Contributing to Terraform

Terraform and its diverse collection of plugins are a collaborative work between HashiCorp employees, independent cloud vendors, and a large open source community. HashiCorp and the Terraform team truly value every issue, pull request, and feature request received on any of its many GitHub repositories. The only prerequisite to contributing to Terraform is an interest to improve the project!

While you do not need to be an expert in any of the following, these are things that are helpful to have or know if you're wanting to contribute more:

Basic knowledge of Terraform. If you're new to Terraform, please see our introduction documentation.
Basic programming knowledge. Terraform and Terraform Plugins are written in the Go programming language, but even if you've never written a line of Go before, you're still welcome to take a dive into the code and submit patches. The community is happy to assist with code reviews and offer guidance specific to Go.
Infrastructure as Code. If this is a new term for you, check out Infrastructure as Code on Wikipedia for a brief introduction. Our Getting Started guide is a great way to get started as well.

HashiCorp vs. Community Providers

We separate providers out into what we call "HashiCorp Providers" and "Community Providers".

HashiCorp providers are providers that we'll dedicate full time resources to improving, supporting the latest features, and fixing bugs. These are providers we understand deeply and are confident we have the resources to manage ourselves.

Community providers are providers where we depend on the community to contribute fixes and enhancements to improve. HashiCorp will run automated tests and ensure these providers continue to work, but will not dedicate full time resources to add new features to these providers. These providers are available in official Terraform releases, but the functionality is primarily contributed.

The current list of HashiCorp Providers is as follows:

Our testing standards are the same for both HashiCorp and Community providers, and HashiCorp runs full acceptance test suites for every provider nightly to ensure Terraform remains stable.

We make the distinction between these two types of providers to help highlight the vast amounts of community effort that goes in to making Terraform great, and to help contributors better understand the role HashiCorp employees play in the various areas of the code base.

Issues

Issue Reporting Checklists

We welcome issues of all kinds including feature requests, bug reports, and general questions. The code and issue tracker for Terraform is at https://github.com/hashicorp/terraform. Each officially supported Terraform Provider has its own GitHub repository in the Terraform Providers GitHub Organization.

Below you'll find checklists with guidelines for well-formed issues of each type.

Bug Reports

[ ] Test against latest release: Make sure you test against the latest released version. It is possible we already fixed the bug you're experiencing.
[ ] Search for possible duplicate reports: It's helpful to keep bug reports consolidated to one thread, so do a quick search on existing bug reports to check if anybody else has reported the same thing. You can scope searches by the label "bug" to help narrow things down.
[ ] Include steps to reproduce: Provide steps to reproduce the issue, along with your .tf files, with secrets removed, so we can try to reproduce it. Without this, it makes it much harder to fix the issue.
[ ] For panics, include crash.log: If you experienced a panic, please create a gist of the entire generated crash log for us to look at. Double check no sensitive items were in the log.

Feature Requests

[ ] Search for possible duplicate requests: It's helpful to keep requests consolidated to one thread, so do a quick search on existing requests to check if anybody else has reported the same thing. You can scope searches by the label "enhancement" to help narrow things down.
[ ] Include a use case description: In addition to describing the behavior of the feature you'd like to see added, it's helpful to also lay out the reason why the feature would be important and how it would benefit Terraform users.

Questions

[ ] Search for answers in Terraform documentation: We're happy to answer questions in GitHub Issues, but it helps reduce issue churn and maintainer workload if you work to find answers to common questions in the documentation. Often times Question issues result in documentation updates to help future users, so if you don't find an answer, you can give us pointers for where you'd expect to see it in the docs.

Issue Lifecycle

The issue is reported.
The issue is verified and categorized by a Terraform collaborator. Categorization is done via GitHub labels. We generally use a two-label system of (1) issue/PR type, and (2) section of the codebase. Type is usually "bug", "enhancement", "documentation", or "question", and section can be any of the providers or provisioners or "core".
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.
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.
The issue is closed. Sometimes, valid issues will be closed to keep the issue tracker clean. The issue is still indexed and available for future viewers, or can be re-opened if necessary.

Pull Requests

Thank you for contributing! Here you'll find information on what to include in your Pull Request to ensure it is accepted quickly.

For pull requests that follow the guidelines, we expect to be able to review and merge very quickly.
Pull requests that don't follow the guidelines will be annotated with what they're missing. A community or core team member may be able to swing around and help finish up the work, but these PRs will generally hang out much longer until they can be completed and merged.

