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Merge pull request rails#51909 from rails/rm-release-notes
Draft of the release notes
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‎guides/source/7_2_release_notes.md

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@@ -5,6 +5,26 @@ Ruby on Rails 7.2 Release Notes
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Highlights in Rails 7.2:
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* Development containers configuration for applications.
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* Add browser version guard by default.
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* Make Ruby 3.1 the new minimum version.
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* Default Progressive Web Application (PWA) files.
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* Add omakase RuboCop rules by default.
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* Add GitHub CI workflow by default to new applications.
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* Add Brakeman by default to new applications.
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* Set a new default for the Puma thread count.
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* Prevent jobs from being scheduled within transactions.
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* Per transaction commit and rollback callbacks.
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* Enable YJIT by default if running Ruby 3.3+.
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* New design for the Rails guides.
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* Setup jemalloc in default Dockerfile to optimize memory allocation.
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* Suggest puma-dev configuration in bin/setup.
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These release notes cover only the major changes. To learn about various bug
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fixes and changes, please refer to the changelogs or check out the [list of
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commits](https://github.com/rails/rails/commits/7-2-stable) in the main Rails
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repository on GitHub.
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--------------------------------------------------------------------------------
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Upgrading to Rails 7.2
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Major Features
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--------------
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### Development containers configuration for applications
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A [development container](https://containers.dev/) (or dev container for short) allows you to use a container
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as a full-featured development environment.
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Rails 7.2 adds the ability to generate a development container configuration for your application. This configuration
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includes a `.devcontainer` folder with a `Dockerfile`, a `docker-compose.yml` file, and a `devcontainer.json` file.
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By default, the dev container contains the following:
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* A Redis container for use with Kredis, Action Cable, etc.
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* A database (SQLite, Postgres, MySQL or MariaDB)
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* A Headless Chrome container for system tests
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* Active Storage configured to use the local disk and with preview features working
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To generate a new application with a development container, you can run:
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```bash
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rails new myapp --devcontainer
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```
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For existing applications, a `devcontainer` command is now available:
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```bash
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rails devcontainer
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```
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For more information, see the [Getting Started with Dev Containers](https://edgeguides.rubyonrails.org/getting_started_with_devcontainer.html) guide.
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### Add browser version guard by default
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Rails now adds the ability to specify the browser versions that will be allowed to access all actions
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(or some, as limited by `only:` or `except:`).
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Only browsers matched in the hash or named set passed to `versions:` will be blocked if they're below the versions
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specified.
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This means that all other unknown browsers, as well as agents that aren't reporting a user-agent header, will be allowed access.
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A browser that's blocked will by default be served the file in `public/406-unsupported-browser.html` with a HTTP status
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code of "406 Not Acceptable".
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Examples:
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```ruby
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class ApplicationController < ActionController::Base
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# Allow only browsers natively supporting webp images, web push, badges, import maps, CSS nesting + :has
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allow_browser versions: :modern
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end
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class ApplicationController < ActionController::Base
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# All versions of Chrome and Opera will be allowed, but no versions of "internet explorer" (ie). Safari needs to be 16.4+ and Firefox 121+.
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allow_browser versions: { safari: 16.4, firefox: 121, ie: false }
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end
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class MessagesController < ApplicationController
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# In addition to the browsers blocked by ApplicationController, also block Opera below 104 and Chrome below 119 for the show action.
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allow_browser versions: { opera: 104, chrome: 119 }, only: :show
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end
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```
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Newly generated applications have this guard set in `ApplicationController`.
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For more information, see the [allow_browser](https://api.rubyonrails.org/classes/ActionController/AllowBrowser/ClassMethods.html#method-i-allow_browser)
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documentation.
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### Make Ruby 3.1 the new minimum version
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Until now, Rails only dropped compatibility with older Rubies on new majors version.
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We are changing this policy because it causes us to keep compatibility with long
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unsupported versions of Ruby or to bump the Rails major version more often, and to
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drop multiple Ruby versions at once when we bump the major.
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We will now drop Ruby versions that are end-of-life on minor Rails versions at the time of the release.
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For Rails 7.2, Ruby 3.1 is the new minimum version.
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### Default Progressive Web Application (PWA) files
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In preparation to better supporting the creation of PWA applications with Rails, we now generate default PWA files for the manifest
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and service worker, which are served from `app/views/pwa` and can be dynamically rendered through ERB. Those files
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are mounted explicitly at the root with default routes in the generated routes file.
