Node.js Collaborator Guide

Issues and Pull Requests

Mind these guidelines, the opinions of other Collaborators, and guidance of the TSC. Notify other qualified parties for more input on an issue or a pull request. See Who to CC in the issue tracker.

Welcoming First-Time Contributors

Always show courtesy to individuals submitting issues and pull requests. Be welcoming to first-time contributors, identified by the GitHub badge.

For first-time contributors, check if the commit author is the same as the pull request author. This way, once their pull request lands, GitHub will show them as a Contributor. Ask if they have configured their git username and email to their liking.

Closing Issues and Pull Requests

Collaborators may close any issue or pull request that is not relevant to the future of the Node.js project. Where this is unclear, leave the issue or pull request open for several days to allow for discussion. Where this does not yield evidence that the issue or pull request has relevance, close it. Remember that issues and pull requests can always be re-opened if necessary.

Author ready pull requests

A pull request is author ready when:

There is a CI run in progress or completed.
There is at least one Collaborator approval.
There are no outstanding review comments.

Please always add the author ready label to the pull request in that case. Please always remove it again as soon as the conditions are not met anymore.

Handling own pull requests

When you open a pull request, start a CI right away and post the link to it in a comment in the pull request. Later, after new code changes or rebasing, start a new CI.

As soon as the pull request is ready to land, please do so. This allows other Collaborators to focus on other pull requests. If your pull request is not ready to land but is author ready, add the author ready label. If you wish to land the pull request yourself, use the "assign yourself" link to self-assign it.

Accepting Modifications

Contributors propose modifications to Node.js using GitHub pull requests. This includes modifications proposed by TSC members and other Collaborators. A pull request must pass code review and CI before landing into the codebase.

Code Reviews

At least two Collaborators must approve a pull request before the pull request lands. One Collaborator approval is enough if the pull request has been open for more than seven days.

Approving a pull request indicates that the Collaborator accepts responsibility for the change.

Approval must be from Collaborators who are not authors of the change.

In some cases, it may be necessary to summon a GitHub team to a pull request for review by @-mention. See Who to CC in the issue tracker.

If you are the first Collaborator to approve a pull request that has no CI yet, please start one. Post the link to the CI in the PR. Please also start a new CI if the PR creator pushed new code since the last CI run.

Consensus Seeking

If there are no objecting Collaborators, a pull request may land if it has the needed approvals, CI, and wait time. If a pull request meets all requirements except the wait time, please add the author ready label.

Where there is disagreement among Collaborators, consensus should be sought if possible. If reaching consensus is not possible, a Collaborator may escalate the issue to the TSC.

Collaborators should not block a pull request without providing a reason. Another Collaborator may ask an objecting Collaborator to explain their objection. If the objector is unresponsive, another Collaborator may dismiss the objection.

Breaking changes must receive TSC review. If two TSC members approve the pull request and no Collaborators object, then it may land. If there are objections, a Collaborator may apply the tsc-agenda label. That will put the pull request on the TSC meeting agenda.

Helpful resources

How to Do Code Reviews Like a Human (Part One)
How to Do Code Reviews Like a Human (Part Two)
Code Review Etiquette

Waiting for Approvals

Before landing pull requests, allow 48 hours for input from other Collaborators. Certain types of pull requests can be fast-tracked and may land after a shorter delay. For example:

Focused changes that affect only documentation and/or the test suite:
- code-and-learn tasks often fall into this category.
- good-first-issue pull requests may also be suitable.
Changes that fix regressions:
- Regressions that break the workflow (red CI or broken compilation).
- Regressions that happen right before a release, or reported soon after.

To propose fast-tracking a pull request, apply the fast-track label. Then add a comment that Collaborators may upvote.

If someone disagrees with the fast-tracking request, remove the label. Do not fast-track the pull request in that case.

The pull request may be fast-tracked if two Collaborators approve the fast-tracking request. To land, the pull request itself still needs two Collaborator approvals and a passing CI.

Collaborators may request fast-tracking of pull requests they did not author. In that case only, the request itself is also one fast-track approval. Upvote the comment anyway to avoid any doubt.

Testing and CI

All fixes must have a test case which demonstrates the defect. The test should fail before the change, and pass after the change.

All pull requests must pass continuous integration tests on the project CI server.

Do not land any pull requests without passing (green or yellow) CI runs. If there are CI failures unrelated to the change in the pull request, try "Resume Build". It is in the left navigation of the relevant node-test-pull-request job. It will preserve all the green results from the current job but re-run everything else.