Pull Request Lifecycle

You are welcome to submit your pull request for commentary or review before it is fully completed. Please prefix the title of your pull request with "[WIP]" to indicate this. It's also a good idea to include specific questions or items you'd like feedback on.
Once you believe your pull request is ready to be merged, you can remove any "[WIP]" prefix from the title and a core team member will review. Follow the checklists below to help ensure that your contribution will be merged quickly.
One of Terraform's core team members will look over your contribution and either provide comments letting you know if there is anything left to do. We do our best to provide feedback in a timely manner, but it may take some time for us to respond.
Once all outstanding comments and checklist items have been addressed, your contribution will be merged! Merged PRs will be included in the next Terraform release. The core team takes care of updating the CHANGELOG as they merge.
In rare cases, we might decide that a PR should be closed. We'll make sure to provide clear reasoning when this happens.

Checklists for Contribution

There are several different kinds of contribution, each of which has its own standards for a speedy review. The following sections describe guidelines for each type of contribution.

Documentation Update

Because Terraform's website is in the same repo as the code, it's easy for anybody to help us improve our docs.

[ ] Reasoning for docs update: Including a quick explanation for why the update needed is helpful for reviewers.
[ ] Relevant Terraform version: Is this update worth deploying to the site immediately, or is it referencing an upcoming version of Terraform and should get pushed out with the next release?

As mentioned above, each Terraform Provider has its own code repository in the Terraform Providers. Each repository has its own folder named website that contains that Providers documentation. Updates for documentation for a specific provider should be reported or posted there.

Enhancement/Bugfix to a Resource

Working on existing resources is a great way to get started as a Terraform contributor because you can work within existing code and tests to get a feel for what to do.

[ ] Acceptance test coverage of new behavior: Existing resources each have a set of acceptance tests covering their functionality. These tests should exercise all the behavior of the resource. Whether you are adding something or fixing a bug, the idea is to have an acceptance test that fails if your code were to be removed. Sometimes it is sufficient to "enhance" an existing test by adding an assertion or tweaking the config that is used, but often a new test is better to add. You can copy/paste an existing test and follow the conventions you see there, modifying the test to exercise the behavior of your code.
[ ] Documentation updates: If your code makes any changes that need to be documented, you should include those doc updates in the same PR. The Terraform website source is in this repo and includes instructions for getting a local copy of the site up and running if you'd like to preview your changes.
[ ] Well-formed Code: Do your best to follow existing conventions you see in the codebase, and ensure your code is formatted with go fmt. (The Travis CI build will fail if go fmt has not been run on incoming code.) The PR reviewers can help out on this front, and may provide comments with suggestions on how to improve the code.

New Resource

Implementing a new resource is a good way to learn more about how Terraform interacts with upstream APIs. There are plenty of examples to draw from in the existing resources, but you still get to implement something completely new.

[ ] Minimal LOC: It can be inefficient for both the reviewer and author to go through long feedback cycles on a big PR with many resources. We therefore encourage you to only submit 1 resource at a time.
[ ] Acceptance tests: New resources should include acceptance tests covering their behavior. See Writing Acceptance Tests below for a detailed guide on how to approach these.
[ ] Documentation: Each resource gets a page in the Terraform documentation. The Terraform website source is in this repo and includes instructions for getting a local copy of the site up and running if you'd like to preview your changes. For a resource, you'll want to add a new file in the appropriate place and add a link to the sidebar for that page.
[ ] Well-formed Code: Do your best to follow existing conventions you see in the codebase, and ensure your code is formatted with go fmt. (The Travis CI build will fail if go fmt has not been run on incoming code.) The PR reviewers can help out on this front, and may provide comments with suggestions on how to improve the code.

New Provider

Implementing a new provider gives Terraform the ability to manage resources in a whole new API. It's a larger undertaking, but brings major new functionality into Terraform.

[ ] Minimal initial LOC: Some providers may be big, and it can be inefficient for both reviewer & author to go through long feedback cycles on a big PR with many resources. We encourage you to only submit the necessary minimum in a single PR, ideally just the first resource of the provider.
[ ] Acceptance tests: Each provider should include an acceptance test suite with tests for each resource should include acceptance tests covering its behavior. See Writing Acceptance Tests below for a detailed guide on how to approach these.
[ ] Documentation: Each provider has a section in the Terraform documentation. The Terraform website source is in this repo and includes instructions for getting a local copy of the site up and running if you'd like to preview your changes. For a provider, you'll want to add new index file and individual pages for each resource.
[ ] Well-formed Code: Do your best to follow existing conventions you see in the codebase, and ensure your code is formatted with go fmt. (The Travis CI build will fail if go fmt has not been run on incoming code.) The PR reviewers can help out on this front, and may provide comments with suggestions on how to improve the code.

Core Bugfix/Enhancement

We are always happy when any developer is interested in diving into Terraform's core to help out! Here's what we look for in smaller Core PRs.

