NoMethodError: undefined method `perform' for nil:NilClass

[ziaulrehman40]

Hi,

We are in process of upgrading a rails 4.2. app to latest rails version. We successfully upgraded to 5.0 and while upgrading to 5.1 we are blocked by this error, which seems to be coming from strong_migrations.

If i remove strong_migrations from the app, everything works.

Ruby: 2.6.3
Rails: 5.1.7

Caused by:
NoMethodError: undefined method `perform' for nil:NilClass
/.../.rvm/gems/ruby-2.6.3/gems/strong_migrations-0.4.1/lib/strong_migrations/migration.rb:14:in `method_missing'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:600:in `method_missing'
/....../db/migrate/20190802132723_add_xyz_table.rb:2:in `<class:AddXyzTable>'
/....../db/migrate/20190802132723_add_xyz.rb:1:in `<top (required)>'
/.../.rvm/gems/ruby-2.6.3/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `require'
/.../.rvm/gems/ruby-2.6.3/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `block in require'
/.../.rvm/gems/ruby-2.6.3/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:258:in `load_dependency'
/.../.rvm/gems/ruby-2.6.3/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `require'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:962:in `load_migration'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:958:in `migration'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:953:in `disable_ddl_transaction'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1305:in `use_transaction?'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1297:in `ddl_transaction'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1229:in `execute_migration_in_transaction'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1201:in `block in migrate_without_lock'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1200:in `each'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1200:in `migrate_without_lock'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1148:in `block in migrate'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1317:in `with_advisory_lock'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1148:in `migrate'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:1007:in `up'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/migration.rb:985:in `migrate'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/tasks/database_tasks.rb:171:in `migrate'
/.../.rvm/gems/ruby-2.6.3/gems/strong_migrations-0.4.1/lib/strong_migrations/database_tasks.rb:4:in `migrate'
/.../.rvm/gems/ruby-2.6.3/gems/activerecord-5.1.7/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
/.../.rvm/gems/ruby-2.6.3/gems/rake-12.3.3/exe/rake:27:in `<top (required)>'

Our migration is simple, something like:

class AddXyzTable < ActiveRecord::Migration[4.2]
  create_table :xyz do |t|
    t.integer "abc_id",             null: false
    t.integer "efg_id", null: false
  end

  add_index "xyz", ["abc_id", "efg_id"], name: "index_xyz_on_abc_id_and_efg_id", using: :btree
  add_index "xyz", ["efg_id", "abc_id"], name: "index_xyz_on_efg_id_and_abc_id", using: :btree
end

Till now, it seems to be nothing related to our code, if it turns out to be, I will report here.

Thanks!

[ankane]

Hey @ziaulrehman40, Strong Migrations is tested against Rails 5.1 (https://travis-ci.org/ankane/strong_migrations), so think something else in your app may be interfering with it.

[ankane]

@checker should be set on initialization, but maybe another gem is overriding it?

strong_migrations/lib/strong_migrations/migration.rb

Line 5 in b60e8e4

@checker = StrongMigrations::Checker.new(self)

[ziaulrehman40]

It was working fine on 4.2 and 5.0, i can check what else ot updated while migrating on 5.1.

Though nothing really stands out, but I updated haml-rails, pg and added listen gem.

Nothing else i can in my changelog. I can try reverting these gem updates/additions if that helps.

[ziaulrehman40]

No, didn't help. I undid all gemfile changes and still same.

[ankane]

The error doesn't occur in the test suite or a fresh Rails 5.1 app, so all signs point to something in your app.

[ziaulrehman40]

Yeah i understand that, but we must hunt it down whatever it is.
I will try to spend some time on this and as soon as I find something i will report.

Just to add,

1. StrongMigrations.start_after is set, and there are a few migrations that run just fine after this set timestamp value, and this specific one fails which is near end of the list(second last).

2. If i comment this specific migration's actual migration stuff, it passes over it just fine.

[ziaulrehman40]

Oh found it...

If you look closely, you can see there is no def change or def up in the migration i have pasted above, that was the issue. wrapping migration in a def change fixed it.

I am not sure how it was even working in older versions... this is confusing.

[ankane]

Migrations inherit from ActiveRecord::Schema, which can run operations without methods. Anyways, I updated the code to be more robust to this scenario.

[ziaulrehman40]

Thankyou @ankane , this approach was what came to my mind when i was investigating, but you were super fast to push a commit. 👍