Useful CI Jobs

node-test-pull-request is the CI job to test pull requests. It runs the build-ci and test-ci targets on all supported platforms.
node-test-pull-request-lite-pipeline runs the linter job. It also runs the tests on a very fast host. This is useful for changes that only affect comments or documentation.
citgm-smoker uses CitGM to allow you to run npm install && npm test on a large selection of common modules. This is useful to check whether a change will cause breakage in the ecosystem. To test Node.js ABI changes you can run citgm-abi-smoker.
node-stress-single-test can run a group of tests over and over on a specific platform. Use it to check that the tests are reliable.
node-test-commit-v8-linux runs the standard V8 tests. Run it when updating V8 in Node.js or floating new patches on V8.
node-test-commit-custom-suites enables customization of test suites and parameters. It can execute test suites not used in other CI test runs (such as tests in the internet or pummel directories). It can also make sure tests pass when provided with a flag not used in other CI test runs (such as --worker).

Internal vs. Public API

All functionality in the official Node.js documentation is part of the public API. Any undocumented object, property, method, argument, behavior, or event is internal. There are exceptions to this rule. Node.js users have come to rely on some undocumented behaviors. Collaborators treat many of those undocumented behaviors as public.

All undocumented functionality exposed via process.binding(...) is internal.

All undocumented functionality in lib/internal/**/*.js is internal. It is public, though, if it is re-exported by code in lib/*.js.

Non-exported Symbol properties and methods are internal.

Any undocumented object property or method that begins with _ is internal.

Any native C/C++ APIs/ABIs requiring the NODE_WANT_INTERNALS flag are internal.

Sometimes, there is disagreement about whether functionality is internal or public. In those cases, the TSC makes a determination.

For undocumented APIs that are public, open a pull request documenting the API.

Breaking Changes

At least two TSC members must approve backward-incompatible changes to the master branch.

Examples of breaking changes include:

removal or redefinition of existing API arguments
changing return values
removing or modifying existing properties on an options argument
adding or removing errors
altering expected timing of an event
changing the side effects of using a particular API

Breaking Changes and Deprecations

Existing stable public APIs that change in a backward-incompatible way must undergo deprecation. The exceptions to this rule are:

Adding or removing errors thrown or reported by a public API;
Changing error messages for errors without error code;
Altering the timing and non-internal side effects of the public API;
Changes to errors thrown by dependencies of Node.js, such as V8;
One-time exceptions granted by the TSC.

For more information, see Deprecations.

Breaking Changes to Internal Elements

Breaking changes to internal elements may occur in semver-patch or semver-minor commits. Take significant care when making and reviewing such changes. Make an effort to determine the potential impact of the change in the ecosystem. Use Canary in the Goldmine to test such changes. If a change will cause ecosystem breakage, then it is semver-major. Consider providing a Public API in such cases.

Unintended Breaking Changes

Sometimes, a change intended to be non-breaking turns out to be a breaking change. If such a change lands on the master branch, a Collaborator may revert it. As an alternative to reverting, the TSC may apply the semver-major label after-the-fact.

Reverting commits

Revert commits with git revert <HASH> or git revert <FROM>..<TO>. The generated commit message will not have a subsystem and may violate line length rules. That is OK. Append the reason for the revert and any Refs or Fixes metadata. Raise a Pull Request like any other change.

Introducing New Modules

Treat commits that introduce new core modules with extra care.

Check if the module's name conflicts with an existing ecosystem module. If it does, choose a different name unless the module owner has agreed in writing to transfer it.

If the new module name is free, register a placeholder in the module registry as soon as possible. Link to the pull request that introduces the new core module in the placeholder's README.

For pull requests introducing new core modules:

Allow at least one week for review.
Land only after sign-off from at least two TSC members.
Land with a Stability Index of Experimental. The module must remain Experimental until a semver-major release.

Additions to N-API

N-API provides an ABI-stable API guaranteed for future Node.js versions. N-API additions call for unusual care and scrutiny. If a change adds to node_api.h or node_api_types.h, consult the relevant guide.

Deprecations

Node.js uses three Deprecation levels. For all deprecated APIs, the API documentation must state the deprecation status.

Documentation-Only Deprecation
- A deprecation notice appears in the API documentation.
- There are no functional changes.
- By default, there will be no warnings emitted for such deprecations at runtime.
- May cause a runtime warning with the --pending-deprecation flag or NODE_PENDING_DEPRECATION environment variable.
Runtime Deprecation
- Emits a warning at runtime on first use of the deprecated API.
- If used with the --throw-deprecation flag, will throw a runtime error.
End-of-Life
- The API is no longer subject to the semantic versioning rules.
- Backward-incompatible changes including complete removal of such APIs may occur at any time.

