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Pull Requests

There are two fundamental components of the Pull Request process: one concrete and technical, and one more process oriented. The concrete and technical component involves the specific details of setting up your local environment so that you can make the actual changes. This is where we will start.

Dependencies

Node.js has several bundled dependencies in the deps/ and the tools/ directories that are not part of the project proper. Changes to files in those directories should be sent to their respective projects. Do not send a patch to Node.js. We cannot accept such patches.

In case of doubt, open an issue in the issue tracker or contact one of the project Collaborators. Node.js has two IRC channels: #Node.js for general help and questions, and #Node-dev for development of Node.js core specifically.

Setting up your local environment

To get started, you will need to have git installed locally. Depending on your operating system, there are also a number of other dependencies required. These are detailed in the Building guide.

Once you have git and are sure you have all of the necessary dependencies, it's time to create a fork.

Step 1: Fork

Fork the project on GitHub and clone your fork locally.

$ git clone git@github.com:username/node.git
$ cd node
$ git remote add upstream https://github.com/nodejs/node.git
$ git fetch upstream

It is recommended to configure git so that it knows who you are:

$ git config user.name "J. Random User"
$ git config user.email "j.random.user@example.com"

You can use any name/email address you prefer here. We only use the metadata generated by git using this configuration for properly attributing your changes to you in the AUTHORS file and the changelog.

If you would like for the Github UI to link the commit to your account and award you the Contributor label after the changes have been merged, make sure this local email is also added to your GitHub email list.

Step 2: Branch

As a best practice to keep your development environment as organized as possible, create local branches to work within. These should also be created directly off of the master branch.

$ git checkout -b my-branch -t upstream/master

The Process of Making Changes

Step 3: Code

The vast majority of Pull Requests opened against the nodejs/node repository includes changes to one or more of the following:

  • the C/C++ code contained in the src directory
  • the JavaScript code contained in the lib directory
  • the documentation in doc/api
  • tests within the test directory.

If you are modifying code, please be sure to run make lint from time to time to ensure that the changes follow the Node.js code style guide.

Any documentation you write (including code comments and API documentation) should follow the Style Guide. Code samples included in the API docs will also be checked when running make lint (or vcbuild.bat lint on Windows).

For contributing C++ code, you may want to look at the C++ Style Guide.

Step 4: Commit

It is a recommended best practice to keep your changes as logically grouped as possible within individual commits. There is no limit to the number of commits any single Pull Request may have, and many contributors find it easier to review changes that are split across multiple commits.

$ git add my/changed/files
$ git commit

Note that multiple commits often get squashed when they are landed (see the notes about commit squashing).

Commit message guidelines

A good commit message should describe what changed and why.

  1. The first line should:

    • contain a short description of the change (preferably 50 characters or less, and no more than 72 characters)
    • be entirely in lowercase with the exception of proper nouns, acronyms, and the words that refer to code, like function/variable names
    • be prefixed with the name of the changed subsystem and start with an imperative verb. Check the output of git log --oneline files/you/changed to find out what subsystems your changes touch.

    Examples:

    • net: add localAddress and localPort to Socket
    • src: fix typos in async_wrap.h
  2. Keep the second line blank.

  3. Wrap all other lines at 72 columns (except for long URLs).

  4. If your patch fixes an open issue, you can add a reference to it at the end of the log. Use the Fixes: prefix and the full issue URL. For other references use Refs:.

    Examples:

    • Fixes: https://github.com/nodejs/node/issues/1337
    • Refs: http://eslint.org/docs/rules/space-in-parens.html
    • Refs: https://github.com/nodejs/node/pull/3615
  5. If your commit introduces a breaking change (semver-major), it should contain an explanation about the reason of the breaking change, which situation would trigger the breaking change and what is the exact change.

Sample complete commit message:

subsystem: explain the commit in one line

Body of commit message is a few lines of text, explaining things
in more detail, possibly giving some background about the issue
being fixed, etc.

The body of the commit message can be several paragraphs, and
please do proper word-wrap and keep columns shorter than about
72 characters or so. That way, `git log` will show things
nicely even when it is indented.

Fixes: https://github.com/nodejs/node/issues/1337
Refs: http://eslint.org/docs/rules/space-in-parens.html

If you are new to contributing to Node.js, please try to do your best at conforming to these guidelines, but do not worry if you get something wrong. One of the existing contributors will help get things situated and the contributor landing the Pull Request will ensure that everything follows the project guidelines.

