path: root/guides/source/6_0_release_notes.md

**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.**

Ruby on Rails 6.0 Release Notes
===============================

Highlights in Rails 6.0:

* Action Mailbox
* Action Text
* Parallel Testing
* Action Cable Testing

These release notes cover only the major changes. To learn about various bug
fixes and changes, please refer to the change logs or check out the [list of
commits](https://github.com/rails/rails/commits/6-0-stable) in the main Rails
repository on GitHub.

--------------------------------------------------------------------------------

Upgrading to Rails 6.0
----------------------

If you're upgrading an existing application, it's a great idea to have good test
coverage before going in. You should also first upgrade to Rails 5.2 in case you
haven't and make sure your application still runs as expected before attempting
an update to Rails 6.0. A list of things to watch out for when upgrading is
available in the
[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-5-2-to-rails-6-0)
guide.

Major Features
--------------

### Action Mailbox

[Pull Request](https://github.com/rails/rails/pull/34786)

[Action Mailbox](https://github.com/rails/rails/tree/6-0-stable/actionmailbox) allows you
to route incoming emails to controller-like mailboxes.
You can read more about Action Mailbox in the [Action Mailbox Basics](action_mailbox_basics.html) guide.

### Action Text

[Pull Request](https://github.com/rails/rails/pull/34873)

[Action Text](https://github.com/rails/rails/tree/6-0-stable/actiontext)
brings rich text content and editing to Rails. It includes
the [Trix editor](https://trix-editor.org) that handles everything from formatting
to links to quotes to lists to embedded images and galleries.
The rich text content generated by the Trix editor is saved in its own
RichText model that's associated with any existing Active Record model in the application.
Any embedded images (or other attachments) are automatically stored using
Active Storage and associated with the included RichText model.

You can read more about Action Text in the [Action Text Overview](action_text_overview.html) guide.

### Parallel Testing

[Pull Request](https://github.com/rails/rails/pull/31900)

[Parallel Testing](testing.html#parallel-testing) allows you to parallelize your
test suite. While forking processes is the default method, threading is
supported as well. Running tests in parallel reduces the time it takes
your entire test suite to run.

### Action Cable Testing

[Pull Request](https://github.com/rails/rails/pull/33659)

[Action Cable testing tools](testing.html#testing-action-cable) allow you to test your
Action Cable functionality at any level: connections, channels, broadcasts.

Railties
--------

Please refer to the [Changelog][railties] for detailed changes.

### Removals

*   Remove deprecated `after_bundle` helper inside plugins templates.
    ([Commit](https://github.com/rails/rails/commit/4d51efe24e461a2a3ed562787308484cd48370c7))

*   Remove deprecated support to `config.ru` that uses the application
    class as argument of `run`.
    ([Commit](https://github.com/rails/rails/commit/553b86fc751c751db504bcbe2d033eb2bb5b6a0b))

*   Remove deprecated `environment` argument from the rails commands.
    ([Commit](https://github.com/rails/rails/commit/e20589c9be09c7272d73492d4b0f7b24e5595571))

*   Remove deprecated `capify!` method in generators and templates.
    ([Commit](https://github.com/rails/rails/commit/9d39f81d512e0d16a27e2e864ea2dd0e8dc41b17))

*   Remove deprecated `config.secret_token`.
    ([Commit](https://github.com/rails/rails/commit/46ac5fe69a20d4539a15929fe48293e1809a26b0))

### Deprecations

*   Deprecate passing Rack server name as a regular argument to `rails server`.
    ([Pull Request](https://github.com/rails/rails/pull/32058))

*   Deprecate support for using `HOST` environment to specify server IP.
    ([Pull Request](https://github.com/rails/rails/pull/32540))

*   Deprecate accessing hashes returned by `config_for` by non-symbol keys.
    ([Pull Request](https://github.com/rails/rails/pull/35198))

