Rules for applying TF (Terraform / Tofu) modules using Bazel

This module provides rules to initialize, plan, and apply Terraform modules using Bazel. This effectively enables using tools like bazel-diff to selectively apply changes to Terraform modules only when necessary.

Usage

This depends on the rules_tf module, which provides the necessary toolchain and providers for Terraform.

# MODULE.bazel

bazel_dep(name = "rules_tf_apply", version = "0.1.0")
bazel_dep(name = "rules_tf", version = "0.0.10")

tf = use_extension("@rules_tf//tf:extensions.bzl", "tf_repositories", dev_dependency = True)
tf.download(
    mirror = {
        "random": "hashicorp/random:3.3.2",
        "null": "hashicorp/null:3.1.1",
        "aws": "hashicorp/aws:>=5.0.0",
    },
    tfdoc_version = "0.19.0",
    tflint_version = "0.53.0",
    use_tofu = False,
    version = "1.12.2",
)
use_repo(tf, "tf_toolchains")

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

and on the BUILD.bazel file:

# BUILD.bazel

load("@rules_tf_apply//tf_apply:defs.bzl", "tf_module")

tf_module(
    name = "my_tf_module",
    providers = [
        "aws",
    ],
    providers_versions = ":providers",
    tags = [
        "terraform",
    ],
    deps = [
        "//:my_other_module",
    ],
)

Running bazel run //:my_tf_module.init, plan, or apply would generate bazel-tf directory at the root of the workspace that must be gitignored. This directory contains the Terraform state and plan files generated by each of the phases.

Passing Additional Arguments

You can pass additional Terraform arguments using Bazel's -- syntax:

# Target specific resources
bazel run //:my_tf_module.plan -- --target module.web --target module.api

# Apply with additional flags  
bazel run //:my_tf_module.apply -- --target module.database -auto-approve

# Plan with custom options
bazel run //:my_tf_module.plan -- -refresh=false -parallelism=10

Any arguments passed after -- are forwarded directly to the underlying Terraform command.