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Node.js Collaborator Guide

Contents

This document explains how Collaborators manage the Node.js project. Collaborators should understand the guidelines for new contributors and the project governance model.

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 First-time contributor 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

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. Collaborators should take significant care when making and reviewing such changes. An effort must be made 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.

When Breaking Changes Actually Break Things

Because breaking (semver-major) changes are permitted to land on the master branch at any time, at least some subset of the user ecosystem may be adversely affected in the short term when attempting to build and use Node.js directly from the master branch. This potential instability is why Node.js offers distinct Current and LTS release streams that offer explicit stability guarantees.

Specifically:

  • Breaking changes should never land in Current or LTS except when:
    • Resolving critical security issues.
    • Fixing a critical bug (e.g. fixing a memory leak) requires a breaking change.
    • There is TSC consensus that the change is required.
  • If a breaking commit does accidentally land in a Current or LTS branch, an attempt to fix the issue will be made before the next release; If no fix is provided then the commit will be reverted.

When any changes are landed on the master branch and it is determined that the changes do break existing code, a decision may be made to revert those changes either temporarily or permanently. However, the decision to revert or not can often be based on many complex factors that are not easily codified. It is also possible that the breaking commit can be labeled retroactively as a semver-major change that will not be backported to Current or LTS branches.

Reverting commits

Commits are reverted with git revert <HASH>, or git revert <FROM>..<TO> for multiple commits. Commit metadata and the reason for the revert should be appended. Commit message rules about line length and subsystem can be ignored. A Pull Request should be raised and approved like any other change.

Introducing New Modules

Semver-minor commits that introduce new core modules should be treated with extra care.

The name of the new core module should not conflict with any existing module in the ecosystem unless a written agreement with the owner of those modules is reached to transfer ownership.

If the new module name is free, a Collaborator should register a placeholder in the module registry as soon as possible, linking to the pull request that introduces the new core module.

Pull requests introducing new core modules:

  • Must be left open for at least one week for review.
  • Must be labeled using the tsc-review label.
  • Must have signoff from at least two TSC members.

New core modules must be landed with a Stability Index of Experimental, and must remain Experimental until a semver-major release.

Additions to N-API

N-API provides an ABI stable API that we will have to support in future versions without the usual option to modify or remove existing APIs on SemVer boundaries. Therefore, additions need to be managed carefully.

This guide outlines the requirements and principles that we should follow when approving and landing new N-API APIs (any additions to node_api.h and node_api_types.h).

Deprecations

Deprecation is "the discouragement of use of some … feature … or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing it or prohibiting its use. It can also imply that a feature, design, or practice will be removed or discontinued entirely in the future."

Node.js uses three Deprecation levels:

  • Documentation-Only Deprecation: A deprecation notice is added to the API documentation but no functional changes are implemented in the code. By default, there will be no warnings emitted for such deprecations at runtime. Documentation-only deprecations may trigger a runtime warning when Node.js is started with the --pending-deprecation flag or the NODE_PENDING_DEPRECATION=1 environment variable is set.

  • Runtime Deprecation: A warning is emitted at runtime the first time that a deprecated API is used. The --throw-deprecation flag can be used to escalate such warnings into runtime errors that will cause the Node.js process to exit. As with Documentation-Only Deprecation, the documentation for the API must be updated to clearly indicate the deprecated status.

  • 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.

Documentation-Only Deprecations may be handled as semver-minor or semver-major changes. Such deprecations have no impact on the successful operation of running code and therefore should not be viewed as breaking changes.

Runtime Deprecations and End-of-life APIs (internal or public) must be handled as semver-major changes unless there is TSC consensus to land the deprecation as a semver-minor.

All Documentation-Only and Runtime deprecations will be assigned a unique identifier that can be used to persistently refer to the deprecation in documentation, emitted process warnings, or errors thrown. Documentation for these identifiers will be included in the Node.js API documentation and will be immutable once assigned. Even if End-of-Life code is removed from Node.js, the documentation for the assigned deprecation identifier must remain in the Node.js API documentation.

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 but must not be upgraded to a Runtime Deprecation until the next major release.

No API can be moved to End-of-life without first having gone through a Runtime Deprecation cycle. However, there is no requirement that deprecated code must progress ultimately to End-of-Life. Documentation-only and runtime deprecations may remain indefinitely.

Communicate pending deprecations and associated mitigations with the ecosystem as soon as possible (preferably before the pull request adding the deprecation lands on the master branch). Use the notable-change label on all pull requests that add a new deprecation or move an existing deprecation to a new deprecation level.

Involving the TSC

Collaborators may opt to elevate pull requests or issues to the TSC. This should be done where a pull request:

  • is labeled semver-major, or
  • has a significant impact on the codebase, or
  • is inherently controversial, or
  • has failed to reach consensus amongst the Collaborators who are actively participating in the discussion.

Assign the tsc-review label or @-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

  1. Avoid landing PRs that are assigned to someone else. Authors who wish to land their own PRs will self-assign them, or delegate to someone else. If in doubt, ask the assignee whether it is okay to land.
  2. 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 PR #) to the commit title. If more than one author has contributed to the PR, squashing will only keep the most recent author.
    • The "Rebase and merge" method has no way of adding metadata to the commit.
  3. Make sure the CI is done and the result is green. If the CI is not green, check for flaky tests and infrastructure failures. Please check if those were already reported in the appropriate repository (node and build) or not and open new issues in case they are not. If no CI was run or the run is outdated because code was pushed after the last run, please first start a new CI and wait for the result. If no CI is required, please leave a comment in case none is already present.
  4. Review the commit message to ensure that it adheres to the guidelines outlined in the contributing guide.
  5. 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 PRs 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 help you 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

If it's the first time you have used node-core-utils, you will be prompted to type the password of your GitHub account and the two-factor authentication code in the console so the tool can create the GitHub access token for you. If you do not want to do that, follow the node-core-utils guide to set up your credentials manually.

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, then a 3-way merge may be required. In this case try:

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

If the 3-way merge succeeds you can proceed, but make sure to check the changes against the original PR carefully and build/test on at least one platform before landing. If the 3-way merge fails, then it is most likely that a conflicting PR has landed since the CI run and 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. You'll be asked to enter a new commit message for that commit. This is a good moment to fix incorrect commit logs, ensure that they are properly formatted, and add Reviewed-By lines.

  • Modify the original commit message to include additional metadata regarding the change process. (The git node metadata command can generate the metadata for you.)

    • Required: A PR-URL: line that references the full GitHub URL of the original pull request being merged so it's easy to trace a commit back to the conversation that led up to that change.
    • Optional: A Fixes: X line, where X either includes the full GitHub URL for an issue, and/or the hash and commit message if the commit fixes a bug in a previous commit. Multiple Fixes: lines may be added if appropriate.
    • Optional: One or more Refs: lines referencing a URL for any relevant background.
    • Required: A Reviewed-By: Name <email> line for yourself and any other Collaborators who have 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.

Run tests (make -j4 test or vcbuild test). Even though there was a successful continuous integration run, other changes may have landed on master since then, so running the tests one last time locally is a good practice.

Validate that the commit message is properly formatted using core-validate-commit.

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

Optional: When landing your own commits, force push the amended commit to the branch you used to open the pull request. If your branch is called bugfix, then the command would be git push --force-with-lease origin master:bugfix. Don't manually close the PR, GitHub will close it automatically later after you push it upstream, and will mark it with 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 and the changed file history will be empty. Also if you push upstream before you push to your branch, GitHub will close the issue with red status so the order of operations is important.

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 multiple commits.

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.