# Contributing to Packer

**First:** if you're unsure or afraid of _anything_, just ask
or submit the issue or pull request anyways. You won't be yelled at for
giving your best effort. The worst that can happen is that you'll be
politely asked to change something. We appreciate any sort of contributions,
and don't want a wall of rules to get in the way of that.

However, for those individuals who want a bit more guidance on the
best way to contribute to the project, read on. This document will cover
what we're looking for. By addressing all the points we're looking for,
it raises the chances we can quickly merge or address your contributions.

## Issues

### Reporting an Issue

* Make sure you test against the latest released version. It is possible
  we already fixed the bug you're experiencing.

* Run the command with debug ouput with the environment variable
  `PACKER_LOG`. For example: `PACKER_LOG=1 packer build template.json`. Take
  the *entire* output and create a [gist](https://gist.github.com) for linking
  to in your issue. Packer should strip sensitive keys from the output,
  but take a look through just in case.

* Provide a reproducible test case. If a contributor can't reproduce an
  issue, then it dramatically lowers the chances it'll get fixed. And in
  some cases, the issue will eventually be closed.

* Respond promptly to any questions made by the Packer team to your issue.
  Stale issues will be closed.

### Issue Lifecycle

1. The issue is reported.

2. The issue is verified and categorized by a Packer collaborator.
   Categorization is done via tags. For example, bugs are marked as "bugs"
   and easy fixes are marked as "easy".

3. Unless it is critical, the issue is left for a period of time (sometimes
   many weeks), giving outside contributors a chance to address the issue.

4. The issue is addressed in a pull request or commit. The issue will be
   referenced in the commit message so that the code that fixes it is clearly
   linked.

5. The issue is closed.

## Setting up Go to work on Packer

If you have never worked with Go before, you will have to complete the
following steps in order to be able to compile and test Packer. These instructions target POSIX-like environments (Mac OS X, Linux, Cygwin, etc.) so you may need to adjust them for Windows or other shells.

1. [Download](https://golang.org/dl) and install Go. The instructions below
   are for go 1.6. Earlier versions of Go are no longer supported.

2. Set and export the `GOPATH` environment variable and update your `PATH`. For
   example, you can add to your `.bash_profile`.

    ```
    export GOPATH=$HOME/go
    export PATH=$PATH:$GOPATH/bin
    ```

3. Download the Packer source (and its dependencies) by running `go get
   github.com/mitchellh/packer`. This will download the Packer source to
   `$GOPATH/src/github.com/mitchellh/packer`.

4. When working on packer `cd $GOPATH/src/github.com/mitchellh/packer` so you
   can run `make` and easily access other files. Run `make help` to get
   information about make targets.

5. Make your changes to the Packer source. You can run `make` in
   `$GOPATH/src/github.com/mitchellh/packer` to run tests and build the packer
   binary. Any compilation errors will be shown when the binaries are
   rebuilding. If you don't have `make` you can simply run `go build -o bin/packer .` from the project root.

6. After running building packer successfully, use
   `$GOPATH/src/github.com/mitchellh/packer/bin/packer` to build a machine and
   verify your changes work. For instance: `$GOPATH/src/github.com/mitchellh/packer/bin/packer build template.json`.

7. If everything works well and the tests pass, run `go fmt` on your code
   before submitting a pull-request.

### Opening an Pull Request

When you are ready to open a pull-request, you will need to [fork packer](https://github.com/mitchellh/packer#fork-destination-box), push your changes to your fork, and then open a pull-request.

For example, my github username is `cbednarski` so I would do the following:

    git checkout -b f-my-feature
    // develop a patch
    git push https://github.com/cbednarski/packer f-my-feature

From there, open your fork in your browser to open a new pull-request.

**Note** Go infers package names from their filepaths. This means `go build` will break if you `git clone` your fork instead of using `go get` on the main packer project.

### Tips for Working on Packer

#### Working on forks

The easiest way to work on a fork is to set it as a remote of the packer project. After following the steps in "Setting up Go to work on Packer":

1. Navigate to $GOPATH/src/github.com/mitchellh/packer
2. Add the remote `git remote add <name of remote> <github url of fork>`. For example `git remote add mwhooker https://github.com/mwhooker/packer.git`.
3. Checkout a feature branch: `git checkout -b new-feature`
4. Make changes
5. (Optional) Push your changes to the fork: `git push -u <name of remote> new-feature`

This way you can push to your fork to create a PR, but the code on disk still lives in the spot where the go cli tools are expecting to find it.

#### Govendor

If you are submitting a change that requires new or updated dependencies, please include them in `vendor/vendor.json` and in the `vendor/` folder.  This helps everything get tested properly in CI.

Note that you will need to use [govendor](https://github.com/kardianos/govendor) to do this. This step is recommended but not required; if you don't use govendor please indicate in your PR which dependencies have changed and to what versions.

Use `govendor fetch <project>` to add dependencies to the project. See
[govendor quick
start](https://github.com/kardianos/govendor#quick-start-also-see-the-faq) for
examples.

Please only apply the minimal vendor changes to get your PR to work. Packer does not attempt to track the latest version for each dependency.

#### Running Unit Tests

You can run tests for individual packages using commands like this:

    $ make test TEST=./builder/amazon/...

#### Running Acceptance Tests

Packer has [acceptance tests](https://en.wikipedia.org/wiki/Acceptance_testing)
for various builders. These typically require an API key (AWS, GCE), or
additional software to be installed on your computer (VirtualBox, VMware).

If you're working on a new builder or builder feature and want verify it is functioning (and also hasn't broken anything else), we recommend running the
acceptance tests.

**Warning:** The acceptance tests create/destroy/modify *real resources*, which
may incur costs for real money. In the presence of a bug, it is possible that resources may be left behind, which can cost money even though you were not using them. We recommend running tests in an account used only for that purpose so it is easy to see if there are any dangling resources, and so production resources are not accidentally destroyed or overwritten during testing.

To run the acceptance tests, invoke `make testacc`:

    $ make testacc TEST=./builder/amazon/ebs
    ...

The `TEST` variable lets you narrow the scope of the acceptance tests to a
specific package / folder. The `TESTARGS` variable is recommended to filter
down to a specific resource to test, since testing all of them at once can
sometimes take a very long time.

Acceptance tests typically require other environment variables to be set for
things such as API tokens and keys. Each test should error and tell you which
credentials are missing, so those are not documented here.
