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swift-nio/CONTRIBUTING.md

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Legal

By submitting a pull request, you represent that you have the right to license your contribution to Apple and the community, and agree by submitting the patch that your contributions are licensed under the Apache 2.0 license (see LICENSE.txt).

How to submit a bug report

Please ensure to specify the following:

  • SwiftNIO commit hash
  • Contextual information (e.g. what you were trying to achieve with SwiftNIO)
  • Simplest possible steps to reproduce
    • More complex the steps are, lower the priority will be.
    • A pull request with failing test case is preferred, but it's just fine to paste the test case into the issue description.
  • Anything that might be relevant in your opinion, such as:
    • Swift version or the output of swift --version
    • OS version and the output of uname -a
    • Network configuration

Example

SwiftNIO commit hash: 22ec043dc9d24bb011b47ece4f9ee97ee5be2757

Context:
While load testing my HTTP web server written with SwiftNIO, I noticed
that one file descriptor is leaked per request.

Steps to reproduce:
1. ...
2. ...
3. ...
4. ...

$ swift --version
Swift version 4.0.2 (swift-4.0.2-RELEASE)
Target: x86_64-unknown-linux-gnu

Operating system: Ubuntu Linux 16.04 64-bit

$ uname -a
Linux beefy.machine 4.4.0-101-generic #124-Ubuntu SMP Fri Nov 10 18:29:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

My system has IPv6 disabled.

Writing a Patch

A good SwiftNIO patch is:

  1. Concise, and contains as few changes as needed to achieve the end result.
  2. Tested, ensuring that any tests provided failed before the patch and pass after it.
  3. Documented, adding API documentation as needed to cover new functions and properties.
  4. Accompanied by a great commit message, using our commit message template.

Commit Message Template

We require that your commit messages match our template. The easiest way to do that is to get git to help you by explicitly using the template. To do that, cd to the root of our repository and run:

git config commit.template dev/git.commit.template

The default policy for taking contributions is “Squash and Merge” - because of this the commit message format rule above applies to the PR rather than every commit contained within it.

Make sure Tests work on Linux

SwiftNIO uses XCTest to run tests on both macOS and Linux. While the macOS version of XCTest is able to use the Objective-C runtime to discover tests at execution time, the Linux version is not (prior to swift 5.1). For this reason, whenever you add new tests you have to run a script that generates the hooks needed to run those tests on Linux, or our CI will complain that the tests are not all present on Linux. To do this, merely execute ruby ./scripts/generate_linux_tests.rb at the root of the package and check the changes it made.

Make sure your patch works for all supported versions of swift

The CI will do this for you. You can use the docker-compose files included if you wish to check locally. Currently all versions of swift >= 5.6 are supported. For example usage of docker compose see the main README

Make sure your code is performant

SwiftNIO has been created to be high performance. The integration tests cover some measures of performance including allocations which should be avoided if possible. For help with allocation problems refer to the guide to allocation debugging

Formatting

Try to keep your lines less than 120 characters long so github can correctly display your changes.

It is intended SwiftNIO will use the swift-format tool in the future to bring consistency to code formatting. To follow the discussion on this topic see the swift evolution proposal SE-250

Extensibility

Try to make sure your code is robust to future extensions. The public interface is very hard to change after release - please refer to the API guidelines

How to contribute your work

Please open a pull request at https://github.com/apple/swift-nio. Make sure the CI passes, and then wait for code review.

After review you may be asked to make changes. When you are ready, use the request re-review feature of github or mention the reviewers by name in a comment.