v7.0.4
More at rubyonrails.org: More Ruby on Rails

Contributing to Ruby on Rails

This guide covers how you can become a part of the ongoing development of Ruby on Rails.

After reading this guide, you will know:

Ruby on Rails is not "someone else's framework". Over the years, thousands of people have contributed to Ruby on Rails ranging from a single character to massive architectural changes or significant documentation - all to make Ruby on Rails better for everyone. Even if you don't feel up to writing code or documentation yet, there are various other ways that you can contribute, from reporting issues to testing patches.

As mentioned in Rails' README, everyone interacting in Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Rails code of conduct.

1 Reporting an Issue

Ruby on Rails uses GitHub Issue Tracking to track issues (primarily bugs and contributions of new code). If you've found a bug in Ruby on Rails, this is the place to start. You'll need to create a (free) GitHub account to submit an issue, comment on issues, or create pull requests.

Bugs in the most recent released version of Ruby on Rails will likely get the most attention. Additionally, the Rails core team is always interested in feedback from those who can take the time to test edge Rails (the code for the version of Rails that is currently under development). Later in this guide, you'll find out how to get edge Rails for testing.

1.1 Creating a Bug Report

If you've found a problem in Ruby on Rails that is not a security risk, search the Issues on GitHub, in case it has already been reported. If you cannot find any open GitHub issues addressing the problem you found, your next step will be to open a new issue. (See the next section for reporting security issues.)

Your issue report should contain a title and a clear description of the issue at the bare minimum. You should include as much relevant information as possible and a code sample that demonstrates the issue. It would be even better to include a failing unit test that tests the expected behavior. Your goal should be to make it easy for yourself - and others - to reproduce the bug and figure out a fix.

Then, don't get your hopes up! Unless you have a "Code Red, Mission Critical, the World is Coming to an End" kind of bug, do not expect that the issue report will automatically see any activity or that someone will jump to fix it. You're creating this issue report so that other people with the same problem can confirm the bug and collaborate with you in fixing it.

1.2 Create an Executable Test Case

Having a way to reproduce your issue will help people confirm, investigate, and ultimately fix your issue. You can do this by providing an executable test case. To make this process easier, we have prepared several bug report templates for you to use as a starting point:

  • Template for Active Record (models, database) issues: gem / main
  • Template for testing Active Record (migration) issues: gem / main
  • Template for Action Pack (controllers, routing) issues: gem / main
  • Template for Active Job issues: gem / main
  • Template for Active Storage issues: gem / main
  • Template for Action Mailbox issues: gem / main
  • Generic template for other issues: gem / main

These templates include the boilerplate code to set up a test case against either a released version of Rails (*_gem.rb) or edge Rails (*_main.rb).

Copy the content of the appropriate template into a .rb file and make the necessary changes to demonstrate the issue. You can execute it by running ruby the_file.rb in your terminal. If all goes well, you should see your test case failing.

You can then share your executable test case as a gist or paste the content into the issue description.

1.3 Special Treatment for Security Issues

Please do not report security vulnerabilities with public GitHub issue reports. The Rails security policy page details the procedure to follow for security issues.

1.4 What about Feature Requests?

Please don't put "feature request" items into GitHub Issues. If there's a new feature that you want to see added to Ruby on Rails, you'll need to write the code yourself - or convince someone else to partner with you to write the code. Later in this guide, you'll find detailed instructions for proposing a patch to Ruby on Rails. If you enter a wish list item in GitHub Issues with no code, you can expect it to be marked "invalid" as soon as it's reviewed.

Sometimes, the line between 'bug' and 'feature' is a hard one to draw. Generally, a feature is anything that adds new behavior, while a bug is anything that causes incorrect behavior. Sometimes, the core team will have to make a judgment call. That said, the distinction generally determines which patch your change is released with; we love feature submissions! They just won't get backported to maintenance branches.

If you'd like feedback on an idea for a feature before doing the work to make a patch, please send an email to the rails-core mailing list. You might get no response, which means that everyone is indifferent. You might find someone who's also interested in building that feature. You might get a "This won't be accepted". But it's the proper place to discuss new ideas. GitHub Issues are not a particularly good venue for the sometimes long and involved discussions new features require.