### Notable changes

*   Add an explicit option `--using` or `-u` for specifying the server for the
    `rails server` command.
    ([Pull Request](https://github.com/rails/rails/pull/32058))

*   Add ability to see the output of `rails routes` in expanded format.
    ([Pull Request](https://github.com/rails/rails/pull/32130))

*   Run the seed database task using inline Active Job adapter.
    ([Pull Request](https://github.com/rails/rails/pull/34953))

*   Add a command `rails db:system:change` to change the database of the application.
    ([Pull Request](https://github.com/rails/rails/pull/34832))

*   Add `rails test:channels` command to test only Action Cable channels.
    ([Pull Request](https://github.com/rails/rails/pull/34947))

*   Introduce guard against DNS rebinding attacks.
    ([Pull Request](https://github.com/rails/rails/pull/33145))

*   Add ability to abort on failure while running generator commands.
    ([Pull Request](https://github.com/rails/rails/pull/34420))

*   Make Webpacker the default JavaScript compiler for Rails 6.
    ([Pull Request](https://github.com/rails/rails/pull/33079))

*   Add multiple database support for `rails db:migrate:status` command.
    ([Pull Request](https://github.com/rails/rails/pull/34137))

*   Add ability to use different migration paths from multiple databases in
    the generators.
    ([Pull Request](https://github.com/rails/rails/pull/34021))

*   Add support for multi environment credentials.
    ([Pull Request](https://github.com/rails/rails/pull/33521))

*   Make `null_store` as default cache store in test environment.
    ([Pull Request](https://github.com/rails/rails/pull/33773))

Action Cable
------------

Please refer to the [Changelog][action-cable] for detailed changes.

### Removals

### Deprecations

### Notable changes

*   The ActionCable javascript package has been converted from CoffeeScript
    to ES2015, and we now publish the source code in the npm distribution.

    This allows ActionCable users to depend on the javascript source code
    rather than the compiled code, which can produce smaller javascript bundles.

    This change includes some breaking changes to optional parts of the
    ActionCable javascript API:

    - Configuration of the WebSocket adapter and logger adapter have been moved
      from properties of `ActionCable` to properties of `ActionCable.adapters`.

    - The `ActionCable.startDebugging()` and `ActionCable.stopDebugging()`
      methods have been removed and replaced with the property
      `ActionCable.logger.enabled`.

Action Pack
-----------

Please refer to the [Changelog][action-pack] for detailed changes.

### Removals

### Deprecations

### Notable changes

Action View
-----------

Please refer to the [Changelog][action-view] for detailed changes.

### Removals

### Deprecations

### Notable changes

Action Mailer
-------------

Please refer to the [Changelog][action-mailer] for detailed changes.

### Removals

### Deprecations

### Notable changes

Active Record
-------------

Please refer to the [Changelog][active-record] for detailed changes.

### Removals

*   Remove deprecated `#set_state` from the transaction object.
    ([Commit](https://github.com/rails/rails/commit/6c745b0c5152a4437163a67707e02f4464493983))

*   Remove deprecated `#supports_statement_cache?` from the database adapters.
    ([Commit](https://github.com/rails/rails/commit/5f3ed8784383fb4eb0f9959f31a9c28a991b7553))

*   Remove deprecated `#insert_fixtures` from the database adapters.
    ([Commit](https://github.com/rails/rails/commit/400ba786e1d154448235f5f90183e48a1043eece))

*   Remove deprecated `ActiveRecord::ConnectionAdapters::SQLite3Adapter#valid_alter_table_type?`.
    ([Commit](https://github.com/rails/rails/commit/45b4d5f81f0c0ca72c18d0dea4a3a7b2ecc589bf))

*   Remove support for passing the column name to `sum` when a block is passed.
    ([Commit](https://github.com/rails/rails/commit/91ddb30083430622188d76eb9f29b78131df67f9))

