration
-        require(File.expand_path(filename))
+        Object.send(:remove_const, name) rescue nil
+
+        load(File.expand_path(filename))
         name.constantize.new(name, version)
       end
   end

activerecord/test/cases/migration_test.rb

@@ -15,6 +15,12 @@
 require MIGRATIONS_ROOT + "/rename/2_rename_things"
 require MIGRATIONS_ROOT + "/decimal/1_give_me_big_numbers"
 
+class ValidPeopleHaveLastNames < ActiveRecord::Migration::Current
+  def change
+    drop_table :people
+  end
+end
+
 class BigNumber < ActiveRecord::Base
   unless current_adapter?(:PostgreSQLAdapter, :SQLite3Adapter)
     attribute :value_of_e, :integer
@@ -108,6 +114,14 @@ def test_migrator_versions
     assert_equal true, migrator.needs_migration?
   end
 
+  def test_name_collision_across_dbs
+    migrations_path = MIGRATIONS_ROOT + "/valid"
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
+    migrator.up
+
+    assert_column Person, :last_name
+  end
+
   def test_migration_detection_without_schema_migration_table
     ActiveRecord::Base.connection.drop_table "schema_migrations", if_exists: true