2 Helping to Resolve Existing Issues

Beyond reporting issues, you can help the core team resolve existing ones by providing feedback about them. If you are new to Rails core development, that might be a great way to walk your first steps, you'll get familiar with the codebase and the processes.

If you check the issues list in GitHub Issues, you'll find lots of issues already requiring attention. What can you do about these? Quite a bit, actually:

2.1 Verifying Bug Reports

For starters, it helps just to verify bug reports. Can you reproduce the reported issue on your computer? If so, you can add a comment to the issue saying that you're seeing the same thing.

If an issue is very vague, can you help narrow it down to something more specific? Maybe you can provide additional information to reproduce the bug, or maybe you can eliminate unnecessary steps that aren't required to demonstrate the problem.

If you find a bug report without a test, it's very useful to contribute a failing test. This is also a great way to explore the source code: looking at the existing test files will teach you how to write more tests. New tests are best contributed in the form of a patch, as explained later on in the Contributing to the Rails Code section.

Anything you can do to make bug reports more succinct or easier to reproduce helps folks trying to write code to fix those bugs - whether you end up writing the code yourself or not.

2.2 Testing Patches

You can also help out by examining pull requests that have been submitted to Ruby on Rails via GitHub. In order to apply someone's changes, first create a dedicated branch:

$ git checkout -b testing_branch

Then, you can use their remote branch to update your codebase. For example, let's say the GitHub user JohnSmith has forked and pushed to a topic branch "orange" located at https://github.com/JohnSmith/rails.

$ git remote add JohnSmith https://github.com/JohnSmith/rails.git
$ git pull JohnSmith orange

After applying their branch, test it out! Here are some things to think about:

  • Does the change actually work?
  • Are you happy with the tests? Can you follow what they're testing? Are there any tests missing?
  • Does it have the proper documentation coverage? Should documentation elsewhere be updated?
  • Do you like the implementation? Can you think of a nicer or faster way to implement a part of their change?

Once you're happy that the pull request contains a good change, comment on the GitHub issue indicating your approval. Your comment should indicate that you like the change and what you like about it. Something like:

I like the way you've restructured that code in generate_finder_sql - much nicer. The tests look good too.

If your comment simply reads "+1", then odds are that other reviewers aren't going to take it too seriously. Show that you took the time to review the pull request.

3 Contributing to the Rails Documentation

Ruby on Rails has two main sets of documentation: the guides, which help you learn about Ruby on Rails, and the API, which serves as a reference.

You can help improve the Rails guides or the API reference by making them more coherent, consistent, or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails.

To do so, make changes to Rails guides source files (located here on GitHub) or RDoc comments in source code. Then open a pull request to apply your changes to the main branch.

When working with documentation, please take into account the API Documentation Guidelines and the Ruby on Rails Guides Guidelines.

4 Translating Rails Guides

We are happy to have people volunteer to translate the Rails guides. Just follow these steps:

  • Fork https://github.com/rails/rails.
  • Add a source folder for your language, for example: guides/source/it-IT for Italian.
  • Copy the contents of guides/source into your language directory and translate them.
  • Do NOT translate the HTML files, as they are automatically generated.

Note that translations are not submitted to the Rails repository; your work lives in your fork, as described above. This is because, in practice, documentation maintenance via patches is only sustainable in English.

To generate the guides in HTML format, you will need to install the guides dependencies, cd into the guides directory, and then run (e.g., for it-IT):

# only install gems necessary for the guides. To undo run: bundle config --delete without
$ bundle install --without job cable storage ujs test db
$ cd guides/
$ bundle exec rake guides:generate:html GUIDES_LANGUAGE=it-IT

This will generate the guides in an output directory.

The Redcarpet Gem doesn't work with JRuby.

Translation efforts we know about (various versions):

5 Contributing to the Rails Code

5.1 Setting Up a Development Environment

To move on from submitting bugs to helping resolve existing issues or contributing your own code to Ruby on Rails, you must be able to run its test suite. In this section of the guide, you'll learn how to set up the tests on your computer.

5.1.1 The Easiest Way

Start a GitHub Codespace from the repository and start developing right away from the browser IDE or in your local VScode. The Codespace is initialized with all required dependencies and allows you to run all tests.

5.1.2 The Easy Way

The easiest and recommended way to get a development environment ready to hack is to use the rails-dev-box.

