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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 not 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.
However, code generation often relies on external tools which must be correctly
installed before running go generate. Terraform's Makefile includes
a target to install the tools needed for go generate:
make tools
After the tools are installed successfully, you can run code generation for all packages:
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.