*   Remove support for passing the column name to `count` when a block is passed.
    ([Commit](https://github.com/rails/rails/commit/67356f2034ab41305af7218f7c8b2fee2d614129))

*   Remove support for delegation of missing methods in a relation to arel.
    ([Commit](https://github.com/rails/rails/commit/d97980a16d76ad190042b4d8578109714e9c53d0))

*   Remove support for delegating missing methods in a relation to private methods of the class.
    ([Commit](https://github.com/rails/rails/commit/a7becf147afc85c354e5cfa519911a948d25fc4d))

*   Remove support for specifying a timestamp name for `#cache_key`.
    ([Commit](https://github.com/rails/rails/commit/0bef23e630f62e38f20b5ae1d1d5dbfb087050ea))

*   Remove deprecated `ActiveRecord::Migrator.migrations_path=`.
    ([Commit](https://github.com/rails/rails/commit/90d7842186591cae364fab3320b524e4d31a7d7d))

*   Remove deprecated `expand_hash_conditions_for_aggregates`.
    ([Commit](https://github.com/rails/rails/commit/27b252d6a85e300c7236d034d55ec8e44f57a83e))


### Deprecations

*   Deprecate mismatched case-sensitivity collation comparisons for uniqueness validator.
    ([Commit](https://github.com/rails/rails/commit/9def05385f1cfa41924bb93daa187615e88c95b9))

*   Deprecate using class level querying methods if the receiver scope has leaked.
    ([Pull Request](https://github.com/rails/rails/pull/35280))

*   Deprecate `config.activerecord.sqlite3.represent_boolean_as_integer`.
    ([Commit](https://github.com/rails/rails/commit/f59b08119bc0c01a00561d38279b124abc82561b))

*   Deprecate passing `migrations_paths` to `connection.assume_migrated_upto_version`.
    ([Commit](https://github.com/rails/rails/commit/c1b14aded27e063ead32fa911aa53163d7cfc21a))

*   Deprecate `ActiveRecord::Result#to_hash` in favor of `ActiveRecord::Result#to_a`.
    ([Commit](https://github.com/rails/rails/commit/16510d609c601aa7d466809f3073ec3313e08937))

*   Deprecate methods in `DatabaseLimits`: `column_name_length`, `table_name_length`,
    `columns_per_table`, `indexes_per_table`, `columns_per_multicolumn_index`,
    `sql_query_length`, and `joins_per_query`.
    ([Commit](https://github.com/rails/rails/commit/e0a1235f7df0fa193c7e299a5adee88db246b44f))

*   Deprecate `update_attributes`/`!` in favor of `update`/`!`.
    ([Commit](https://github.com/rails/rails/commit/5645149d3a27054450bd1130ff5715504638a5f5))

### Notable changes

*   Bump the minimum sqlite3 version to 1.4.
    ([Pull Request](https://github.com/rails/rails/pull/35844))

*   Add `rails db:prepare` to create a database if it doesn't exist, and run its migrations.
    ([Pull Request](https://github.com/rails/rails/pull/35768))

*   Add `after_save_commit` callback as shortcut for `after_commit :hook, on: [ :create, :update ]`.
    ([Pull Request](https://github.com/rails/rails/pull/35804))

*   Add `ActiveRecord::Relation#extract_associated` for extracting associated records from a relation.
    ([Pull Request](https://github.com/rails/rails/pull/35784))

*   Add `ActiveRecord::Relation#annotate` for adding SQL comments to ActiveRecord::Relation queries.
    ([Pull Request](https://github.com/rails/rails/pull/35617))

*   Add support for setting Optimizer Hints on databases.
    ([Pull Request](https://github.com/rails/rails/pull/35615))

*   Add `insert_all`/`insert_all!`/`upsert_all` methods for doing bulk inserts.
    ([Pull Request](https://github.com/rails/rails/pull/35631))

*   Add `rails db:seed:replant` that truncates tables of each database
    for ther current environment and loads the seeds.
    ([Pull Request](https://github.com/rails/rails/pull/34779))