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For more information, see the [pull request adding the feature](https://github.com/rails/rails/pull/50528).
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### Add omakase RuboCop rules by default
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Rails applications now come with [RuboCop](https://rubocop.org/) configured with a set of rules from [rubocop-rails-omakase](https://github.com/rails/rubocop-rails-omakase) by default.
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Ruby is a beautifully expressive language that not only tolerates many different dialects, but celebrates their
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diversity. It was never meant as a language to be written exclusively in a single style across all libraries,
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frameworks, or applications. If you or your team has developed a particular house style that brings you joy,
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you should cherish that.
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This collection of RuboCop styles is for those who haven't committed to any specific dialect already. Who would just
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like to have a reasonable starting point, and who will benefit from some default rules to at least start a consistent
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approach to Ruby styling.
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These specific rules aren't right or wrong, but merely represent the idiosyncratic aesthetic sensibilities of Rails'
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creator. Use them whole, use them as a starting point, use them as inspiration, or however you see fit.
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### Add GitHub CI workflow by default to new applications
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Rails now adds a default GitHub CI workflow file to new applications. This will get especially newcomers off to a good
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start with automated scanning, linting, and testing. We find that a natural continuation for the modern age of what
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we've done since the start with unit tests.
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It's of course true that GitHub Actions are a commercial cloud product for private repositories after you've used the
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free tokens. But given the relationship between GitHub and Rails, the overwhelming default nature of the platform for
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newcomers, and the value of teaching newcomers good CI habits, we find this to be an acceptable trade-off.
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### Add Brakeman by default to new applications
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[Brakeman](https://brakemanscanner.org/) is a great way to prevent common security vulnerabilities in Rails from going
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into production.
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New applications come with Brakeman installed and combined with the GitHub CI workflow, it will run automatically on
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every push.
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### Set a new default for the Puma thread count
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Rails changed the default number of threads in Puma from 5 to 3.
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Due to the nature of well-optimized Rails applications, with quick SQL queries and slow 3rd-party calls running via jobs,
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Ruby can spend a significant amount of time waiting for the Global VM Lock (GVL) to release when the thread count is too
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high, which is hurting latency (request response time).
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After careful consideration, investigation, and based on battle-tested experience from applications running in
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production, we decided that a default of 3 threads is a good balance between concurrency and performance.
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You can follow a very detailed discussion about this change in [the issue](https://github.com/rails/rails/issues/50450).
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### Prevent jobs from being scheduled within transactions
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A common mistake with Active Job is to enqueue jobs from inside a transaction, causing them to potentially be picked
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and ran by another process, before the transaction is committed, which result in various errors.
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```ruby
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Topic.transaction do
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topic = Topic.create
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NewTopicNotificationJob.perform_later(topic)
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end
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```
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Now Active Job will automatically defer the enqueuing to after the transaction is committed, and drop the job if the
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transaction is rolled back.
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Various queue implementations can chose to disable this behavior, and users can disable it, or force it on a per job
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basis:
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```ruby
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class NewTopicNotificationJob < ApplicationJob
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self.enqueue_after_transaction_commit = false
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end
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```
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### Per transaction commit and rollback callbacks
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This is now possible due to a new feature that allows registering transaction callbacks outside of a record.
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`ActiveRecord::Base.transaction` now yields an `ActiveRecord::Transaction` object, which allows registering callbacks
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on it.
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```ruby
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Article.transaction do |transaction|
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article.update(published: true)
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transaction.after_commit do
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PublishNotificationMailer.with(article: article).deliver_later
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end
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end
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```
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`ActiveRecord::Base.current_transaction` was also added to allow to register callbacks on it.
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```ruby
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Article.current_transaction.after_commit do
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PublishNotificationMailer.with(article: article).deliver_later
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end
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```
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And finally, `ActiveRecord.after_all_transactions_commit` was added, for code that may run either inside or outside a
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transaction and needs to perform work after the state changes have been properly persisted.
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```ruby
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def publish_article(article)
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article.update(published: true)
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ActiveRecord.after_all_transactions_commit do
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PublishNotificationMailer.with(article: article).deliver_later
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end
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end
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```
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See [#51474](https://github.com/rails/rails/pull/51474) and [#51426](https://github.com/rails/rails/pull/51426) for more information:
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### Enable YJIT by default if running Ruby 3.3+
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YJIT is Ruby's JIT compiler that is available in CRuby since Ruby 3.1. It can provide significant performance
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improvements for Rails applications, offering 15-25% latency improvements.
