atmos aws cloudformation fmt

Format the component's local template in place: a dependency-free, native round-trip through the YAML parser that re-serializes the template with consistent indentation, preserving comments and key order. There is no cfn-format binary to shell out to (Rain's own formatter is archived along with the rest of Rain), so this is entirely native.

Experimental

atmos aws cloudformation fmt --help

Usage

atmos aws cloudformation fmt <component> --stack <stack> [options]

atmos aws cloudformation fmt vpc -s plat-ue2-dev

Check whether the template is formatted without writing changes (for CI):

atmos aws cloudformation fmt vpc -s plat-ue2-dev --check

Format all or affected components' templates in dependency order:

atmos aws cloudformation fmt --all -s plat-ue2-dev
atmos aws cloudformation fmt --affected --base origin/main --check

Check mode

With --check, fmt reports each template and never writes:

• A template that is already formatted prints already formatted.
• An unformatted template prints not formatted; a single-component run then exits non-zero.
• With --all, --affected, --tags, or --labels, fmt --check checks every selected template and prints a line for each one, then exits non-zero once at the end, with an error that lists every unformatted template. It does not stop at the first one.

Components that point at the same template file share one check, identified by the file's resolved path, so a shared template is reported once per run rather than once per component.

Flags

--stack, -s (required for a single component)

Atmos stack. Required when operating on a single component; optional (and used only to narrow the selected set) with --all/--affected.

--check (optional)

Report whether the template is formatted without writing changes. Exits non-zero if the template is not formatted — use this in CI instead of the default write-in-place behavior.

--all (optional)

Process all aws/cloudformation components in dependency order.

--affected (optional)

Process affected aws/cloudformation components and their dependencies. Compares the working tree against a base: see --base and the Git flags below.

--include-dependents (optional)

With --affected, include dependent aws/cloudformation components.

--base (optional)

Git base ref or SHA to compare against for affected detection: --base=origin/main. A value that looks like a commit SHA is treated as --sha, anything else as --ref. Used with --affected.

--tags (optional)

Filter by tags (comma-separated, matches any): --tags=production,tier-1. Composes with --all/--affected to narrow the selected set further; cannot be combined with a single component argument.

--labels (optional)

Filter by labels (repeatable and/or comma-separated key=value or key:value pairs, matches all): --labels=cost-center=platform,compliance=sox. Composes with --all/--affected/--tags; cannot be combined with a single component argument.

--ci (optional)

Enable native CI integration (requires ci.enabled): writes the job summary and output variables for the operation. Also enabled by the CI and ATMOS_CI environment variables.

--ref (optional)

Git ref to compare against for affected detection. Used with --affected.

--sha (optional)

Git SHA to compare against for affected detection. Used with --affected.

--repo-path (optional)

Path to an already cloned target repository to use as the affected baseline. Used with --affected.

--clone-target-ref (optional)

Clone the target ref instead of checking it out in the current repository for affected detection. Used with --affected.

--ssh-key (optional)

Path to the SSH private key used to clone the target ref for affected detection. Used with --clone-target-ref.

--ssh-key-password (optional)

Password for the SSH private key used to clone the target ref for affected detection. Used with --clone-target-ref.

note

fmt never calls the CloudFormation API and does not fire before/after hook events — only apply, diff, delete, drift detect, and drift describe do.