Foreign key to different table in migration does not reverse correctly

[lukeredpath]

Steps to reproduce

A new feature was introduced in response to #21563 which allows a different table to be specified in a references migration where the foreign key column does not match the table it is referencing.

For example, given two tables, "buildings" and "devices", where devices have a location association which is a building.

The AR class might be:

class Device < ApplicationRecord
  belongs_to :location, class_name: 'Building'
end

The location_id column can be added with a foreign key constraint using this new feature:

change_table(:devices) do |t|
  t.references :location, foreign_key: {to_table: :buildings}
end

This works as expected. In my schema I have:

add_foreign_key "devices", "buildings", column: "location_id"

However when I try to roll back this migration, it fails.

Expected behaviour

Rolling back should remove the location_id column from devices and the foreign key constraint.

Actual behaviour

The migration fails with the error:

== 20160527152008 AssociateDeviceWithBuilding: reverting ==============
-- remove_reference(:devices, :location, {:foreign_key=>{:to_table=>:buildings}})
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

Table 'devices' has no foreign key for locations
-e:1:in `<main>'
ArgumentError: Table 'client_devices' has no foreign key for locations

What the reverse migration should be doing is looking for a foreign key for buildings but it seems to be ignoring the to_table parameter on reverse.

System configuration

Rails version:
Rails 5 RC1

Ruby version:
ruby 2.2.3p173

[maclover7]

Can you collate your sample code above and create an executable test script using one of the templates here, that would demonstrate the problem you are seeing?

[lukeredpath]

Sure. I can't seem to reproduce it with sqlite, but I can with postgres which is the DB I'm using anyway. Executable test:

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', '>= 5.0.0.rc1', '< 5.1'
  gem 'pg'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

DB_NAME = 'test_25169'

system("dropdb #{DB_NAME}")
system("createdb #{DB_NAME}")

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'postgresql', database: DB_NAME)
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :buildings, force: true do |t|
  end

  create_table :devices, force: true do |t|
  end
end

class AssociateDeviceWithBuilding < ActiveRecord::Migration[5.0]
  def change
    change_table(:devices) do |t|
      t.references :location, foreign_key: {to_table: :buildings}
    end
  end
end

class BugTest < Minitest::Test
  def test_foreign_key_migration_is_reversible
    AssociateDeviceWithBuilding.migrate(:up)

    assert current_schema.match(/add_foreign_key "devices", "buildings", column: "location_id"/)

    # this should not raise
    AssociateDeviceWithBuilding.migrate(:down)

    refute current_schema.match(/add_foreign_key "devices", "buildings", column: "location_id"/)
  end

  private

  def current_schema
    output = StringIO.new
    ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, output)
    output.rewind
    output.read
  end
end

Output for me (backtrace omitted):

Finished in 0.027510s, 36.3503 runs/s, 36.3503 assertions/s.

  1) Error:
BugTest#test_association_stuff:
ArgumentError: Table 'devices' has no foreign key for locations