# Contributing Guidelines

There are two main ways to contribute to the project &mdash; submitting issues and submitting 
fixes/changes/improvements via pull requests.

## Submitting issues

Both bug reports and feature requests are welcome.
Submit issues [here](https://github.com/Kotlin/kotlinx.coroutines/issues).
Questions about usage and general inquiries are better suited for [StackOverflow](https://stackoverflow.com)
or the `#coroutines` channel in [KotlinLang Slack](https://surveys.jetbrains.com/s3/kotlin-slack-sign-up).

## Submitting PRs

We love PRs. Submit PRs [here](https://github.com/Kotlin/kotlinx.coroutines/pulls).
However, please keep in mind that maintainers will have to support the resulting code of the project,
so do familiarize yourself with the following guidelines. 

* All development (both new features and bug fixes) is performed in the `develop` branch.
  * The `master` branch contains the sources of the most recently released version.
  * Base your PRs against the `develop` branch.
  * The `develop` branch is pushed to the `master` branch during release.
  * Documentation in markdown files can be updated directly in the `master` branch, 
    unless the documentation is in the source code, and the patch changes line numbers.
* If you fix documentation:
  * After fixing/changing code examples in the [`docs`](docs) folder or updating any references in the markdown files
    run the [Knit tool](#running-the-knit-tool) and commit the resulting changes as well. 
    The tests will not pass otherwise.
  * If you plan extensive rewrites/additions to the docs, then please [contact the maintainers](#contacting-maintainers)
    to coordinate the work in advance.
* If you make any code changes:
  * Follow the [Kotlin Coding Conventions](https://kotlinlang.org/docs/reference/coding-conventions.html). 
    Use 4 spaces for indentation.
    Do not add extra newlines in function bodies: if you feel that blocks of code should be logically separated,
    then separate them with a comment instead.
  * [Build the project](#building) to make sure everything works and passes the tests.
* If you fix a bug:
  * Write the test that reproduces the bug.
  * Fixes without tests are accepted only in exceptional circumstances if it can be shown that writing the 
    corresponding test is too hard or otherwise impractical.
  * Follow the style of writing tests that is used in this project: 
    name test functions as `testXxx`. Don't use backticks in test names.
* If you introduce any new public APIs:
  * Comment on the existing issue if you want to work on it or create one beforehand. 
    Ensure that not only the issue describes a problem, but also that the proposed solution has received positive
    feedback. Propose a solution if there isn't any.
    PRs that add new API without a corresponding issue with positive feedback about the proposed implementation are
    unlikely to be approved or reviewed.
  * All new APIs must come with documentation and tests.
  * All new APIs are initially released with the `@ExperimentalCoroutineApi` annotation and graduate later.
  * [Update the public API dumps](#updating-the-public-api-dump) and commit the resulting changes as well. 
    It will not pass the tests otherwise.
  * If you plan large API additions, then please start by submitting an issue with the proposed API design
    to gather community feedback.
  * [Contact the maintainers](#contacting-maintainers) to coordinate any extensive work in advance.

## Building

This library is built with Gradle. 

* Run `./gradlew build` to build. It also runs all the tests.
* Run `./gradlew <module>:check` to test the module you are looking at to speed 
  things up during development.
* Run `./gradlew <module>:jvmTest` to perform only the fast JVM tests of a multiplatform module.
   
You can import this project into IDEA, but you have to delegate build actions
to Gradle (in Preferences -> Build, Execution, Deployment -> Build Tools -> Gradle -> Build and run).

### Environment requirements

* JDK >= 11 referred to by the `JAVA_HOME` environment variable.
* JDK 1.8 referred to by the `JDK_18` environment variable. Only used by nightly stress-tests. 
  It is OK to have `JDK_18` point to a non-1.8 JDK (e.g. `JAVA_HOME`) for external contributions.

For external contributions you can, for example, add this to your shell startup scripts (e.g. `~/.zshrc`):
```shell
# This assumes JAVA_HOME is set already to a JDK >= 11 version
export JDK_18="$JAVA_HOME"
```

### Running the Knit tool

* Use [Knit](https://github.com/Kotlin/kotlinx-knit/blob/main/README.md) for updates to documentation:
  * Run `./gradlew knit` to update the example files, links, tables of content.
  * Commit the updated documents and examples together with other changes.

### Updating the public API dump

* Use the [Binary Compatibility Validator](https://github.com/Kotlin/binary-compatibility-validator/blob/master/README.md) for updates to public API:
  * Run `./gradlew apiDump` to update API index files. 
  * Commit the updated API indexes together with other changes.

## Releases

* The full release procedure checklist is [here](RELEASE.md).

## Contacting maintainers

* If something cannot be done, not convenient, or does not work &mdash; submit an [issue](#submitting-issues).
* "How to do something" questions &mdash; [StackOverflow](https://stackoverflow.com).
* Discussions and general inquiries &mdash; use `#coroutines` channel in [KotlinLang Slack](https://kotl.in/slack).