See core-validate-commit - A utility that ensures commits follow the commit formatting guidelines.

Step 5: Rebase

As a best practice, once you have committed your changes, it is a good idea to use git rebase (not git merge) to synchronize your work with the main repository.

$ git fetch upstream
$ git rebase upstream/master

This ensures that your working branch has the latest changes from nodejs/node master.

Step 6: Test

Bug fixes and features should always come with tests. A guide for writing tests in Node.js has been provided to make the process easier. Looking at other tests to see how they should be structured can also help.

The test directory within the nodejs/node repository is complex and it is often not clear where a new test file should go. When in doubt, add new tests to the test/parallel/ directory and the right location will be sorted out later.

Before submitting your changes in a Pull Request, always run the full Node.js test suite. To run the tests (including code linting) on Unix / macOS:

$ ./configure && make -j4 test

And on Windows:

> vcbuild test

(See the running tests section of Building guide for more details.)

Step 7: Push

Once you are sure your commits are ready to go, with passing tests and linting, begin the process of opening a Pull Request by pushing your working branch to your fork on GitHub.

$ git push origin my-branch

Step 8: Opening the Pull Request

From within GitHub, opening a new Pull Request will present you with a template that should be filled out:

<!--
Thank you for your Pull Request. Please provide a description above and review
the requirements below.

Bug fixes and new features should include tests and possibly benchmarks.

Contributors guide: https://github.com/nodejs/node/blob/master/CONTRIBUTING.md
-->

#### Checklist
<!-- Remove items that do not apply. For completed items, change [ ] to [x]. -->

- [ ] `make -j4 test` (UNIX), or `vcbuild test` (Windows) passes
- [ ] tests and/or benchmarks are included
- [ ] documentation is changed or added
- [ ] commit message follows [commit guidelines](https://github.com/nodejs/node/blob/master/doc/guides/contributing/pull-requests.md#commit-message-guidelines)

Please try to do your best at filling out the details, but feel free to skip parts if you're not sure what to put.

Once opened, Pull Requests are usually reviewed within a few days.

Step 9: Discuss and update

You will probably get feedback or requests for changes to your Pull Request. This is a big part of the submission process so don't be discouraged! Some contributors may sign off on the Pull Request right away, others may have more detailed comments or feedback. This is a necessary part of the process in order to evaluate whether the changes are correct and necessary.

To make changes to an existing Pull Request, make the changes to your local branch, add a new commit with those changes, and push those to your fork. GitHub will automatically update the Pull Request.

$ git add my/changed/files
$ git commit
$ git push origin my-branch

It is also frequently necessary to synchronize your Pull Request with other changes that have landed in master by using git rebase:

$ git fetch --all
$ git rebase origin/master
$ git push --force-with-lease origin my-branch

Important: The git push --force-with-lease command is one of the few ways to delete history in git. Before you use it, make sure you understand the risks. If in doubt, you can always ask for guidance in the Pull Request or on IRC in the #node-dev channel.

If you happen to make a mistake in any of your commits, do not worry. You can amend the last commit (for example if you want to change the commit log).

$ git add any/changed/files
$ git commit --amend
$ git push --force-with-lease origin my-branch

There are a number of more advanced mechanisms for managing commits using git rebase that can be used, but are beyond the scope of this guide.

Feel free to post a comment in the Pull Request to ping reviewers if you are awaiting an answer on something. If you encounter words or acronyms that seem unfamiliar, refer to this glossary.

Approval and Request Changes Workflow

All Pull Requests require "sign off" in order to land. Whenever a contributor reviews a Pull Request they may find specific details that they would like to see changed or fixed. These may be as simple as fixing a typo, or may involve substantive changes to the code you have written. While such requests are intended to be helpful, they may come across as abrupt or unhelpful, especially requests to change things that do not include concrete suggestions on how to change them.

Try not to be discouraged. If you feel that a particular review is unfair, say so, or contact one of the other contributors in the project and seek their input. Often such comments are the result of the reviewer having only taken a short amount of time to review and are not ill-intended. Such issues can often be resolved with a bit of patience. That said, reviewers should be expected to be helpful in their feedback, and feedback that is simply vague, dismissive and unhelpful is likely safe to ignore.