5.1.3 The Hard Way

In case you can't use the Rails development box, see this other guide.

5.2 Clone the Rails Repository

To be able to contribute code, you need to clone the Rails repository:

$ git clone https://github.com/rails/rails.git

and create a dedicated branch:

$ cd rails
$ git checkout -b my_new_branch

It doesn't matter much what name you use because this branch will only exist on your local computer and your personal repository on GitHub. It won't be part of the Rails Git repository.

5.3 Bundle install

Install the required gems.

$ bundle install

5.4 Running an Application Against Your Local Branch

In case you need a dummy Rails app to test changes, the --dev flag of rails new generates an application that uses your local branch:

$ cd rails
$ bundle exec rails new ~/my-test-app --dev

The application generated in ~/my-test-app runs against your local branch and, in particular, sees any modifications upon server reboot.

For JavaScript packages, you can use yarn link to source your local branch in a generated application:

$ cd rails/activestorage
$ yarn link
$ cd ~/my-test-app
$ yarn link "@rails/activestorage"

5.5 Write Your Code

Now get busy and add/edit code. You're on your branch now, so you can write whatever you want (make sure you're on the right branch with git branch -a). But if you're planning to submit your change back for inclusion in Rails, keep a few things in mind:

  • Get the code right.
  • Use Rails idioms and helpers.
  • Include tests that fail without your code, and pass with it.
  • Update the (surrounding) documentation, examples elsewhere, and the guides: whatever is affected by your contribution.

Changes that are cosmetic and do not add anything substantial to the stability, functionality, or testability of Rails will generally not be accepted (read more about our rationales behind this decision).

5.5.1 Follow the Coding Conventions

Rails follows a simple set of coding style conventions:

  • Two spaces, no tabs (for indentation).
  • No trailing whitespace. Blank lines should not have any spaces.
  • Indent and no blank line after private/protected.
  • Use Ruby >= 1.9 syntax for hashes. Prefer { a: :b } over { :a => :b }.
  • Prefer &&/|| over and/or.
  • Prefer class << self over self.method for class methods.
  • Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
  • Use a = b and not a=b.
  • Use assert_not methods instead of refute.
  • Prefer method { do_stuff } instead of method{do_stuff} for single-line blocks.
  • Follow the conventions in the source you see used already.

The above are guidelines - please use your best judgment in using them.

Additionally, we have RuboCop rules defined to codify some of our coding conventions. You can run RuboCop locally against the file that you have modified before submitting a pull request:

$ bundle exec rubocop actionpack/lib/action_controller/metal/strong_parameters.rb
Inspecting 1 file
.

1 file inspected, no offenses detected

For rails-ujs CoffeeScript and JavaScript files, you can run npm run lint in actionview folder.

5.5.2 Spell Checking

We are running misspell which is mainly written in Golang to check spelling with GitHub Actions. Correct commonly misspelled English words quickly with misspell. misspell is different from most other spell checkers because it doesn't use a custom dictionary. You can run misspell locally against all files with:

find . -type f | xargs ./misspell -i 'aircrafts,devels,invertions' -error

Notable misspell help options or flags are:

  • -i string: ignore the following corrections, comma separated
  • -w: Overwrite file with corrections (default is just to display)

We also run codespell with GitHub Actions to check spelling and codespell runs against a small custom dictionary. codespell is written in Python and you can run it with:

codespell --ignore-words=codespell.txt

5.6 Benchmark Your Code

For changes that might have an impact on performance, please benchmark your code and measure the impact. Please share the benchmark script you used as well as the results. You should consider including this information in your commit message, to allow future contributors to easily verify your findings and determine if they are still relevant. (For example, future optimizations in the Ruby VM might render certain optimizations unnecessary.)

When optimizing for a specific scenario that you care about, it is easy to regress performance for other common cases. Therefore, you should test your change against a list of representative scenarios, ideally extracted from real-world production applications.

You can use the benchmark template as a starting point. It includes the boilerplate code to set up a benchmark using the benchmark-ips gem. The template is designed for testing relatively self-contained changes that can be inlined into the script.

5.7 Running Tests

It is not customary in Rails to run the full test suite before pushing changes. The railties test suite, in particular, takes a long time, and will take an especially long time if the source code is mounted in /vagrant as happens in the recommended workflow with the rails-dev-box.