Apply the notable change label to all pull requests that introduce Documentation-Only Deprecations. Such deprecations have no impact on code execution. Thus, they are not breaking changes (semver-major).

Runtime Deprecations and End-of-Life APIs (internal or public) are breaking changes (semver-major). The TSC may make exceptions, deciding that one of these deprecations is not a breaking change.

All deprecations receive a unique and immutable identifier. Documentation, warnings, and errors use the identifier when referring to the deprecation. The documentation for the deprecation identifier must always remain in the API documentation. This is true even if the deprecation is no longer in use (for example, due to removal of an End-of-Life deprecated API).

A deprecation cycle is a major release during which an API has been in one of the three Deprecation levels. Documentation-Only Deprecations may land in a minor release. They may not change to a Runtime Deprecation until the next major release.

No API can change to End-of-Life without going through a Runtime Deprecation cycle. There is no rule that deprecated code must progress to End-of-Life. Documentation-Only and Runtime Deprecations may remain in place for an unlimited duration.

Communicate pending deprecations and associated mitigations with the ecosystem as soon as possible. If possible, do it before the pull request adding the deprecation lands on the master branch.

Use the notable-change label on pull requests that add or change the deprecation level of an API.

Involving the TSC

Collaborators may opt to elevate pull requests or issues to the TSC. Do this if a pull request or issue:

is labeled semver-major, or
has a significant impact on the codebase, or
is controversial, or
is at an impasse among Collaborators who are participating in the discussion.

@-mention the @nodejs/tsc GitHub team if you want to elevate an issue to the TSC. Do not use the GitHub UI on the right-hand side to assign to @nodejs/tsc or request a review from @nodejs/tsc.

The TSC should serve as the final arbiter where required.

Landing Pull Requests

Avoid landing pull requests that have someone else as an assignee. Authors who wish to land their own pull requests will self-assign them. Sometimes, an author will delegate to someone else. If in doubt, ask the assignee whether it is okay to land.
Never use GitHub's green "Merge Pull Request" button. Reasons for not using the web interface button:
- The "Create a merge commit" method will add an unnecessary merge commit.
- The "Squash and merge" method will add metadata (the pull request #) to the commit title. If more than one author contributes to the pull request, squashing only keeps one author.
- The "Rebase and merge" method has no way of adding metadata to the commit.
Make sure CI is complete and green. If the CI is not green, check for unreliable tests and infrastructure failures. If there are not corresponding issues in the node or build repositories, open new issues. Run a new CI any time someone pushes new code to the pull request.
Check that the commit message adheres to commit message guidelines.
Add all necessary metadata to commit messages before landing. If you are unsure exactly how to format the commit messages, use the commit log as a reference. See this commit as an example.

For pull requests from first-time contributors, be welcoming. Also, verify that their git settings are to their liking.

All commits should be self-contained, meaning every commit should pass all tests. This makes it much easier when bisecting to find a breaking change.

Using `git-node`

In most cases, using the git-node command of node-core-utils should be enough to land a pull request. If you discover a problem when using this tool, please file an issue to the issue tracker.

Quick example:

$ npm install -g node-core-utils
$ git node land $PRID

To use node-core-utils, you will need a GitHub access token. If you do not have one, node-core-utils will create one for you the first time you use it. To do this, it will ask for your GitHub password and two-factor authentication code. If you wish to create the token yourself in advance, see the node-core-utils guide.

Technical HOWTO

Clear any am/rebase that may already be underway:

$ git am --abort
$ git rebase --abort

Checkout proper target branch:

$ git checkout master

Update the tree (assumes your repo is set up as detailed in CONTRIBUTING.md):

$ git fetch upstream
$ git merge --ff-only upstream/master

Apply external patches:

$ curl -L https://github.com/nodejs/node/pull/xxx.patch | git am --whitespace=fix

If the merge fails even though recent CI runs were successful, try a 3-way merge:

$ git am --abort
$ curl -L https://github.com/nodejs/node/pull/xxx.patch | git am -3 --whitespace=fix

If the 3-way merge succeeds, check the results against the original pull request. Build and test on at least one platform before landing.

If the 3-way merge fails, then it is most likely that a conflicting pull request has landed since the CI run. You will have to ask the author to rebase.