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In Rails 7.2, YJIT is enabled by default if running Ruby 3.3 or newer.
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You can disable YJIT by setting:
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```ruby
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Rails.application.config.yjit = false
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```
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### New design for the Rails guides
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When Rails 7.0 landed in December 2021, it came with a fresh new homepage and a new boot screen. The design of the
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guides, however, has remained largely untouched since 2009 - a point which hasn’t gone unnoticed (we heard your feedback).
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With all of the work right now going into removing complexity from the Rails framework and making the documentation
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consistent, clear, and up-to-date, it was time to tackle the design of the guides and make them equally modern, simple,
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and fresh.
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We worked with UX designer [John Athayde](https://meticulous.com/) to take the look and feel of the homepage and
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transfer that over to the Rails guides to make them clean, sleek, and up-to-date.
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The layout will remain the same, but from today you will see the following changes reflected in the guides:
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* Cleaner, less busy design.
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* Fonts, color scheme, and logo more consistent with the home page.
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* Updated iconography.
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* Simplified navigation.
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* Sticky "Chapters" navbar when scrolling.
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See the [announcement blog post for some before/after images](https://rubyonrails.org/2024/3/20/rails-guides-get-a-facelift).
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### Setup jemalloc in default Dockerfile to optimize memory allocation
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[Ruby's use of `malloc` can create memory fragmentation problems, especially when using multiple threads](https://www.speedshop.co/2017/12/04/malloc-doubles-ruby-memory.html)
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like Puma does. Switching to an allocator that uses different patterns to avoid fragmentation can decrease memory usage
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by a substantial margin.
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Rails 7.2 now includes [jemalloc](https://jemalloc.net/) in the default Dockerfile to optimize memory allocation.
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### Suggest puma-dev configuration in bin/setup
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[Puma-dev](https://github.com/puma/puma-dev) is the golden path for developing multiple Rails applications locally, if you're not using Docker.
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Rails now suggests how to get that setup in a new comment you'll find in `bin/setup`.
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Railties
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--------
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* Remove deprecated `find_cmd_and_exec` console helper.
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* Remove support for `oracle`, `sqlserver`, and JRuby specific database adapters from the rails new
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and rails db:system:change commands.
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* Remove support for `oracle`, `sqlserver`, and JRuby specific database adapters from the `new`
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and `db:system:change` `rails` commands.
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* Remove `config.public_file_server.enabled` option from the generators.
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### Deprecations
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### Notable changes
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* Add `RuboCop` with rules from [rubocop-rails-omakase](https://github.com/rails/rubocop-rails-omakase)
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* Add RuboCop with rules from [rubocop-rails-omakase](https://github.com/rails/rubocop-rails-omakase)
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by default in both new applications and plugins.
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* Add `Brakeman` with default configuration for security checks in new applications.
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* Add Brakeman with default configuration for security checks in new applications.
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* Add GitHub CI files for `Dependabot`, `Brakeman`, `RuboCop`, and running tests by default for new applications and plugins.
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* Add GitHub CI files for Dependabot, Brakeman, RuboCop, and running tests by default for new applications and plugins.
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* YJIT is now enabled by default for new applications running on Ruby 3.3+.
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* Introduce `Rails::Generators::Testing::Assertions#assert_initializer` to test initializers.
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* System tests now use headless Chrome by default for new applications.
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* System tests now use Headless Chrome by default for new applications.
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* Support the `BACKTRACE` environment variable to turn off backtrace cleaning in normal server runnings.
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Previously, this was only available for the testing.
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* Support the `BACKTRACE` environment variable to turn off backtrace cleaning in normal server runnings.
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Previously, this was only available for testing.
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* Add default Progressive Web App (PWA) files for the manifest and service worker, served from `app/views/pwa`,
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### Removals
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* Remove deprecated `@rails/ujs` in favor of `Turbo`.
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* Remove deprecated `@rails/ujs` in favor of Turbo.
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### Deprecations
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‎guides/source/documents.yaml

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name: Version 7.2 - ?
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url: 7_2_release_notes.html
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description: Release notes for Rails 7.2.
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work_in_progress: true
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-
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name: Version 7.1 - October 2023
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url: 7_1_release_notes.html

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