*   Add `reselect` method, which is a short-hand for `unscope(:select).select(fields)`.
    ([Pull Request](https://github.com/rails/rails/pull/33611))

*   Add negative scopes for all enum values.
    ([Pull Request](https://github.com/rails/rails/pull/35381))

*   Add `#destroy_by` and `#delete_by` for conditional removals.
    ([Pull Request](https://github.com/rails/rails/pull/35316))

*   Add the ability to automatically switch database connections.
    ([Pull Request](https://github.com/rails/rails/pull/35073))

*   Add the ability to prevent writes to a database for the duration of a block.
    ([Pull Request](https://github.com/rails/rails/pull/34505))

*   Add an API for switching connections to support multiple databases.
    ([Pull Request](https://github.com/rails/rails/pull/34052))

*   Make timestamps with precision the default for migrations.
    ([Pull Request](https://github.com/rails/rails/pull/34970))

*   Support `:size` option to change text and blob size in MySQL.
    ([Pull Request](https://github.com/rails/rails/pull/35071))

*   Set both the foreign key and the foreign type columns to NULL for
    polymorphic associations on `dependent: :nullify` strategy.
    ([Pull Request](https://github.com/rails/rails/pull/28078))

*   Allow a permitted instance of `ActionController::Parameters` to be passed as an
    argument to `ActiveRecord::Relation#exists?`.
    ([Pull Request](https://github.com/rails/rails/pull/34891))

*   Add support in `#where` for endless ranges introduced in Ruby 2.6.
    ([Pull Request](https://github.com/rails/rails/pull/34906))

*   Make `ROW_FORMAT=DYNAMIC` a default create table option for MySQL.
    ([Pull Request](https://github.com/rails/rails/pull/34742))

*   Add the ability to disable scopes generated by `ActiveRecord.enum`.
    ([Pull Request](https://github.com/rails/rails/pull/34605/files))

*   Make implicit ordering configurable for a column.
    ([Pull Request](https://github.com/rails/rails/pull/34480))

*   Bump the minimum PostgreSQL version to 9.3, dropping support for 9.1 and 9.2.
    ([Pull Request](https://github.com/rails/rails/pull/34520))

*   Make the values of an enum frozen, raising an error when attempting to modify them.
    ([Pull Request](https://github.com/rails/rails/pull/34517))

*   Make the SQL of `ActiveRecord::StatementInvalid` errors its own error property
    and include SQL binds as a separate error property.
    ([Pull Request](https://github.com/rails/rails/pull/34468))

*   Add an `:if_not_exists` option to `create_table`.
    ([Pull Request](https://github.com/rails/rails/pull/31382))

*   Add support for multiple databases to `rails db:schema:cache:dump`
    and `rails db:schema:cache:clear`.
    ([Pull Request](https://github.com/rails/rails/pull/34181))

*   Add support for hash and url configs in database hash of `ActiveRecord::Base.connected_to`.
    ([Pull Request](https://github.com/rails/rails/pull/34196))

*   Add support for default expressions and expression indexes for MySQL.
    ([Pull Request](https://github.com/rails/rails/pull/34307))

*   Add an `index` option for `change_table` migration helpers.
    ([Pull Request](https://github.com/rails/rails/pull/23593))

*   Fix `transaction` reverting for migrations. Previously, commands inside of a `transaction`
    in a reverted migration ran uninverted. This change fixes that.
    ([Pull Request](https://github.com/rails/rails/pull/31604))

*   Allow `ActiveRecord::Base.configurations=` to be set with a symbolized hash.
    ([Pull Request](https://github.com/rails/rails/pull/33968))

*   Fix the counter cache to only update if the record is actually saved.
    ([Pull Request](https://github.com/rails/rails/pull/33913))

*   Add expression indexes support for the SQLite adapter.
    ([Pull Request](https://github.com/rails/rails/pull/33874))