Check and re-review the changes:

$ git diff upstream/master

Check the number of commits and commit messages:

$ git log upstream/master...master

Squash commits and add metadata:

$ git rebase -i upstream/master

This will open a screen like this (in the default shell editor):

pick 6928fc1 crypto: add feature A
pick 8120c4c add test for feature A
pick 51759dc crypto: feature B
pick 7d6f433 test for feature B

# Rebase f9456a2..7d6f433 onto f9456a2
#
# Commands:
#  p, pick = use commit
#  r, reword = use commit, but edit the commit message
#  e, edit = use commit, but stop for amending
#  s, squash = use commit, but meld into previous commit
#  f, fixup = like "squash", but discard this commit's log message
#  x, exec = run command (the rest of the line) using shell
#
# These lines can be re-ordered; they are executed from top to bottom.
#
# If you remove a line here THAT COMMIT WILL BE LOST.
#
# However, if you remove everything, the rebase will be aborted.
#
# Note that empty commits are commented out

Replace a couple of picks with fixup to squash them into a previous commit:

pick 6928fc1 crypto: add feature A
fixup 8120c4c add test for feature A
pick 51759dc crypto: feature B
fixup 7d6f433 test for feature B

Replace pick with reword to change the commit message:

reword 6928fc1 crypto: add feature A
fixup 8120c4c add test for feature A
reword 51759dc crypto: feature B
fixup 7d6f433 test for feature B

Save the file and close the editor. When prompted, enter a new commit message for that commit. This is an opportunity to fix commit messages.

The commit message text must conform to the commit message guidelines.

Change the original commit message to include metadata. (The git node metadata command can generate the metadata for you.)
- Required: A PR-URL: line that references the full GitHub URL of the pull request. This makes it easy to trace a commit back to the conversation that led up to that change.
- Optional: A Fixes: X line, where X is the full GitHub URL for an issue. A commit message may include more than one Fixes: lines.
- Optional: One or more Refs: lines referencing a URL for any relevant background.
- Required: A Reviewed-By: Name <email> line for each Collaborator who reviewed the change.
  - Useful for @mentions / contact list if something goes wrong in the PR.
  - Protects against the assumption that GitHub will be around forever.

Other changes may have landed on master since the successful CI run. As a precaution, run tests (make -j4 test or vcbuild test).

Confirm that the commit message format is correct using core-validate-commit.

$ git rev-list upstream/master...HEAD | xargs core-validate-commit

Optional: For your own commits, force push the amended commit to the pull request branch. If your branch name is bugfix, then: git push --force-with-lease origin master:bugfix. Don't close the PR. It will close after you push it upstream. It will have the purple merged status rather than the red closed status. If you close the PR before GitHub adjusts its status, it will show up as a 0 commit PR with no changed files. The order of operations is important. If you push upstream before you push to your branch, GitHub will close the issue with the red closed status.

Time to push it:

$ git push upstream master

Close the pull request with a "Landed in <commit hash>" comment. If your pull request shows the purple merged status then you should still add the "Landed in .." comment if you added more than one commit.

Troubleshooting

Sometimes, when running git push upstream master, you may get an error message like this:

To https://github.com/nodejs/node
 ! [rejected]              master -> master (fetch first)
error: failed to push some refs to 'https://github.com/nodejs/node'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

That means a commit has landed since your last rebase against upstream/master. To fix this, pull with rebase from upstream and run the tests again (to make sure no interactions between your changes and the new changes cause any problems), and push again:

git pull upstream master --rebase
make -j4 test
git push upstream master

I Made a Mistake

Ping a TSC member.
#node-dev on freenode
With git, there's a way to override remote trees by force pushing (git push -f). This should generally be seen as forbidden (since you're rewriting history on a repository other people are working against) but is allowed for simpler slip-ups such as typos in commit messages. However, you are only allowed to force push to any Node.js branch within 10 minutes from your original push. If someone else pushes to the branch or the 10 minute period passes, consider the commit final.
- Use --force-with-lease to minimize the chance of overwriting someone else's change.
- Post to #node-dev (IRC) if you force push.

Long Term Support

What is LTS?

Long Term Support (often referred to as LTS) guarantees application developers a 30-month support cycle with specific versions of Node.js.

You can find more information in the full release plan.

How does LTS work?

Once a Current branch enters LTS, changes in that branch are limited to bug fixes, security updates, possible npm updates, documentation updates, and certain performance improvements that can be demonstrated to not break existing applications. Semver-minor changes are only permitted if required for bug fixes and then only on a case-by-case basis with LTS WG and possibly Technical Steering Committee (TSC) review. Semver-major changes are permitted only if required for security-related fixes.

Once a Current branch moves into Maintenance mode, only critical bugs, critical security fixes, and documentation updates will be permitted.

Landing semver-minor commits in LTS

The default policy is to not land semver-minor or higher commits in any LTS branch. However, the LTS WG or TSC can evaluate any individual semver-minor commit and decide whether a special exception ought to be made. It is expected that such exceptions would be evaluated, in part, on the scope and impact of the changes on the code, the risk to ecosystem stability incurred by accepting the change, and the expected benefit that landing the commit will have for the ecosystem.

