Contributor Guidelines

Implementation-wise, the following things should be avoided as much as possible:

public mutable state
global state
implicit conversions
threadLocal
locks
casting
introducing new, heavy external dependencies

API design

Play is a Java and Scala framework, make sure your changes are working for both API-s
Java APIs should go to framework/play/src/main/java, package structure is play.myapipackage.xxxx
Scala APIs should go to framework/play/src/main/scala, where the package structure is play.api.myapipackage
Java and Scala APIs should be implemented the following way:
- implement the core API in scala (play.api.xxx)
- if your component requires life cycle management or needs to be swappable, create a plugin, otherwise skip this step
- wrap core API for scala users ([example] (https://github.com/playframework/Play20/blob/master/framework/src/play/src/main/scala/play/api/cache/Cache.scala#L69))
- wrap scala API for java users (example)
features are forever, always think about whether a new feature really belongs to the core framework or it should be implemented as a plugin
if you are in doubt, ask on the mailing list

Testing and documentation

each and every public facing method and class need to have a corresponding scaladoc or javadoc with examples, description etc.
each feature and bug fix requires either a functional test (framework/integrationtest) or a spec (/play/src/test)
run Play's integration test suite framework/runtests before pushing. If a test fails, fix it, do not ignore it.

source format

run scalariform-format before commit

git commits

prefer rebase
bigger changesets

lighthouse

Please always create a corresponding ticket in Lighthouse before sending a pull request