*   Allow subclasses to redefine autosave callbacks for associated records.
    ([Pull Request](https://github.com/rails/rails/pull/33378))

*   Bump the minimum MySQL version to 5.5.8.
    ([Pull Request](https://github.com/rails/rails/pull/33853))

*   Use the utf8mb4 character set by default in MySQL.
    ([Pull Request](https://github.com/rails/rails/pull/33608))

*   Add the ability to filter out sensitive data in `#inspect`
    ([Pull Request](https://github.com/rails/rails/pull/33756), [Pull Request](https://github.com/rails/rails/pull/34208))

*   Change `ActiveRecord::Base.configurations` to return an object instead of a hash.
    ([Pull Request](https://github.com/rails/rails/pull/33637))

*   Add database configuration to disable advisory locks.
    ([Pull Request](https://github.com/rails/rails/pull/33691))

*   Update SQLite3 adapter `alter_table` method to restore foreign keys.
    ([Pull Request](https://github.com/rails/rails/pull/33585))

*   Allow the `:to_table` option of `remove_foreign_key` to be invertible.
    ([Pull Request](https://github.com/rails/rails/pull/33530))

*   Fix default value for mysql time types with specified precision.
    ([Pull Request](https://github.com/rails/rails/pull/33280))

*   Fix the `touch` option to behave consistently with `Persistence#touch` method.
    ([Pull Request](https://github.com/rails/rails/pull/33107))

*   Raise an exception for duplicate column definitions in Migrations.
    ([Pull Request](https://github.com/rails/rails/pull/33029))

*   Bump the minimum SQLite version to 3.8.
    ([Pull Request](https://github.com/rails/rails/pull/32923))

*   Fix parent records to not get saved with duplicate children records.
    ([Pull Request](https://github.com/rails/rails/pull/32952))

*   Ensure `Associations::CollectionAssociation#size` and `Associations::CollectionAssociation#empty?`
    use loaded association ids if present.
    ([Pull Request](https://github.com/rails/rails/pull/32617))

*   Add support to preload associations of polymorphic associations when not all the records have the requested associations.
    ([Commit](https://github.com/rails/rails/commit/75ef18c67c29b1b51314b6c8a963cee53394080b))

*   Add `touch_all` method to `ActiveRecord::Relation`.
    ([Pull Request](https://github.com/rails/rails/pull/31513))

*   Add `ActiveRecord::Base.base_class?` predicate.
    ([Pull Request](https://github.com/rails/rails/pull/32417))

*   Add custom prefix/suffix options to `ActiveRecord::Store.store_accessor`.
    ([Pull Request](https://github.com/rails/rails/pull/32306))

*   Add `ActiveRecord::Base.create_or_find_by`/`!` to deal with the SELECT/INSERT race condition in
    `ActiveRecord::Base.find_or_create_by`/`!` by leaning on unique constraints in the database.
    ([Pull Request](https://github.com/rails/rails/pull/31989))

*   Add `Relation#pick` as short-hand for single-value plucks.
    ([Pull Request](https://github.com/rails/rails/pull/31941))

Active Storage
--------------

Please refer to the [Changelog][active-storage] for detailed changes.

### Removals

### Deprecations

### Notable changes

Active Model
------------

Please refer to the [Changelog][active-model] for detailed changes.

### Removals

### Deprecations

### Notable changes

*   Add a configuration option to customize format of the `ActiveModel::Errors#full_message`.
    ([Pull Request](https://github.com/rails/rails/pull/32956))

*   Add support for configuring attribute name for `has_secure_password`.
    ([Pull Request](https://github.com/rails/rails/pull/26764))

*   Add `#slice!` method to `ActiveModel::Errors`.
    ([Pull Request](https://github.com/rails/rails/pull/34489))

*   Add `ActiveModel::Errors#of_kind?` to check presence of a specific error.
    ([Pull Request](https://github.com/rails/rails/pull/34866))

Active Support
--------------

Please refer to the [Changelog][active-support] for detailed changes.