Step 10: Landing

In order to land, a Pull Request needs to be reviewed and approved by at least two Node.js Collaborators (one Collaborator approval is enough if the pull request has been open for more than 7 days) and pass a CI (Continuous Integration) test run. After that, as long as there are no objections from other contributors, the Pull Request can be merged. If you find your Pull Request waiting longer than you expect, see the notes about the waiting time.

When a collaborator lands your Pull Request, they will post a comment to the Pull Request page mentioning the commit(s) it landed as. GitHub often shows the Pull Request as Closed at this point, but don't worry. If you look at the branch you raised your Pull Request against (probably master), you should see a commit with your name on it. Congratulations and thanks for your contribution!

Reviewing Pull Requests

All Node.js contributors who choose to review and provide feedback on Pull Requests have a responsibility to both the project and the individual making the contribution. Reviews and feedback must be helpful, insightful, and geared towards improving the contribution as opposed to simply blocking it. If there are reasons why you feel the PR should not land, explain what those are. Do not expect to be able to block a Pull Request from advancing simply because you say "No" without giving an explanation. Be open to having your mind changed. Be open to working with the contributor to make the Pull Request better.

Reviews that are dismissive or disrespectful of the contributor or any other reviewers are strictly counter to the Code of Conduct.

When reviewing a Pull Request, the primary goals are for the codebase to improve and for the person submitting the request to succeed. Even if a Pull Request does not land, the submitters should come away from the experience feeling like their effort was not wasted or unappreciated. Every Pull Request from a new contributor is an opportunity to grow the community.

Review a bit at a time.

Do not overwhelm new contributors.

It is tempting to micro-optimize and make everything about relative performance, perfect grammar, or exact style matches. Do not succumb to that temptation.

Focus first on the most significant aspects of the change:

  1. Does this change make sense for Node.js?
  2. Does this change make Node.js better, even if only incrementally?
  3. Are there clear bugs or larger scale issues that need attending to?
  4. Is the commit message readable and correct? If it contains a breaking change is it clear enough?

When changes are necessary, request them, do not demand them, and do not assume that the submitter already knows how to add a test or run a benchmark.

Specific performance optimization techniques, coding styles and conventions change over time. The first impression you give to a new contributor never does.

Nits (requests for small changes that are not essential) are fine, but try to avoid stalling the Pull Request. Most nits can typically be fixed by the Node.js Collaborator landing the Pull Request but they can also be an opportunity for the contributor to learn a bit more about the project.

It is always good to clearly indicate nits when you comment: e.g. Nit: change foo() to bar(). But this is not blocking.

If your comments were addressed but were not folded automatically after new commits or if they proved to be mistaken, please, hide them with the appropriate reason to keep the conversation flow concise and relevant.

Be aware of the person behind the code

Be aware that how you communicate requests and reviews in your feedback can have a significant impact on the success of the Pull Request. Yes, we may land a particular change that makes Node.js better, but the individual might just not want to have anything to do with Node.js ever again. The goal is not just having good code.

Respect the minimum wait time for comments

There is a minimum waiting time which we try to respect for non-trivial changes, so that people who may have important input in such a distributed project are able to respond.

For non-trivial changes, Pull Requests must be left open for at least 48 hours. In most cases, when the PR is relatively small and focused on a narrow set of changes, that will provide more than enough time to adequately review. Sometimes changes take far longer to review, or need more specialized review from subject matter experts. When in doubt, do not rush.

Trivial changes, typically limited to small formatting changes or fixes to documentation, may be landed within the minimum 48 hour window.

Abandoned or Stalled Pull Requests

If a Pull Request appears to be abandoned or stalled, it is polite to first check with the contributor to see if they intend to continue the work before checking if they would mind if you took it over (especially if it just has nits left). When doing so, it is courteous to give the original contributor credit for the work they started (either by preserving their name and email address in the commit log, or by using an Author: meta-data tag in the commit.

Approving a change

Any Node.js core Collaborator (any GitHub user with commit rights in the nodejs/node repository) is authorized to approve any other contributor's work. Collaborators are not permitted to approve their own Pull Requests.

Collaborators indicate that they have reviewed and approve of the changes in a Pull Request either by using GitHub's Approval Workflow, which is preferred, or by leaving an LGTM ("Looks Good To Me") comment.

When explicitly using the "Changes requested" component of the GitHub Approval Workflow, show empathy. That is, do not be rude or abrupt with your feedback and offer concrete suggestions for improvement, if possible. If you're not sure how a particular change can be improved, say so.

