Tf Rules

The Tf rules are useful to validate, lint and format terraform code.

They can typically be used in a terraform monorepo of modules to lint, run validation tests, auto generate documentation and enforce the consistency of providers versions across all modules.

Why "Tf" and not "Terraform"

Because now you can either use "tofu" or "terraform" binary.

Getting Started

To import rules_tf in your project, you first need to add it to your MODULE.bazel file:

bazel_dep(name = "rules_tf", version = "0.0.6")
# git_override(
#     module_name = "rules_tf",
#     remote      = "https://github.com/yanndegat/rules_tf",
#     commit      = "...",
# )

tf = use_extension("@rules_tf//tf:extensions.bzl", "tf_repositories", dev_dependency = True)
tf.download( 
    version = "1.5.7", 
    use_tofu = False,
    versions = {
        "random" : "hashicorp/random:3.3.2",
        "null"   : "hashicorp/null:3.1.1",
    } 
)

# Switch to tofu
# tf = use_extension("@rules_tf//tf:extensions.bzl", "tf_repositories")
# tf.download( 
#    version = "1.6.0", 
#    use_tofu = True,
#    mirror = {
#        "random" : "hashicorp/random:3.3.2",
#        "null"   : "hashicorp/null:3.1.1",
#    }
# )

use_repo(tf, "tf_toolchains")
register_toolchains(
    "@tf_toolchains//:all",
    dev_dependency = True,
)

Once you've imported the rule set , you can then load the tf rules in your BUILD files with:

load("@rules_tf//tf:def.bzl", "tf_providers_versions", "tf_module")

tf_providers_versions(
    name = "providers",
    tf_version = "1.2.3",
    providers = {
        "random" : "hashicorp/random:>=3.3",
        "null"   : "hashicorp/null:>=3.1",
    },
)

tf_module(
    name = "root-mod-a",
    providers = [
        "random",
    ],
    deps = [
        "//tf/modules/mod-a",
    ],
    providers_versions = ":providers",
)

Using Tf Modules

1. Using custom tflint config file

load("@rules_tf//tf:def.bzl", "tf_module")

filegroup(
    name = "tflint-custom-config",
    srcs = [
        "my-tflint-config.hcl",
    ],
)

tf_module(
    name = "mod-a",
    providers = [
        "random",
    ],
    ...
    tflint_config = ":tflint-custom-config"
    
)

1. Generating versions.tf.json files

Terraform linter by default requires that all providers used by a module are versioned. It is possible to generate a versions.tf.json file by running a dedicated target:

load("@rules_tf//tf:def.bzl", "tf_providers_versions", "tf_module")

tf_providers_versions(
    name = "providers",
    tf_version = "1.2.3",
    providers = {
        "random" : "hashicorp/random:3.3.2",
        "null"   : "hashicorp/null:3.1.1",
    },
)

tf_module(
    name = "root-mod-a",
    providers = [
        "random",
    ],
    deps = [
        "//tf/modules/mod-a",
    ],
    
    providers_versions = ":providers",
)

bazel run //path/to/root-mod-a:gen-tf-versions

or generate all files of a workspace:

bazel cquery 'kind(tf_gen_versions, //...)' --output files | xargs -n1 bash

1. Generating terraform doc files

It is possible to generate a README.md file by running a dedicated target for terraform modules:

load("@rules_tf//tf:def.bzl", "tf_gen_doc")

tf_gen_doc(
    name = "tfgendoc",
    modules = ["//{}/{}".format(package_name(), m) for m in subpackages(include = ["**/*.tf"])],
)

and run the following command to generate docs for all sub packages.

bazel run //path/to:tfgendoc

It is also possible to customize terraform docs config:

load("@rules_tf//tf:def.bzl", "tf_gen_doc")

filegroup(
    name = "tfdoc-config",
    srcs = [
        "my-tfdoc-config.yaml",
    ],
)

tf_gen_doc(
    name   = "custom-tfgendoc",
    modules = ["//{}/{}".format(package_name(), m) for m in subpackages(include = ["**/*.tf"])],
    config = ":tfdoc-config",
)

1. Formatting terraform files

It is possible to format terraform files by running a dedicated target:

load("@rules_tf//tf:def.bzl", "tf_format")


tf_format(
    name = "tffmt",
    modules = ["//{}/{}".format(package_name(), m) for m in subpackages(include = ["**/*.tf"])],
)

and run the following command to generate docs for all sub packages.

bazel run //path/to:tffmt