As a compromise, test what your code obviously affects, and if the change is not in railties, run the whole test suite of the affected component. If all tests are passing, that's enough to propose your contribution. We have Buildkite as a safety net for catching unexpected breakages elsewhere.

5.7.1 Entire Rails:

To run all the tests, do:

$ cd rails
$ bundle exec rake test
5.7.2 For a Particular Component

You can run tests only for a particular component (e.g., Action Pack). For example, to run Action Mailer tests:

$ cd actionmailer
$ bin/test
5.7.3 For a Specific Directory

You can run tests only for a specific directory of a particular component (e.g., models in Active Storage). For example, to run tests in /activestorage/test/models:

$ cd activestorage
$ bin/test models
5.7.4 For a Specific File

You can run the tests for a particular file:

$ cd actionview
$ bin/test test/template/form_helper_test.rb
5.7.5 Running a Single Test

You can run a single test by name using the -n option:

$ cd actionmailer
$ bin/test test/mail_layout_test.rb -n test_explicit_class_layout
5.7.6 Running Tests with a Specific Seed

Test execution is randomized with a randomization seed. If you are experiencing random test failures, you can more accurately reproduce a failing test scenario by specifically setting the randomization seed.

Running all tests for a component:

$ cd actionmailer
$ SEED=15002 bin/test

Running a single test file:

$ cd actionmailer
$ SEED=15002 bin/test test/mail_layout_test.rb
5.7.7 Running Tests in Serial

Action Pack and Action View unit tests run in parallel by default. If you are experiencing random test failures, you can set the randomization seed and let these unit tests run in serial by setting PARALLEL_WORKERS=1

$ cd actionview
$ PARALLEL_WORKERS=1 SEED=53708 bin/test test/template/test_case_test.rb
5.7.8 Testing Active Record

First, create the databases you'll need. You can find a list of the required table names, usernames, and passwords in activerecord/test/config.example.yml.

For MySQL and PostgreSQL, it is sufficient to run:

$ cd activerecord
$ bundle exec rake db:mysql:build

Or:

$ cd activerecord
$ bundle exec rake db:postgresql:build

This is not necessary for SQLite3.

This is how you run the Active Record test suite only for SQLite3:

$ cd activerecord
$ bundle exec rake test:sqlite3

You can now run the tests as you did for sqlite3. The tasks are respectively:

$ bundle exec rake test:mysql2
$ bundle exec rake test:postgresql

Finally,

$ bundle exec rake test

will now run the three of them in turn.

You can also run any single test separately:

$ ARCONN=sqlite3 bundle exec ruby -Itest test/cases/associations/has_many_associations_test.rb

To run a single test against all adapters, use:

$ bundle exec rake TEST=test/cases/associations/has_many_associations_test.rb

You can invoke test_jdbcmysql, test_jdbcsqlite3 or test_jdbcpostgresql also. See the file activerecord/RUNNING_UNIT_TESTS.rdoc for information on running more targeted database tests.

5.8 Warnings

The test suite runs with warnings enabled. Ideally, Ruby on Rails should issue no warnings, but there may be a few, as well as some from third-party libraries. Please ignore (or fix!) them, if any, and submit patches that do not issue new warnings.

5.9 Updating the Documentation

The Ruby on Rails guides provide a high-level overview of Rails' features, while the API documentation delves into specifics.

If your PR adds a new feature, or changes how an existing feature behaves, check the relevant documentation, and update it or add to it as necessary.

For example, if you modify Active Storage's image analyzer to add a new metadata field, you should update the Analyzing Files section of the Active Storage guide to reflect that.

5.10 Updating the CHANGELOG

The CHANGELOG is an important part of every release. It keeps the list of changes for every Rails version.

You should add an entry to the top of the CHANGELOG of the framework you modified if you're adding or removing a feature, committing a bug fix, or adding deprecation notices. Refactorings and documentation changes generally should not go to the CHANGELOG.

