tofu-fmt

tofu fmt is the built-in OpenTofu command that rewrites configuration files to a canonical format and style. OpenTofu is the community-driven, MPL-2.0 licensed fork of Terraform hosted by the Linux Foundation, and its formatter follows the same canonical style as terraform fmt.

Key Features:

Official Formatter: Built into OpenTofu core, so formatting always matches the version of OpenTofu you run
Open Source: OpenTofu stays under the MPL-2.0 license, unlike Terraform which moved to BUSL-1.1
Canonical Formatting: Applies consistent indentation, spacing and alignment across all configuration files
Broad File Coverage: Formats configuration (.tf), variables (.tfvars) and test (.tftest.hcl) files
Automatic Fixing: Rewrites files in place when APPLY_FIXES is enabled
Diff Mode: Shows the formatting changes it would make, so reviews stay readable
Zero Configuration: Intentionally opinionated, with no configuration or ignore file to maintain

Analyzed files

By default this linter only analyzes .tofu files, the OpenTofu specific extension that Terraform does not recognize. .tf files are left to terraform fmt, so both formatters can stay enabled without doing the same work twice.

Formatting .tf files with OpenTofu

If your project runs OpenTofu and keeps its configuration in .tf files, point this linter at them and disable the Terraform one, so a single formatter owns them:

TERRAFORM_TOFU_FMT_FILE_EXTENSIONS: [".tofu", ".tf", ".tfvars"]
DISABLE_LINTERS: [TERRAFORM_TERRAFORM_FMT]

tofu fmt also formats .tftest.hcl and .tofutest.hcl test files. They are not analyzed by default because the .hcl extension is already claimed by terragrunt in this descriptor: add them to TERRAFORM_TOFU_FMT_FILE_EXTENSIONS only if you also disable TERRAFORM_TERRAGRUNT, or you would format them twice.

tofu-fmt documentation

Version in MegaLinter: 1.12.6
Visit Official Web Site
See How to configure tofu-fmt rules

Configuration in MegaLinter

Enable tofu-fmt by adding TERRAFORM_TOFU_FMT in ENABLE_LINTERS variable
Disable tofu-fmt by adding TERRAFORM_TOFU_FMT in DISABLE_LINTERS variable

Enable autofixes by adding TERRAFORM_TOFU_FMT in APPLY_FIXES variable

Variable	Description	Default value
TERRAFORM_TOFU_FMT_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
TERRAFORM_TOFU_FMT_COMMAND_REMOVE_ARGUMENTS	User custom arguments to remove from command line before calling the linter Ex: `-s --foo "bar"`
TERRAFORM_TOFU_FMT_FILTER_REGEX_INCLUDE	Custom regex including filter Ex: `(src\\|lib)`	Exclude no file
TERRAFORM_TOFU_FMT_FILTER_REGEX_EXCLUDE	Custom regex excluding filter Ex: `(test\\|examples)`	Exclude no file
TERRAFORM_TOFU_FMT_CLI_LINT_MODE	Override default CLI lint mode - `list_of_files`: Call the linter with the list of files as argument	`list_of_files`
TERRAFORM_TOFU_FMT_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".tofu"]`
TERRAFORM_TOFU_FMT_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
TERRAFORM_TOFU_FMT_PRE_COMMANDS	List of bash commands to run before the linter	None
TERRAFORM_TOFU_FMT_POST_COMMANDS	List of bash commands to run after the linter	None
TERRAFORM_TOFU_FMT_UNSECURED_ENV_VARIABLES	List of env variables explicitly not filtered before calling TERRAFORM_TOFU_FMT and its pre/post commands	None
TERRAFORM_TOFU_FMT_DISABLE_ERRORS	Run linter but consider errors as warnings	`true`
TERRAFORM_TOFU_FMT_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`
TERRAFORM_TOFU_FMT_TIMEOUT_SECONDS	Maximum duration in seconds of the linter run, after which the linter process and its child processes are killed and reported as an error (exit code 124). Overrides LINTER_TIMEOUT_SECONDS. 0 disables the timeout	`300`
TERRAFORM_TOFU_FMT_CLI_EXECUTABLE	Override CLI executable	`['tofu']`

IDE Integration

Use tofu-fmt in your favorite IDE to catch errors before MegaLinter !

	IDE	Extension Name	Install
	IDEA	Terraform and HCL
	Visual Studio Code	OpenTofu

MegaLinter Flavors

This linter is available in the following flavors

Flavor	Description	Embedded linters
all	Default MegaLinter Flavor	132
cupcake	MegaLinter for the most commonly used languages	99
formatters	Contains only formatters	20
terraform	Optimized for TERRAFORM based projects	57

Behind the scenes

How are identified applicable files

File extensions: .tofu

How the linting is performed

tofu-fmt is called once with the list of files as arguments (list_of_files CLI lint mode)

Example calls

tofu fmt -diff -check myfile.tf

tofu fmt myfile.tf

Help content

Usage: tofu [global options] <subcommand> [args]

The available commands for execution are listed below.
The primary workflow commands are given first, followed by
less common or more advanced commands.

Main commands:
  init          Prepare your working directory for other commands
  validate      Check whether the configuration is valid
  plan          Show changes required by the current configuration
  apply         Create or update infrastructure
  destroy       Destroy previously-created infrastructure

All other commands:
  console       Try OpenTofu expressions at an interactive command prompt
  fmt           Reformat your configuration in the standard style
  force-unlock  Release a stuck lock on the current workspace
  get           Install or upgrade remote OpenTofu modules
  graph         Generate a Graphviz graph of the steps in an operation
  import        Associate existing infrastructure with a OpenTofu resource
  login         Obtain and save credentials for a remote host
  logout        Remove locally-stored credentials for a remote host
  metadata      Metadata related commands
  output        Show output values from your root module
  providers     Show the providers required for this configuration
  refresh       Update the state to match remote systems
  show          Show the current state or a saved plan
  state         Advanced state management
  taint         Mark a resource instance as not fully functional
  test          Execute integration tests for OpenTofu modules
  untaint       Remove the 'tainted' state from a resource instance
  version       Show the current OpenTofu version
  workspace     Workspace management

Global options (use these before the subcommand, if any):
  -chdir=DIR    Switch to a different working directory before executing the
                given subcommand.
  -help         Show this help output, or the help for a specified subcommand.
  -version      An alias for the "version" subcommand.

Installation on mega-linter Docker image

Dockerfile commands :

# renovate: datasource=docker depName=ghcr.io/opentofu/opentofu
ARG TERRAFORM_TOFU_FMT_VERSION=1.12.6-minimal
FROM ghcr.io/opentofu/opentofu:${TERRAFORM_TOFU_FMT_VERSION} AS opentofu
COPY --link --from=opentofu /usr/local/bin/tofu /usr/bin/