cfnfmt

:construction: WORK IN PROGRESS

cfnfmt is an AWS CloudFormation template style formatter. It identifies and corrects things like line spacing, key ordering and other items which could be considered personal preference whilst preserving comments.

It does not check or determine the validity of resource property syntax, for that you should use cfn-lint.

Installation

npm i -g cfnfmt

Usage

Basic usage:

cfnfmt template.yml other-template.yaml

You can also format all templates in a whole directory:

cfnfmt .

Configuration

cfnfmt uses a set of rules to allow you to customize your template styling preference. Each rule is independent from the others, and can be enabled, disabled or changed. All these settings can be gathered in a configuration file.

To use a custom configuration file, use the -c option:

cfnfmt -c config.yaml template.yaml

If -c is not provided, cfnfmt will look for a configuration file in the following locations (by order of preference):

• .cfnfmt, .cfnfmt.yaml or .cfnfmt.yml in the current working directory
• the file referenced by $CFNFMT_CONFIG_FILE, if set
• ~/.config/cfnfmt/config

Finally, if no config file is found the default configuration is applied.

Default Configuration

template-filenames:
- "*.yaml"
- "*.yml"
- "*.template"
rules:
  aws-template-format-version: true
  key-indent-level: 2
  section-order:
  - "AWSTemplateFormatVersion"
  - "Description"
  - "Metadata"
  - "Parameters"
  - "Mappings"
  - "Conditions"
  - "Transform"
  - "Resources"
  - "Outputs"
  resource-key-order:
  - "DependsOn"
  - "Condition"
  - "CreationPolicy"
  - "UpdatePolicy"
  - "UpdateReplacePolicy"
  - "DeletionPolicy"
  - "Type"
  - "Metadata"
  - "Properties"

When specifying configuration with the -c option, the default configuration values are used for any values not explicitly defined.

Template Filenames

You may set the matchable filenames using the template-filenames property within the configuration file. This property will only be considered if the input path is a directory. Files that do not contain a Resources key will be skipped.

Rules

The following settings can be set in the rules section of the configuration file:

aws-template-format-version

If set to true, the template is checked for the presence of the AWSTemplateFormatVersion key. If not found, the key will be added with the 2010-09-09 value.

key-indent-level

An integer representing the number of spaces to indent map/object keys at, relative to its parent key. Lists/sequences are not affected by this setting. Set to false to ignore key indenting.

section-order

A list of sections in the order it should be rearranged to. Not all defined sections have to be defined in the template. Any sections not defined by this list will retain their existing order. Set to false to retain existing order.

resource-key-order

A list of keys in the order they should be rearranged to within resources. Not all defined keys have to be defined in the resource. Any keys not defined by this list will retain their existing order. Set to false to retain existing order.

new-lines-at-end-of-file

An integer representing the desired number of newlines at the end of the file (usually set to 0 or 1). Defaults to 1.