A CHANGELOG entry should summarize what was changed and should end with the author's name. You can use multiple lines if you need more space, and you can attach code examples indented with 4 spaces. If a change is related to a specific issue, you should attach the issue's number. Here is an example CHANGELOG entry:

*   Summary of a change that briefly describes what was changed. You can use multiple
    lines and wrap them at around 80 characters. Code examples are ok, too, if needed:

        class Foo
          def bar
            puts 'baz'
          end
        end

    You can continue after the code example, and you can attach the issue number.

    Fixes #1234.

    *Your Name*

Your name can be added directly after the last word if there are no code examples or multiple paragraphs. Otherwise, it's best to make a new paragraph.

5.11 Ignoring Files Created by Your Editor / IDE

Some editors and IDEs will create hidden files or folders inside the rails folder. Instead of manually excluding those from each commit or adding them to Rails' .gitignore, you should add them to your own global gitignore file.

5.12 Updating the Gemfile.lock

Some changes require dependency upgrades. In these cases, make sure you run bundle update to get the correct version of the dependency and commit the Gemfile.lock file within your changes.

5.13 Commit Your Changes

When you're happy with the code on your computer, you need to commit the changes to Git:

$ git commit -a

This should fire up your editor to write a commit message. When you have finished, save, and close to continue.

A well-formatted and descriptive commit message is very helpful to others for understanding why the change was made, so please take the time to write it.

A good commit message looks like this:

Short summary (ideally 50 characters or less)

More detailed description, if necessary. Each line should wrap at
72 characters. Try to be as descriptive as you can. Even if you
think that the commit content is obvious, it may not be obvious
to others. Add any description that is already present in the
relevant issues; it should not be necessary to visit a webpage
to check the history.

The description section can have multiple paragraphs.

Code examples can be embedded by indenting them with 4 spaces:

    class ArticlesController
      def index
        render json: Article.limit(10)
      end
    end

You can also add bullet points:

- make a bullet point by starting a line with either a dash (-)
  or an asterisk (*)

- wrap lines at 72 characters, and indent any additional lines
  with 2 spaces for readability

Please squash your commits into a single commit when appropriate. This simplifies future cherry picks and keeps the git log clean.

5.14 Update Your Branch

It's pretty likely that other changes to main have happened while you were working. Go get them:

$ git checkout main
$ git pull --rebase

Now reapply your patch on top of the latest changes:

$ git checkout my_new_branch
$ git rebase main

No conflicts? Tests still pass? Change still seems reasonable to you? Then move on.

5.15 Fork

Navigate to the Rails GitHub repository and press "Fork" in the upper right-hand corner.

Add the new remote to your local repository on your local machine:

$ git remote add fork https://github.com/<your username>/rails.git

You may have cloned your local repository from rails/rails, or you may have cloned from your forked repository. The following git commands assume that you have made a "rails" remote that points to rails/rails.

$ git remote add rails https://github.com/rails/rails.git

Download new commits and branches from the official repository:

$ git fetch rails

Merge the new content:

$ git checkout main
$ git rebase rails/main
$ git checkout my_new_branch
$ git rebase rails/main

Update your fork:

$ git push fork main
$ git push fork my_new_branch

5.16 Issue a Pull Request

Navigate to the Rails repository you just pushed to (e.g. https://github.com/your-user-name/rails) and click on "Pull Requests" in the top bar (just above the code). On the next page, click "New pull request" in the upper right-hand corner.

The pull request should target the base repository rails/rails and the branch main. The head repository will be your work (your-user-name/rails), and the branch will be whatever name you gave your branch. Click "create pull request" when you're ready.

Ensure the changesets you introduced are included. Fill in some details about your potential patch, using the pull request template provided. When finished, click "Create pull request". The Rails core team will be notified about your submission.

5.17 Get some Feedback

Most pull requests will go through a few iterations before they get merged. Different contributors will sometimes have different opinions, and often patches will need to be revised before they can get merged.

Some contributors to Rails have email notifications from GitHub turned on, but others do not. Furthermore, (almost) everyone who works on Rails is a volunteer, and so it may take a few days for you to get your first feedback on a pull request. Don't despair! Sometimes it's quick; sometimes it's slow. Such is the open source life.

If it's been over a week, and you haven't heard anything, you might want to try and nudge things along. You can use the rubyonrails-core mailing list for this. You can also leave another comment on the pull request.

While you're waiting for feedback on your pull request, open up a few other pull requests and give someone else some! They'll appreciate it in the same way that you appreciate feedback on your patches.

