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Contributing to Terraform

This repository contains only Terraform core, which includes the command line interface and the main graph engine. Providers are implemented as plugins that each have their own repository in the terraform-providers organization on GitHub. Instructions for developing each provider are in the associated README file. For more information, see the provider development overview.

Terraform is an open source project and we appreciate contributions of various kinds, including bug reports and fixes, enhancement proposals, documentation updates, and user experience feedback.

To record a bug report, enhancement proposal, or give any other product feedback, please open a GitHub issue using the most appropriate issue template. Please do fill in all of the information the issue templates request, because we've seen from experience that this will maximize the chance that we'll be able to act on your feedback.

Please note that we don't use GitHub issues for usage questions. If you have a question about how to use Terraform in general or how to solve a specific problem with Terraform, please start a topic in the Terraform community forum, where both Terraform team members and community members participate in discussions.

All communication on GitHub, the community forum, and other HashiCorp-provided communication channels is subject to the HashiCorp community guidelines.

Terraform CLI/Core Development Environment

This repository contains the source code for Terraform CLI, which is the main component of Terraform that contains the core Terraform engine.

The HashiCorp-maintained Terraform providers are also open source but are not in this repository; instead, they are each in their own repository in the terraform-providers organization on GitHub.

This repository also does not include the source code for some other parts of the Terraform product including Terraform Cloud, Terraform Enterprise, and the Terraform Registry. Those components are not open source, though if you have feedback about them (including bug reports) please do feel free to open a GitHub issue on this repository.

If you wish to work on the Terraform CLI source code, you'll first need to install the Go compiler and the version control system Git.

At this time the Terraform development environment is targeting only Linux and Mac OS X systems. While Terraform itself is compatible with Windows, unfortunately the unit test suite currently contains Unix-specific assumptions around maximum path lengths, path separators, etc.

Refer to the file .go-version to see which version of Go Terraform is currently built with. Other versions will often work, but if you run into any build or testing problems please try with the specific Go version indicated. You can optionally simplify the installation of multiple specific versions of Go on your system by installing goenv, which reads .go-version and automatically selects the correct Go version.

Use Git to clone this repository into a location of your choice. Terraform is using Go Modules, and so you should not clone it inside your GOPATH.

Switch into the root directory of the cloned repository and build Terraform using the Go toolchain in the standard way:

cd terraform
go install .

The first time you run the go install command, the Go toolchain will download any library dependencies that you don't already have in your Go modules cache. Subsequent builds will be faster because these dependencies will already be available on your local disk.

Once the compilation process succeeds, you can find a terraform executable in the Go executable directory. If you haven't overridden it with the GOBIN environment variable, the executable directory is the bin directory inside the directory returned by the following command:

go env GOPATH

If you are planning to make changes to the Terraform source code, you should run the unit test suite before you start to make sure everything is initially passing:

go test ./...

As you make your changes, you can re-run the above command to ensure that the tests are still passing. If you are working only on a specific Go package, you can speed up your testing cycle by testing only that single package, or packages under a particular package prefix:

go test ./command/...
go test ./addrs

Acceptance Tests: Testing interactions with external services

Terraform's unit test suite is self-contained, using mocks and local files to help ensure that it can run offline and is unlikely to be broken by changes to outside systems.

However, several Terraform components interact with external services, such as the automatic provider installation mechanism, the Terraform Registry, Terraform Cloud, etc.

There are some optional tests in the Terraform CLI codebase that do interact with external services, which we collectively refer to as "acceptance tests". You can enable these by setting the environment variable TF_ACC=1 when running the tests. We recommend focusing only on the specific package you are working on when enabling acceptance tests, both because it can help the test run to complete faster and because you are less likely to encounter failures due to drift in systems unrelated to your current goal:

TF_ACC=1 go test ./internal/initwd

Because the acceptance tests depend on services outside of the Terraform codebase, and because the acceptance tests are usually used only when making changes to the systems they cover, it is common and expected that drift in those external systems will cause test failures. Because of this, prior to working on a system covered by acceptance tests it's important to run the existing tests for that system in an unchanged work tree first and respond to any test failures that preexist, to avoid misinterpreting such failures as bugs in your new changes.

Generated Code

Some files in the Terraform CLI codebase are generated. In most cases, we update these using go generate, which is the standard way to encapsulate code generation steps in a Go codebase.

go generate ./...

