# Hacking on Draft

This guide is for developers who want to improve Draft. These instructions will help you set up a
development environment for working on the Draft source code.

## Prerequisites

To compile and test Draft binaries and to build Docker images, you will need:

 - a [Kubernetes][] cluster. We recommend [minikube][].
 - [docker][]
 - [git][]
 - [helm][], using the same version as recommended in the [installation guide][install].
 - [Go][] 1.8 or later, with support for compiling to `linux/amd64`

In most cases, install the prerequisite according to its instructions. See the next section
for a note about Go cross-compiling support.

### Configuring Go

Draft's binary executables are built on your machine and then copied into a Docker image. This
requires your Go compiler to support the `linux/amd64` target architecture. If you develop on a
machine that isn't AMD64 Linux, make sure that `go` has support for cross-compiling.

On macOS, a cross-compiling Go can be installed with [Homebrew][]:

```shell
$ brew install go --with-cc-common
```

It is also straightforward to build Go from source:

```shell
$ sudo su
$ curl -sSL https://storage.googleapis.com/golang/go1.10.src.tar.gz | tar -C /usr/local -xz
$ cd /usr/local/go/src
$ # compile Go for the default platform first, then add cross-compile support
$ ./make.bash --no-clean
$ GOOS=linux GOARCH=amd64 ./make.bash --no-clean
```

## Fork the Repository

Begin at Github by forking Draft, then clone your fork locally. Since Draft is a Go package, it
should be located at `$GOPATH/src/github.com/Azure/draft`.

```shell
$ mkdir -p $GOPATH/src/github.com/Azure
$ cd $GOPATH/src/github.com/Azure
$ git clone git@github.com:<username>/draft.git
$ cd draft
```

Add the conventional [upstream][] `git` remote in order to fetch changes from Draft's main master
branch and to create pull requests:

```shell
$ git remote add upstream https://github.com/Azure/draft.git
```

## Build Your Changes

With the prerequisites installed and your fork of Draft cloned, you can make changes to local Draft
source code.

Run `make` to build `draft`:

```shell
$ make bootstrap
$ make
```

## Test Your Changes

Draft includes a suite of tests.
- `make test-lint`: runs linter/style checks
- `make test-unit`: runs basic unit tests
- `make test`: runs all of the above

## Cleaning Up

```shell
$ make clean
```


[docker]: https://www.docker.com/
[install]: ../install.md
[git]: https://git-scm.com/
[go]: https://golang.org/
[helm]: https://github.com/kubernetes/helm
[Homebrew]: https://brew.sh/
[Kubernetes]: https://github.com/kubernetes/kubernetes
[minikube]: https://github.com/kubernetes/minikube
[upstream]: https://help.github.com/articles/fork-a-repo/