RecordNotUnique

ActiveRecord doesn't do a great job of rescuing ActiveRecord::RecordNotUnique exceptions arised from trying to insert a duplicate entry on a unique column.

This gem handles these scenarios and adds a validation error on the specified field, for each combination of fields that has a unique index attached to it, making it behave like a normal activerecord rollback. ! nethods like save! will continue to raise exceptions.

Even if you have validates_uniqueness_of :some_field in your model, it will prevent the ActiveRecord::RecordNotUnique from being raised in some cases, but not all, as race conditions between multiple processes could still attempt to insert duplicate entries to your table.

Installation

Add this line to your application's Gemfile:

gem 'record_not_unique'

And then execute:

$ bundle install

Usage

You'll need a database that supports unique constraints. This gem has been tested and works with MySQL(mysql2) and activerecord 3.2.22.x, 4.2.x, 6.x.

class AddIndexToUser < ActiveRecord::Migration
  def change
    add_index :users, :username, unique: true, name: "index_username_on_users"
  end
end

Before:

class User < ActiveRecord::Base
end

user = User.create(username: "foo")
dupe = User.create(username: "foo")
# => raises ActiveRecord::RecordNotUnique

After:

class User < ActiveRecord::Base
  handle_record_not_unique(field: ["username"], message: {username: :taken})
end

user = User.create(username: "foo")
dupe = User.create(username: "foo")
# => false
dupe.errors.full_messages
# => "Username has already been taken"

handle_record_not_unique supports multiple indices per model and procs for errors messages as well:

class User < ActiveRecord::Base
  handle_record_not_unique(
    {field: ["username"], message: {username: :taken} },
    {field: ["email"], message: {email: :taken} },
    {field: ["tenant_id", "secret"], message: {base: ->(user) { I18n.t('secret_failed_msg') } } }
  )
end

Note:

1. record_not_unique uses class variables to ensure the validations are passed on to child classes to avoid redundant definitions of handle_record_not_unique in multiple classes. If you want the error messages to be dynamic, you can use the Proc error handler and customize error messages for each class.

class User < ActiveRecord::Base
  handle_record_not_unique(field: ["username"], message: {username: ->(user) { user.custom_unique_message })

  # ...

  def custom_unique_message
    "Customer username has been taken"
  end
end

class AdminUser < User
  # ...
  
  def custom_unique_message
    "Admin username has been taken"
  end
end

2. We identified a peculiar behavior when using this with rails 4.2.x. When you are using an association to build the object and save it, a rollback on the associated object doesn't guarantee a rollback on the associatee's object. Even when using save! For instance:

class Tag < ActiveRecord::Base
  has_many :tag_uses
end

class TagUse < ActiveRecord::Base
  handle_record_not_unique(field: ["tag_id", "taggable_id", "taggable_type"], message: {base: "Tag is already associated to this entity!"})
  belongs_to :tag
  belongs_to :taggable, polymorphic: true
end

class User < ActiveRecord::Base
  has_many :tag_uses, as: :taggable
  has_many :tags, through: :tag_uses
end

irb:> user = User.new(name: some_name)
irb:> user.tag_uses.build(tag_id: some_tag.id)
irb:> user.save!

in case if the tag_uses entry is already present, the above does not rollback the whole transaction as one would expect. The user record will be persisted but the tag_uses entry will not be and the save! would return true. Peculiar, right?! there's a fix though: accepts_nested_attributes_for to the rescue.

class User < ActiveRecord::Base
  has_many :tag_uses, as: :taggable
  has_many :tags, through: :tag_uses

  accepts_nested_attributes_for :tag_uses
end

irb:> user = User.new(name: some_name, tag_uses_attributes: [{
  tag_id: some_tag.id
}])
irb:> user.save!

in this case, if the tag_uses entry is already present, both user and tag_uses records would be rolled back. Still, there will be no exceptions!!

When tested with rails 6, this raises an exception and a rollback as expected.

Todo

Add support for other database adapters.

Contributing

To run test cases,

bundle install
rake

License

This project is Licensed under the MIT License. Further details can be found here.