[ ] Unit tests: Terraform's core is covered by hundreds of unit tests at several different layers of abstraction. Generally the best place to start is with a "Context Test". These are higher level test that interact end-to-end with most of Terraform's core. They are divided into test files for each major action (plan, apply, etc.). Getting a failing test is a great way to prove out a bug report or a new enhancement. With a context test in place, you can work on implementation and lower level unit tests. Lower level tests are largely context dependent, but the Context Tests are almost always part of core work.
[ ] Documentation updates: If the core change involves anything that needs to be reflected in our documentation, you can make those changes in the same PR. The Terraform website source is in this repo and includes instructions for getting a local copy of the site up and running if you'd like to preview your changes.
[ ] Well-formed Code: Do your best to follow existing conventions you see in the codebase, and ensure your code is formatted with go fmt. (The Travis CI build will fail if go fmt has not been run on incoming code.) The PR reviewers can help out on this front, and may provide comments with suggestions on how to improve the code.

Core Feature

If you're interested in taking on a larger core feature, it's a good idea to get feedback early and often on the effort.

[ ] Early validation of idea and implementation plan: Terraform's core is complicated enough that there are often several ways to implement something, each of which has different implications and tradeoffs. Working through a plan of attack with the team before you dive into implementation will help ensure that you're working in the right direction.
[ ] Unit tests: Terraform's core is covered by hundreds of unit tests at several different layers of abstraction. Generally the best place to start is with a "Context Test". These are higher level test that interact end-to-end with most of Terraform's core. They are divided into test files for each major action (plan, apply, etc.). Getting a failing test is a great way to prove out a bug report or a new enhancement. With a context test in place, you can work on implementation and lower level unit tests. Lower level tests are largely context dependent, but the Context Tests are almost always part of core work.
[ ] Documentation updates: If the core change involves anything that needs to be reflected in our documentation, you can make those changes in the same PR. The Terraform website source is in this repo and includes instructions for getting a local copy of the site up and running if you'd like to preview your changes.
[ ] Well-formed Code: Do your best to follow existing conventions you see in the codebase, and ensure your code is formatted with go fmt. (The Travis CI build will fail if go fmt has not been run on incoming code.) The PR reviewers can help out on this front, and may provide comments with suggestions on how to improve the code.

Writing Acceptance Tests

Terraform includes an acceptance test harness that does most of the repetitive work involved in testing a resource.

Acceptance Tests Often Cost Money to Run

Because acceptance tests create real resources, they often cost money to run. Because the resources only exist for a short period of time, the total amount of money required is usually relatively small. Nevertheless, we don't want financial limitations to be a barrier to contribution, so if you are unable to pay to run acceptance tests for your contribution, simply mention this in your pull request. We will happily accept "best effort" implementations of acceptance tests and run them for you on our side. This might mean that your PR takes a bit longer to merge, but it most definitely is not a blocker for contributions.

Running an Acceptance Test

Acceptance tests can be run using the testacc target in the Terraform Makefile. The individual tests to run can be controlled using a regular expression. Prior to running the tests provider configuration details such as access keys must be made available as environment variables.

For example, to run an acceptance test against the Azure Resource Manager provider, the following environment variables must be set:

export ARM_SUBSCRIPTION_ID=...
export ARM_CLIENT_ID=...
export ARM_CLIENT_SECRET=...
export ARM_TENANT_ID=...

Tests can then be run by specifying the target provider and a regular expression defining the tests to run:

$ make testacc TEST=./builtin/providers/azurerm TESTARGS='-run=TestAccAzureRMPublicIpStatic_update'
==> Checking that code complies with gofmt requirements...
go generate ./...
TF_ACC=1 go test ./builtin/providers/azurerm -v -run=TestAccAzureRMPublicIpStatic_update -timeout 120m
=== RUN   TestAccAzureRMPublicIpStatic_update
--- PASS: TestAccAzureRMPublicIpStatic_update (177.48s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/azurerm    177.504s

Entire resource test suites can be targeted by using the naming convention to write the regular expression. For example, to run all tests of the azurerm_public_ip resource rather than just the update test, you can start testing like this:

$ make testacc TEST=./builtin/providers/azurerm TESTARGS='-run=TestAccAzureRMPublicIpStatic'
==> Checking that code complies with gofmt requirements...
go generate ./...
TF_ACC=1 go test ./builtin/providers/azurerm -v -run=TestAccAzureRMPublicIpStatic -timeout 120m
=== RUN   TestAccAzureRMPublicIpStatic_basic
--- PASS: TestAccAzureRMPublicIpStatic_basic (137.74s)
=== RUN   TestAccAzureRMPublicIpStatic_update
--- PASS: TestAccAzureRMPublicIpStatic_update (180.63s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/azurerm    318.392s

Writing an Acceptance Test

Terraform has a framework for writing acceptance tests which minimizes the amount of boilerplate code necessary to use common testing patterns. The entry point to the framework is the resource.Test() function.

