raises an error for models using enum.

[krisleech]

class Post < ActiveRecord::Base
  enum status: %i[draft published]
end

The error we get is:

Undeclared attribute type for enum 'status'. Enums must be backed by a database column or declared with an explicit type via `attribute`.

Here is a reproducible example:

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem 'pry'
  gem 'rspec'
  gem "activerecord", '7.1.2'
  gem 'activerecord-nulldb-adapter', '1.0.1', require: false
end

require "active_record"
require 'nulldb_rspec'
require "rspec/autorun"

schema = <<-SCHEMA
ActiveRecord::Schema[7.1].define do
  create_enum "post_status", ["draft", "published"]

  create_table "posts", force: :cascade do |t|
    t.enum "status", default: "draft", enum_type: "post_status"
  end
end
SCHEMA

schema_filename = File.join(__dir__, 'schema.rb')

File.write(schema_filename, schema)

ActiveRecord::Base.establish_connection(
  adapter: :nulldb,
  schema: schema_filename
)

require_relative 'schema'

class Post < ActiveRecord::Base
  enum status: %i[draft published]
end

RSpec.describe 'enum' do
  it 'has status column' do
    expect(Post.column_names).to include('status')
  end

  it 'does not raise an error' do
    expect { Post.new }.not_to raise_error
  end
end

The exception comes from ActiveRecord::Enum#_enum (gems/activerecord-7.1.2/lib/active_record/enum.rb:250).

attribute(name, **options) do |subtype|
    249:         binding.pry
 => 250:           if subtype == ActiveModel::Type.default_value
    251:             raise "Undeclared attribute type for enum '#{name}'. Enums must be" \
    252:               " backed by a database column or declared with an explicit type" \
    253:               " via `attribute`."
    254:           end

With NullDB subtype, in the above, is the same as ActiveModel::Type.default_value, thus the error:

pry> subtype
=> #<ActiveModel::Type::Value:0x00000001059d25a0 @limit=nil, @precision=nil, @scale=nil>
pry> ActiveModel::Type.default_value
=> #<ActiveModel::Type::Value:0x0000000105935070 @limit=nil, @precision=nil, @scale=nil>

With regular adapter they are different and thus no error:

pry> subtype
=> #<ActiveModel::Type::String:0x000000010c6f2a40 @false="f", @limit=nil, @precision=nil, @scale=nil, @true="t">
pry> ActiveModel::Type.default_value
=> #<ActiveModel::Type::Value:0x000000010bc38258 @limit=nil, @precision=nil, @scale=nil>

It's been great having unit tests use this gem. Any ideas greatly appreciated!

• nulldb 1.0.1
• ActiveRecord 7.1.2

[krisleech]

@Zeko369 I noticed your PR, did you come across this issue?