Most importantly, after leaving such requests, it is courteous to make yourself available later to check whether your comments have been addressed.

If you see that requested changes have been made, you can clear another collaborator's Changes requested review.

Change requests that are vague, dismissive, or unconstructive may also be dismissed if requests for greater clarification go unanswered within a reasonable period of time.

If you do not believe that the Pull Request should land at all, use Changes requested to indicate that you are considering some of your comments to block the PR from landing. When doing so, explain why you believe the Pull Request should not land along with an explanation of what may be an acceptable alternative course, if any.

Accept that there are different opinions about what belongs in Node.js

Opinions on this vary, even among the members of the Technical Steering Committee.

One general rule of thumb is that if Node.js itself needs it (due to historic or functional reasons), then it belongs in Node.js. For instance, url parsing is in Node.js because of HTTP protocol support.

Also, functionality that either cannot be implemented outside of core in any reasonable way, or only with significant pain.

It is not uncommon for contributors to suggest new features they feel would make Node.js better. These may or may not make sense to add, but as with all changes, be courteous in how you communicate your stance on these. Comments that make the contributor feel like they should have "known better" or ridiculed for even trying run counter to the Code of Conduct.

Performance is not everything

Node.js has always optimized for speed of execution. If a particular change can be shown to make some part of Node.js faster, it's quite likely to be accepted. Claims that a particular Pull Request will make things faster will almost always be met by requests for performance benchmark results that demonstrate the improvement.

That said, performance is not the only factor to consider. Node.js also optimizes in favor of not breaking existing code in the ecosystem, and not changing working functional code just for the sake of changing.

If a particular Pull Request introduces a performance or functional regression, rather than simply rejecting the Pull Request, take the time to work with the contributor on improving the change. Offer feedback and advice on what would make the Pull Request acceptable, and do not assume that the contributor should already know how to do that. Be explicit in your feedback.

Continuous Integration Testing

All Pull Requests that contain changes to code must be run through continuous integration (CI) testing at https://ci.nodejs.org/.

Only Node.js core Collaborators with commit rights to the nodejs/node repository may start a CI testing run. The specific details of how to do this are included in the new Collaborator Onboarding guide.

Ideally, the code change will pass ("be green") on all platform configurations supported by Node.js (there are over 30 platform configurations currently). This means that all tests pass and there are no linting errors. In reality, however, it is not uncommon for the CI infrastructure itself to fail on specific platforms or for so-called "flaky" tests to fail ("be red"). It is vital to visually inspect the results of all failed ("red") tests to determine whether the failure was caused by the changes in the Pull Request.

Notes

Commit Squashing

In most cases, do not squash commits that you add to your Pull Request during the review process. When the commits in your Pull Request land, they may be squashed into one commit per logical change. Metadata will be added to the commit message (including links to the Pull Request, links to relevant issues, and the names of the reviewers). The commit history of your Pull Request, however, will stay intact on the Pull Request page.

For the size of "one logical change", 0b5191f can be a good example. It touches the implementation, the documentation, and the tests, but is still one logical change. All tests should always pass when each individual commit lands on the master branch.

Getting Approvals for Your Pull Request

A Pull Request is approved either by saying LGTM, which stands for "Looks Good To Me", or by using GitHub's Approve button. GitHub's Pull Request review feature can be used during the process. For more information, check out the video tutorial or the official documentation.

After you push new changes to your branch, you need to get approval for these new changes again, even if GitHub shows "Approved" because the reviewers have hit the buttons before.

CI Testing

Every Pull Request needs to be tested to make sure that it works on the platforms that Node.js supports. This is done by running the code through the CI system.

Only a Collaborator can start a CI run. Usually one of them will do it for you as approvals for the Pull Request come in. If not, you can ask a Collaborator to start a CI run.

Waiting Until the Pull Request Gets Landed

A Pull Request needs to stay open for at least 48 hours from when it is submitted, even after it gets approved and passes the CI. This is to make sure that everyone has a chance to weigh in. If the changes are trivial, collaborators may decide it doesn't need to wait. A Pull Request may well take longer to be merged in. All these precautions are important because Node.js is widely used, so don't be discouraged!

Check Out the Collaborator Guide

If you want to know more about the code review and the landing process, see the Collaborator Guide.