Create a Container Action with the GitHub Actions Toolkit

Use this template to bootstrap the creation of a container action with the GitHub Actions toolkit. 🚀

This template includes compilation support, tests, a validation workflow, publishing, and versioning guidance.

For more information on the GitHub Actions toolkit, see the actions/toolkit repository

Create Your Own Action

To create your own action, you can use this repository as a template! Just follow the below instructions:

1. Click the Use this template button at the top of the repository
2. Select Create a new repository
3. Select an owner and name for your new repository
4. Click Create repository
5. Clone your new repository

Important

Make sure to remove or update the CODEOWNERS file! For details on how to use this file, see About code owners.

Initial Setup

After you've cloned the repository to your local machine or codespace, you'll need to perform some initial setup steps before you can develop your action.

Note

You'll need to have reasonably modern versions of Node.js and Docker handy (e.g. Node.js v20+ and docker engine v20+).

1. 🛠️ Install the dependencies

   npm install

2. 🏗️ Package the TypeScript for distribution

   npm run bundle

3. ✅ Run the tests

   $ npm test
   
   PASS  ./index.test.js
     ✓ throws invalid number (3ms)
     ✓ wait 500 ms (504ms)
     ✓ test runs (95ms)
   
   ...

4. 🛠️ Build the container

   Make sure to replace actions/container-toolkit-action with an appropriate label for your container.

   docker build -t actions/container-toolkit-action .

5. ✅ Test the container

   You can pass individual environment variables using the --env or -e flag.

   $ docker run --env INPUT_MILLISECONDS=2000 actions/container-toolkit-action
   ::debug::The event payload: {}
   16:19:19 GMT+0000 (Coordinated Universal Time)
   16:19:21 GMT+0000 (Coordinated Universal Time)
   
   ::set-output name=time::16:19:21 GMT+0000 (Coordinated Universal Time)

   Or you can pass a file with environment variables using --env-file.

   $ echo "INPUT_MILLISECONDS=2000" > ./.env.test
   
   $ docker run --env-file ./.env.test actions/container-toolkit-action
   ::debug::The event payload: {}
   16:19:19 GMT+0000 (Coordinated Universal Time)
   16:19:21 GMT+0000 (Coordinated Universal Time)
   
   ::set-output name=time::16:19:21 GMT+0000 (Coordinated Universal Time)

Update the Action Metadata

The action.yml file defines metadata about your action, such as input(s) and output(s). For details about this file, see Metadata syntax for GitHub Actions.

When you copy this repository, update action.yml with the name, description, inputs, and outputs for your action.

Update the Action Code

Update the TypeScript Source

The src/ directory is the heart of your action! This contains the source code that will be run when your action is invoked. You can replace the contents of this directory with your own code.

There are a few things to keep in mind when writing your action code:

• Most GitHub Actions toolkit and CI/CD operations are processed asynchronously. In main.ts, you will see that the action is run in an async function.

  import * as core from '@actions/core'
  //...
  
  export async function run(): Promise<void> {
    try {
      //...
    } catch (error) {
      core.setFailed(error.message)
    }
  }

  For more information about the GitHub Actions toolkit, see the documentation.

Update the Container

In this template, the container action runs a Node.js script, node /dist/index.js, when the container is launched. Since you can choose any base Docker image and language you like, you can change this to suite your needs. There are a few main things to remember when writing code for container actions:

• Inputs are accessed using argument identifiers or environment variables (depending on what you set in your action.yml). For example, the first input to this action, milliseconds, can be accessed in the Node.js script using the process.env.INPUT_MILLISECONDS environment variable or the getInput('milliseconds') function from the @actions/core library.

  // Use an action input
  const ms: number = parseInt(core.getInput('milliseconds'), 10)
  
  // Use an environment variable
  const ms: number = parseInt(process.env.INPUT_MILLISECONDS, 10)

• GitHub Actions supports a number of different workflow commands such as creating outputs, setting environment variables, and more. These are accomplished by writing to different GITHUB_* environment variables. For more information, see Commands.

  Scenario	Example
  Set environment vars	core.exportVariable('MY_VAR', 'my-value')
  Set outputs	core.setOutput('time', new Date().toTimeString())
  Set secrets	core.setSecret('mySecret')
  Prepend to PATH	core.addPath('/usr/local/bin')

Publish the Action

So, what are you waiting for? Go ahead and start customizing your action!

1. Create a new branch

   git checkout -b releases/v1

2. Replace the contents of src/ with your action code

3. Add tests to __tests__/ for your source code

4. Format, test, and build the action

   npm run all

   [!WARNING]

   This step is important! It will run ncc to build the final JavaScript action code with all dependencies included. If you do not run this step, your action will not work correctly when it is used in a workflow. This step also includes the --license option for ncc, which will create a license file for all of the production node modules used in your project.

5. Commit your changes

   git add .
   git commit -m "My first action is ready!"

6. Push them to your repository

   git push -u origin releases/v1

7. Create a pull request and get feedback on your action

8. Merge the pull request into the main branch

Your action is now published! 🚀

For information about versioning your action, see Versioning in the GitHub Actions toolkit.

Validate the Action

You can now validate the action by referencing it in a workflow file. For example, ci.yml demonstrates how to reference an action in the same repository.

steps:
  - name: Checkout
    id: checkout
    uses: actions/checkout@v4

  - name: Test Local Action
    id: test-action
    uses: ./
    with:
      milliseconds: 1000

  - name: Print Output
    id: output
    run: echo "${{ steps.test-action.outputs.time }}"

For example workflow runs, check out the Actions tab! :rocket:

Usage

After testing, you can create version tag(s) that developers can use to reference different stable versions of your action. For more information, see Versioning in the GitHub Actions toolkit.

To include the action in a workflow in another repository, you can use the uses syntax with the @ symbol to reference a specific branch, tag, or commit hash.

steps:
  - name: Checkout
    id: checkout
    uses: actions/checkout@v4

  - name: Test Local Action
    id: test-action
    uses: actions/container-toolkit-action@v1 # Commit with the `v1` tag
    with:
      milliseconds: 1000

  - name: Print Output
    id: output
    run: echo "${{ steps.test-action.outputs.time }}"