Any Collaborator who feels a semver-minor commit should be landed in an LTS branch should attach the lts-agenda label to the pull request. The LTS WG will discuss the issue and, if necessary, will escalate the issue up to the TSC for further discussion.

How are LTS Branches Managed?

There are multiple LTS branches, e.g. v10.x and v8.x. Each of these is paired with a staging branch: v10.x-staging and v8.x-staging.

As commits land on the master branch, they are cherry-picked back to each staging branch as appropriate. If the commit applies only to the LTS branch, the PR must be opened against the staging branch. Commits are selectively pulled from the staging branch into the LTS branch only when a release is being prepared and may be pulled into the LTS branch in a different order than they were landed in staging.

Only the members of the @nodejs/backporters team should land commits onto LTS staging branches.

How can I help?

When you send your pull request, please include information about whether your change is breaking. If you think your patch can be backported, please include that information in the PR thread or your PR description. For more information on backporting, please see the backporting guide.

Several LTS related issue and PR labels have been provided:

lts-watch-v10.x - tells the LTS WG that the issue/PR needs to be considered for landing in the v10.x-staging branch.
lts-watch-v8.x - tells the LTS WG that the issue/PR needs to be considered for landing in the v8.x-staging branch.
lts-watch-v6.x - tells the LTS WG that the issue/PR needs to be considered for landing in the v6.x-staging branch.
land-on-v10.x - tells the release team that the commit should be landed in a future v10.x release.
land-on-v8.x - tells the release team that the commit should be landed in a future v8.x release.
land-on-v6.x - tells the release team that the commit should be landed in a future v6.x release.

Any Collaborator can attach these labels to any PR/issue. As commits are landed into the staging branches, the lts-watch- label will be removed. Likewise, as commits are landed in a LTS release, the land-on- label will be removed.

Collaborators are encouraged to help the LTS WG by attaching the appropriate lts-watch- label to any PR that may impact an LTS release.

How is an LTS release cut?

When the LTS working group determines that a new LTS release is required, selected commits will be picked from the staging branch to be included in the release. This process of making a release will be a collaboration between the LTS working group and the Release team.

Who to CC in the issue tracker

Subsystem	Maintainers
`benchmark/*`	@nodejs/benchmarking, @mscdex
`doc/`, `.md`	@nodejs/documentation
`lib/assert`	@nodejs/assert
`lib/async_hooks`	@nodejs/async_hooks for bugs/reviews (+ @nodejs/diagnostics for API)
`lib/buffer`	@nodejs/buffer
`lib/child_process`	@nodejs/child_process
`lib/cluster`	@nodejs/cluster
`lib/{crypto,tls,https}`	@nodejs/crypto
`lib/dgram`	@nodejs/dgram
`lib/domains`	@nodejs/domains
`lib/fs`, `src/{fs,file}`	@nodejs/fs
`lib/{_}http{*}`	@nodejs/http
`lib/inspector.js`, `src/inspector_*`	@nodejs/v8-inspector
`lib/internal/bootstrap/*`	@nodejs/process
`lib/internal/url`, `src/node_url`	@nodejs/url
`lib/net`	@bnoordhuis, @indutny, @nodejs/streams
`lib/repl`	@nodejs/repl
`lib/{_}stream{*}`	@nodejs/streams
`lib/timers`	@nodejs/timers
`lib/util`	@nodejs/util
`lib/zlib`	@nodejs/zlib
`src/async_wrap.*`	@nodejs/async_hooks
`src/node_api.*`	@nodejs/n-api
`src/node_crypto.*`	@nodejs/crypto
`test/*`	@nodejs/testing
`tools/node_modules/eslint`, `.eslintrc`	@nodejs/linting
build	@nodejs/build
`src/module_wrap.`, `lib/internal/modules/`, `lib/internal/vm/module.js`	@nodejs/modules
GYP	@nodejs/gyp
performance	@nodejs/performance
platform specific	@nodejs/platform-{aix,arm,freebsd,macos,ppc,smartos,s390,windows}
python code	@nodejs/python
upgrading c-ares	@rvagg
upgrading http-parser	@nodejs/http, @nodejs/http2
upgrading libuv	@nodejs/libuv
upgrading npm	@fishrock123, @MylesBorins
upgrading V8	@nodejs/V8, @nodejs/post-mortem
Embedded use or delivery of Node.js	@nodejs/delivery-channels

When things need extra attention, are controversial, or semver-major: @nodejs/tsc

If you cannot find who to cc for a file, git shortlog -n -s <file> may help.

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