Tests are divided into TestSteps. Each TestStep proceeds by applying some Terraform configuration using the provider under test, and then verifying that results are as expected by making assertions using the provider API. It is common for a single test function to exercise both the creation of and updates to a single resource. Most tests follow a similar structure.

Pre-flight checks are made to ensure that sufficient provider configuration is available to be able to proceed - for example in an acceptance test targeting AWS, AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY must be set prior to running acceptance tests. This is common to all tests exercising a single provider.

Each TestStep is defined in the call to resource.Test(). Most assertion functions are defined out of band with the tests. This keeps the tests readable, and allows reuse of assertion functions across different tests of the same type of resource. The definition of a complete test looks like this:

func TestAccAzureRMPublicIpStatic_update(t *testing.T) {
        resource.Test(t, resource.TestCase{
                PreCheck:     func() { testAccPreCheck(t) },
                Providers:    testAccProviders,
                CheckDestroy: testCheckAzureRMPublicIpDestroy,
                Steps: []resource.TestStep{
                        resource.TestStep{
                                Config: testAccAzureRMVPublicIpStatic_basic,
                                Check: resource.ComposeTestCheckFunc(
                                        testCheckAzureRMPublicIpExists("azurerm_public_ip.test"),
                                ),
                        },
        },
    })
}

When executing the test, the following steps are taken for each TestStep:

The Terraform configuration required for the test is applied. This is responsible for configuring the resource under test, and any dependencies it may have. For example, to test the azurerm_public_ip resource, an azurerm_resource_group is required. This results in configuration which looks like this:

resource "azurerm_resource_group" "test" {
    name = "acceptanceTestResourceGroup1"
    location = "West US"
}

resource "azurerm_public_ip" "test" {
    name = "acceptanceTestPublicIp1"
    location = "West US"
    resource_group_name = "${azurerm_resource_group.test.name}"
    public_ip_address_allocation = "static"
}

Assertions are run using the provider API. These use the provider API directly rather than asserting against the resource state. For example, to verify that the azurerm_public_ip described above was created successfully, a test function like this is used:

func testCheckAzureRMPublicIpExists(name string) resource.TestCheckFunc {
    return func(s *terraform.State) error {
        // Ensure we have enough information in state to look up in API
        rs, ok := s.RootModule().Resources[name]
        if !ok {
            return fmt.Errorf("Not found: %s", name)
        }

        publicIPName := rs.Primary.Attributes["name"]
        resourceGroup, hasResourceGroup := rs.Primary.Attributes["resource_group_name"]
        if !hasResourceGroup {
            return fmt.Errorf("Bad: no resource group found in state for public ip: %s", availSetName)
        }

        conn := testAccProvider.Meta().(*ArmClient).publicIPClient

        resp, err := conn.Get(resourceGroup, publicIPName, "")
        if err != nil {
            return fmt.Errorf("Bad: Get on publicIPClient: %s", err)
        }

        if resp.StatusCode == http.StatusNotFound {
            return fmt.Errorf("Bad: Public IP %q (resource group: %q) does not exist", name, resourceGroup)
        }

        return nil
    }
}

Notice that the only information used from the Terraform state is the ID of the resource - though in this case it is necessary to split the ID into constituent parts in order to use the provider API. For computed properties, we instead assert that the value saved in the Terraform state was the expected value if possible. The testing framework provides helper functions for several common types of check - for example:

```go
resource.TestCheckResourceAttr("azurerm_public_ip.test", "domain_name_label", "mylabel01"),
```

The resources created by the test are destroyed. This step happens automatically, and is the equivalent of calling terraform destroy.

Assertions are made against the provider API to verify that the resources have indeed been removed. If these checks fail, the test fails and reports "dangling resources". The code to ensure that the azurerm_public_ip shown above looks like this:

func testCheckAzureRMPublicIpDestroy(s *terraform.State) error {
    conn := testAccProvider.Meta().(*ArmClient).publicIPClient

    for _, rs := range s.RootModule().Resources {
        if rs.Type != "azurerm_public_ip" {
            continue
        }

        name := rs.Primary.Attributes["name"]
        resourceGroup := rs.Primary.Attributes["resource_group_name"]

        resp, err := conn.Get(resourceGroup, name, "")

        if err != nil {
            return nil
        }

        if resp.StatusCode != http.StatusNotFound {
            return fmt.Errorf("Public IP still exists:\n%#v", resp.Properties)
        }
    }

    return nil
}

These functions usually test only for the resource directly under test: we skip the check that the azurerm_resource_group has been destroyed when testing azurerm_resource_group, under the assumption that azurerm_resource_group is tested independently in its own acceptance tests.