GitHub Action for CloudFormation Linter

This Action for CloudFormation Linter enables arbitrary actions for interacting with CloudFormation Linter to validate CloudFormation yaml/json templates against the CloudFormation spec and additional checks. Includes checking valid values for resource properties and best practices.

The Action's primary purpose is to set the CloudFormation Linter to the runner's $PATH so you can access the linter throughout the workflow, and use in a way that suits your application. There is a way to run a CloudFormation Linter command in this workflow though if you like.

On a pull request, once this GitHub Action is set-up, it may look something like this:

Usage

There are multiple ways to consume this GitHub Action.

The recommended approach would be to to use this action to add the CloudFormation Linter to the runners $PATH and run commands throughout the rest of the workflow. An example of that can be found below:

name: Lint CloudFormation Templates

on: [push]

jobs:
  cloudformation-linter:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Setup Cloud Formation Linter with Latest Version
        uses: scottbrenner/cfn-lint-action@v2

      - name: Print the Cloud Formation Linter Version & run Linter.
        run: |
          cfn-lint --version
          cfn-lint -t ./template.yml

Within the run | section, you specify the required Cloud Formation Linter commands.

However, if you would rather run the CloudFormation Linter commands within this action. That is also possible. An example of that can be found below:

name: Lint CloudFormation Templates

on: [push]

jobs:
  cloudformation-linter:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Testing with CFN Lint Command
        uses: scottbrenner/cfn-lint-action@v2
        with:
          command: cfn-lint -t ./template.yml

Further, you can configure this action to download a specific version of the CloudFormation Linter, as well as the Python interpreter. See the table below for all the INPUTS this action can take.

Input Name	Input Description	Default Value	Required?
version	Version of CFN PyPi Package	Latest Version of CFN PyPi Package	false
python	Python Version	Defaults to python on Windows, and python3 otherwise.	false
command	Cloud Formation Linter Command to Run After Install	N/A	false

This GitHub Action does not directly output any values.

How to use the CloudFormation Linter?

See Cloud Formation Linter Usage for full usage details.

Upgrading from Version 1?

The main difference between Version 1 and Version 2 is the fact that Version 2 by default doesn't run any linting commands. The primary purpose of this action is now to provide the underlying CloudFormation Linter package and enable you to run your commands. To upgrade from Version 1 to Version 2, follow the steps below:

Step One

Change the action in your Workflow to be:

- name: Setup Cloud Formation Linter with Latest Version
  uses: scottbrenner/cfn-lint-action@v2

Step Two

If you are linting multiple files, you must enable globbing:

- name: Print the Cloud Formation Linter Version & run Linter.
  run: |
    shopt -s globstar # enable globbing
    cfn-lint --version
    cfn-lint -t ./**/*.yaml

However, if you are not linting multiple files, you can simply do:

- name: Print the Cloud Formation Linter Version & run Linter.
  run: |
    cfn-lint --version
    cfn-lint -t ./template.yaml

This should give you the same experience as before.

Development

This is a JavaScript GitHub Action that relies on Node for third party packages, and can be developed locally or in GitHub Codespaces.

Running Locally

To get this working on your local machine, firstly make sure you have a working NodeJS runtime. It is also recommended to use Act to test & run actions locally. These instructions assume you have the GitHub CLI installed.

1. Firstly, fork the repository by running:

gh repo fork ScottBrenner/cfn-lint-action

2. Install dependencies

npm install

3. To run the action locally run the following command

node index.js

GitHub Codespaces

The default Codespace configuration automatically installs and configures all dependencies necessary for development of this project.

Contributing

Please see CONTRIBUTING.md for guidelines on how to contribute to this project.

License

Please see the LICENSE.