Note that your pull request may be marked as "Approved" by somebody who does not have access to merge it. Further changes may still be required before members of the core or committer teams accept it. To prevent confusion, when giving feedback on someone else's pull request, please avoid marking it as "Approved."

5.18 Iterate as Necessary

It's entirely possible that the feedback you get will suggest changes. Don't get discouraged: the whole point of contributing to an active open source project is to tap into the community's knowledge. If people encourage you to tweak your code, then it's worth making the tweaks and resubmitting. If the feedback is that your code doesn't belong in the core, you might still think about releasing it as a gem.

5.18.1 Squashing Commits

One of the things that we may ask you to do is to "squash your commits", which will combine all of your commits into a single commit. We prefer pull requests that are a single commit. This makes it easier to backport changes to stable branches, squashing makes it easier to revert bad commits, and the git history can be a bit easier to follow. Rails is a large project, and a bunch of extraneous commits can add a lot of noise.

$ git fetch rails
$ git checkout my_new_branch
$ git rebase -i rails/main

< Choose 'squash' for all of your commits except the first one. >
< Edit the commit message to make sense, and describe all your changes. >

$ git push fork my_new_branch --force-with-lease

You should be able to refresh the pull request on GitHub and see that it has been updated.

5.18.2 Updating a Pull Request

Sometimes you will be asked to make some changes to the code you have already committed. This can include amending existing commits. In this case Git will not allow you to push the changes as the pushed branch and local branch do not match. Instead of opening a new pull request, you can force push to your branch on GitHub as described earlier in squashing commits section:

$ git push fork my_new_branch --force-with-lease

This will update the branch and pull request on GitHub with your new code. By force pushing with --force-with-lease, git will more safely update the remote than with a typical -f, which can delete work from the remote that you don't already have.

5.19 Older Versions of Ruby on Rails

If you want to add a fix to older versions of Ruby on Rails, you'll need to set up and switch to your own local tracking branch. Here is an example to switch to the 4-0-stable branch:

$ git branch --track 4-0-stable rails/4-0-stable
$ git checkout 4-0-stable

You may want to put your Git branch name in your shell prompt to make it easier to remember which version of the code you're working with.

Before working on older versions, please check the maintenance policy.

5.19.1 Backporting

Changes that are merged into main are intended for the next major release of Rails. Sometimes, it might be beneficial to propagate your changes back to older stable branches for inclusion in maintenance releases. Generally, security fixes and bug fixes are good candidates for a backport, while new features and patches that change expected behavior will not be accepted. When in doubt, it is best to consult a Rails team member before backporting your changes to avoid wasted effort.

For simple fixes, the easiest way to backport your changes is to extract a diff from your changes in main and apply them to the target branch.

First, make sure your changes are the only difference between your current branch and main:

$ git log main..HEAD

Then extract the diff:

$ git format-patch main --stdout > ~/my_changes.patch

Switch over to the target branch and apply your changes:

$ git checkout -b my_backport_branch 4-2-stable
$ git apply ~/my_changes.patch

This works well for simple changes. However, if your changes are complicated or if the code in main has deviated significantly from your target branch, it might require more work on your part. The difficulty of a backport varies greatly from case to case, and sometimes it is simply not worth the effort.

Once you have resolved all conflicts and made sure all the tests are passing, push your changes and open a separate pull request for your backport. It is also worth noting that older branches might have a different set of build targets than main. When possible, it is best to first test your backport locally against the oldest Ruby version permitted by the target branch's rails.gemspec before submitting your pull request.

And then... think about your next contribution!

6 Rails Contributors

All contributions get credit in Rails Contributors.

Feedback

You're encouraged to help improve the quality of this guide.

Please contribute if you see any typos or factual errors. To get started, you can read our documentation contributions section.

You may also find incomplete content or stuff that is not up to date. Please do add any missing documentation for main. Make sure to check Edge Guides first to verify if the issues are already fixed or not on the main branch. Check the Ruby on Rails Guides Guidelines for style and conventions.

If for whatever reason you spot something to fix but cannot patch it yourself, please open an issue.

And last but not least, any kind of discussion regarding Ruby on Rails documentation is very welcome on the official Ruby on Rails Forum.