Use git diff afterwards to inspect the changes and ensure that they are what you expected.

Terraform includes generated Go stub code for the Terraform provider plugin protocol, which is defined using Protocol Buffers. Because the Protocol Buffers tools are not written in Go and thus cannot be automatically installed using go get, we follow a different process for generating these, which requires that you've already installed a suitable version of protoc:

make protobuf

External Dependencies

Terraform uses Go Modules for dependency management, but currently uses "vendoring" to include copies of all of the external library dependencies in the Terraform repository to allow builds to complete even if third-party dependency sources are unavailable.

Our dependency licensing policy for Terraform excludes proprietary licenses and "copyleft"-style licenses. We accept the common Mozilla Public License v2, MIT License, and BSD licenses. We will consider other open source licenses in similar spirit to those three, but if you plan to include such a dependency in a contribution we'd recommend opening a GitHub issue first to discuss what you intend to implement and what dependencies it will require so that the Terraform team can review the relevant licenses to for whether they meet our licensing needs.

If you need to add a new dependency to Terraform or update the selected version for an existing one, use go get from the root of the Terraform repository as follows:

go get github.com/hashicorp/hcl/v2@2.0.0

This command will download the requested version (2.0.0 in the above example) and record that version selection in the go.mod file. It will also record checksums for the module in the go.sum.

To complete the dependency change, clean up any redundancy in the module metadata files and resynchronize the vendor directory with the new package selections by running the following commands:

go mod tidy
go mod vendor

To ensure that the vendoring has worked correctly, be sure to run the unit test suite at least once in vendoring mode, where Go will use the vendored dependencies to build the test programs:

go test -mod=vendor ./...

Because dependency changes affect a shared, top-level file, they are more likely than some other change types to become conflicted with other proposed changes during the code review process. For that reason, and to make dependency changes more visible in the change history, we prefer to record dependency changes as separate commits that include only the results of the above commands and the minimal set of changes to Terraform's own code for compatibility with the new version:

git add go.mod go.sum vendor
git commit -m "vendor: go get github.com/hashicorp/hcl/v2@2.0.0"

You can then make use of the new or updated dependency in new code added in subsequent commits.

Proposing a Change

If you'd like to contribute a code change to Terraform, we'd love to review a GitHub pull request.

In order to be respectful of the time of community contributors, we prefer to discuss potential changes in GitHub issues prior to implementation. That will allow us to give design feedback up front and set expectations about the scope of the change, and, for larger changes, how best to approach the work such that the Terraform team can review it and merge it along with other concurrent work.

If the bug you wish to fix or enhancement you wish to implement isn't already covered by a GitHub issue that contains feedback from the Terraform team, please do start a discussion (either in a new GitHub issue or an existing one, as appropriate) before you invest significant development time. If you mention your intent to implement the change described in your issue, the Terraform team can prioritize including implementation-related feedback in the subsequent discussion.

At this time, we do not have a formal process for reviewing outside proposals that significantly change Terraform's workflow, its primary usage patterns, and its language. While we do hope to put such a thing in place in the future, we wish to be up front with potential contributors that unfortunately we are unlikely to be able to give prompt feedback for large proposals that could entail a significant design phase, though we are still interested to hear about your use-cases so that we can consider ways to meet them as part of other larger projects.

Most changes will involve updates to the test suite, and changes to Terraform's documentation. The Terraform team can advise on different testing strategies for specific scenarios, and may ask you to revise the specific phrasing of your proposed documentation prose to match better with the standard "voice" of Terraform's documentation.

This repository is primarily maintained by a small team at HashiCorp along with their other responsibilities, so unfortunately we cannot always respond promptly to pull requests, particularly if they do not relate to an existing GitHub issue where the Terraform team has already participated. We are grateful for all contributions however, and will give feedback on pull requests as soon as we're able.

PR Checks

The following checks run when a PR is opened:

Contributor License Agreement (CLA): If this is your first contribution to Terraform you will be asked to sign the CLA.
Tests: tests include unit tests and acceptance tests, and all tests must pass before a PR can be merged.
Test Coverage Report: We use codecov to check both overall test coverage, and patch coverage.

-> Note: We are still deciding on the right targets for our code coverage check. A failure in codecov does not necessarily mean that your PR will not be approved or merged.

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