# Contributing to OpenLayers

Thanks for your interest in contributing to OpenLayers development.  Our
preferred means of receiving contributions is through [pull
requests](https://help.github.com/articles/using-pull-requests).

Before accepting a contribution, we ask that you provide us a Contributor
License Agreement.  If you are making your contribution as part of work for
your employer, please follow the guidelines on submitting a [Corporate
Contributor License Agreement](http://www.openlayers.org/ccla.txt).  If you are
making your contribution as an individual, you can submit a digital
[Individual Contributor License Agreement](https://docs.google.com/spreadsheet/viewform?formkey=dGNNVUJEMXF2dERTU0FXM3JjNVBQblE6MQ).

## Coding guidelines

### Formatting

We use the [Closure
Linter](https://developers.google.com/closure/utilities/docs/linter_howto) to
check source files for potential syntax and coding style issues. To execute the
linter run the following after making your changes:

    $ ./build.py lint

This command assumes that the `gjslint` command in on your PATH.

### Compilation

The OpenLayers 3 is compiled and type-checked using the [Closure
Compiler](https://developers.google.com/closure/compiler/). To
compile the code use:

    $ ./build.py build-all

### Documentation

We use [jsdoc3](https://github.com/jsdoc3/jsdoc) to generate the API
documentation.  To ensure that your changes are properly documented (and don't
break API doc generation), run the following:

    $ ./build.py doc

This command assumes that the `jsdoc` command is on your PATH.

### Testing

Any modifications must not break existing tests. We use
[PhantomJS](http://phantomjs.org/) to run tests *headlessly*.
Use the following to run the tests:

    $ ./build.py test

This command assumes that the `phantomjs` command is on your PATH.

### The `precommit` target

The Makefile includes a `precommit` target for running all of the
above (`lint`, `build-all`, `doc`, and `test`). As the name of the
target suggests `./build.py precommit` is the command to run before
committing:

    $ ./build.py precommit

### Commit messages

We follow http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
for the formatting of commit messages.

Basically, here's what a Git commit message should look like:

    Header line: explaining the commit in one line

    Body of commit message is a few lines of text, explaining things
    in more detail, possibly giving some background about the issue
    being fixed, etc etc.

    The body of the commit message can be several paragraphs, and
    please do proper word-wrap and keep columns shorter than about
    74 characters or so. That way "git log" will show things
    nicely even when it's indented.

    Further paragraphs come after blank lines.