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Contributing to RxJS

Read and abide by the Code of Conduct! Even if you don't read it, it still applies to you. Ignorance is not an exemption.

Contents

(This document is a work in progress and is subject to change)

Submitting a Pull Request (PR)

Before you submit your Pull Request (PR) consider the following guidelines:

  • Search GitHub for an open or closed PR that relates to your submission. You don't want to duplicate effort.

  • Make your changes in a new git branch:

    git checkout -b my-fix-branch master

  • Create your patch, following code style guidelines, and including appropriate test cases.

  • Run the full test suite and ensure that all tests pass.

  • Commit your changes using a descriptive commit message that follows our commit message guidelines. Adherence to these conventions is necessary because release notes are automatically generated from these messages.

    git commit -a

    Note: the optional commit -a command line option will automatically "add" and "rm" edited files.

  • Push your branch to GitHub:

    git push origin my-fix-branch

  • In GitHub, send a pull request to RxJS:master.

  • If we suggest changes then:

    • Make the required updates.

    • Re-run the test suites to ensure tests are still passing.

    • Re-run performance tests to make sure your changes didn't hurt performance.

    • Rebase your branch and force push to your GitHub repository (this will update your Pull Request):

      git rebase master -i
git push -f

    • When updating your feature branch with the requested changes, please do not overwrite the commit history, but rather contain the changes in new commits. This is for the sake of a clearer and easier review process.

That's it! Thank you for your contribution!

After your pull request is merged

After your pull request is merged, you can safely delete your branch and pull the changes from the main (upstream) repository:

  • Delete the remote branch on GitHub either through the GitHub web UI or your local shell as follows:

    git push origin --delete my-fix-branch

  • Check out the master branch:

    git checkout master -f

  • Delete the local branch:

    git branch -D my-fix-branch

  • Update your master with the latest upstream version:

    git pull --ff upstream master

Coding Style Guidelines

  • Please use proper types and generics throughout your code.
  • 2 space indentation only
  • favor readability over terseness

(TBD): For now, try to follow the style that exists elsewhere in the source, and use your best judgment.

Documentation

  • The documentation is auto-generated directly from the source code.
  • In short: From the source code we generate JSON documents, describing each operator, function ... and render this JSON within an Angular application
  • The folder apps/rxjs.dev contains everything you need for building and developing the docs
  • The Documentation README will support you
  • After a PR is merged to master the docs will be published to https://rxjs.dev/

Unit Tests

Unit tests are located under the spec directory. Unit tests over synchronous operators and operations can be written in a standard chai style. Unit tests written against any asynchronous operator should be written in Marble Test Style outlined in detail here.

Each operator under test must be in its own file to cover the following cases:

  • Never
  • Empty
  • Single/Multiple Values
  • Error in the sequence
  • Never ending sequences
  • Early disposal in sequences

If the operator accepts a function as an argument from the user/developer (for example filter(fn) or zip(a, fn)), then it must cover the following cases:

  • Success with all values in the callback
  • Success with the context, if any allowed in the operator signature
  • If an error is thrown

CI Tests

  • Using Travis on your forked version of RxJS will allow running CI tests on that fork before submitting a PR to master
  • Simply create a Travis account and add your fork as a new project
  • Sauce Labs setup will allow performing automated browser tests on the fork. Since saucelabs doesn't perform browser tests on a PR, this will help verify test results before PR's are checked into master.
  • In your Travis repo configuration, set the environment variables SAUCE_USERNAME and SAUCE_ACCESS_KEY to your saucelabs account (reference)
  • As master runs both of these tests per each check in, it'd be welcome to setup those test before creating your PR

Performance Tests

One of the primary goals of this library is (and will continue to be) great performance. As such, we've employed a variety of performance testing techniques.

  • DON'T labor over minute variations in ops/sec or milliseconds, there will always be variance in perf test results.
  • DON'T alter a performance test unless absolutely necessary. Performance tests may be compared to previous results from previous builds.
  • DO run tests multiple times and make sure the margins of error are low
  • DO run tests in your feature branches and compare them to master
  • DO add performance tests for all new operators
  • DO add performance tests that you feel are missing from other operators
  • DO add additional performance tests for all worthy code paths. If you develop an operator with special handling for scalar observables, please add tests for those scenarios

Macro

Macro performance tests are best written for scenarios where many object instance allocations (or deallocations) are occurring. Operators that create a lot of child subscriptions or operators that emit new objects like Observables and Subjects are definitely worth creating macro performance tests for.

Other scenarios for macro performance testing may include common end-to-end scenarios from real-world apps. If you have a situation in your app where you feel RxJS is performing poorly, please submit an issue and include a minimal code example showing your performance issues. We would love to solve perf for your real-world problems and add those tests to our perf test battery.

Macro performance tests can be run by hosting the root directory with any web server (we use http-server), then running:

yarn build_all
protractor protractor.conf.js

Micro

Micro performance tests really only serve to test operations per second. They're quick and easy to develop, and provide a reasonable look into the relative performance of our operators versus prior versions. All operators should have corresponding micro performance tests.

Micro performance test can be run with:

yarn build_all
node perf/micro

If you wish to run a single micro performance test, you can do so by providing a single argument with the name of the perf test file(s):

node perf/micro zip

Commit Message Guidelines

We have very precise rules over how our git commit messages can be formatted. This leads to more readable messages that are easy to follow when looking through the project history. But also, we use the git commit messages to generate the RxJS change log. Helper script yarn commit provides command line based wizard to format commit message easily.

Commit Message Format

Each commit message consists of a header, a body and a footer. The header has a special format that includes a type, a scope and a subject:

<type>(<scope>): <subject>
<BLANK LINE>
<body>
<BLANK LINE>
<footer>

The header is mandatory and the scope of the header is optional.

Any line of the commit message cannot be longer than 100 characters! This allows the message to be easier to read on GitHub as well as in various git tools.

Revert

If the commit reverts a previous commit, it should begin with revert:, followed by the header of the reverted commit. In the body it should say: This reverts commit <hash>., where the hash is the SHA of the commit being reverted.

Type

Must be one of the following:

  • feat: A new feature
  • fix: A bug fix
  • docs: Documentation only changes
  • style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
  • refactor: A code change that neither fixes a bug nor adds a feature
  • perf: A code change that improves performance
  • test: Adding missing tests
  • chore: Changes to the build process or auxiliary tools and libraries such as documentation generation

Scope

The scope could be anything specifying the place of the commit change. For example Observable, Subject, switchMap, etc.

Subject

The subject contains succinct description of the change:

  • use the imperative, present tense: "change" not "changed" nor "changes"
  • don't capitalize first letter
  • no dot (.) at the end

Body

Just as in the subject, use the imperative, present tense: "change" not "changed" nor "changes". The body should include the motivation for the change and contrast this with previous behavior.

Footer

The footer should contain any information about Breaking Changes and is also the place to reference GitHub issues that this commit Closes.

Breaking Changes should start with the word BREAKING CHANGE: with a space or two newlines. The rest of the commit message is then used for this.