### Removals

### Deprecations

### Notable changes

Active Job
----------

Please refer to the [Changelog][active-job] for detailed changes.

### Removals

*   Remove support for Qu gem.
    ([Pull Request](https://github.com/rails/rails/pull/32300))

### Deprecations

### Notable changes

*   Add support for custom serializers for Active Job arguments.
    ([Pull Request](https://github.com/rails/rails/pull/30941))

*   Add support for executing Active Jobs in the timezone in which
    they were enqueued.
    ([Pull Request](https://github.com/rails/rails/pull/32085))

*   Allow passing multiple exceptions to `retry_on`/`discard_on`.
    ([Commit](https://github.com/rails/rails/commit/3110caecbebdad7300daaf26bfdff39efda99e25))

*   Allow calling `assert_enqueued_with` and `assert_enqueued_email_with` without a block.
    ([Pull Request](https://github.com/rails/rails/pull/33258))

*   Wrap the notifications for `enqueue` and `enqueue_at` in the `around_enqueue`
    callback instead of `after_enqueue` callback.
    ([Pull Request](https://github.com/rails/rails/pull/33171))

*   Allow calling `perform_enqueued_jobs` without a block.
    ([Pull Request](https://github.com/rails/rails/pull/33626))

*   Allow calling `assert_performed_with` without a block.
    ([Pull Request](https://github.com/rails/rails/pull/33635))

*   Add `:queue` option to job assertions and helpers.
    ([Pull Request](https://github.com/rails/rails/pull/33635))

*   Add hooks to Active Job around retries and discards.
    ([Pull Request](https://github.com/rails/rails/pull/33751))

*   Add a way to test for subset of arguments when performing jobs.
    ([Pull Request](https://github.com/rails/rails/pull/33995))

*   Include deserialized arguments in jobs returned by Active Job
    test helpers.
    ([Pull Request](https://github.com/rails/rails/pull/34204))

*   Allow Active Job assertion helpers to accept Proc for `only`
    keyword.
    ([Pull Request](https://github.com/rails/rails/pull/34339))

*   Drop microseconds and nanoseconds from the job arguments in assertion helpers.
    ([Pull Request](https://github.com/rails/rails/pull/35713))

Ruby on Rails Guides
--------------------

Please refer to the [Changelog][guides] for detailed changes.

### Notable changes

Credits
-------

See the
[full list of contributors to Rails](https://contributors.rubyonrails.org/)
for the many people who spent many hours making Rails, the stable and robust
framework it is. Kudos to all of them.

[railties]:       https://github.com/rails/rails/blob/6-0-stable/railties/CHANGELOG.md
[action-pack]:    https://github.com/rails/rails/blob/6-0-stable/actionpack/CHANGELOG.md
[action-view]:    https://github.com/rails/rails/blob/6-0-stable/actionview/CHANGELOG.md
[action-mailer]:  https://github.com/rails/rails/blob/6-0-stable/actionmailer/CHANGELOG.md
[action-cable]:   https://github.com/rails/rails/blob/6-0-stable/actioncable/CHANGELOG.md
[active-record]:  https://github.com/rails/rails/blob/6-0-stable/activerecord/CHANGELOG.md
[active-storage]: https://github.com/rails/rails/blob/6-0-stable/activestorage/CHANGELOG.md
[active-model]:   https://github.com/rails/rails/blob/6-0-stable/activemodel/CHANGELOG.md
[active-support]: https://github.com/rails/rails/blob/6-0-stable/activesupport/CHANGELOG.md
[active-job]:     https://github.com/rails/rails/blob/6-0-stable/activejob/CHANGELOG.md
[guides]:         https://github.com/rails/rails/blob/6-0-stable/guides/CHANGELOG.md