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Creating and Publishing a Custom GitHub Action

Github Repo Link

GitHub Actions enables workflow automation within repositories, allowing developers to build, test, and deploy applications efficiently. This guide provides a step-by-step approach to creating a custom GitHub Action, testing it locally, and publishing it to the GitHub Marketplace.

Step 1: Setting Up a Custom GitHub Action

Start by creating a new repository on GitHub to store the action. Inside the repository, maintain the following folder structure:

├── .github
│   └── workflows
│       └── greet-action.yml
├── action.yml
├── Dockerfile
├── entrypoint.sh
└── README.md

Defining the Action

Every GitHub Action requires a metadata file action.yml to define its behavior:

name: "Greet Action"
description: "A GitHub Action that prints a personalized greeting message."
author: "Safeer S"
branding:
  icon: "activity"
  color: "blue"
inputs:
  message:
    description: "The message to display in logs"
    required: true
  name:
    description: "The recipient's name."
    required: true
runs:
  using: "docker"
  image: "Dockerfile"
  args:
    - ${{ inputs.name }}
    - ${{ inputs.message }}

This configuration defines essential metadata, including the action's name, description, and author details. It accepts two required input parameters: message and name. The message input specifies the text to be displayed in the logs, while name represents the recipient. The action runs inside a custom Docker container, as specified by the Dockerfile, and passes the inputs as arguments during execution. Branding details enhance visibility when published to the GitHub Marketplace.

Writing the Dockerfile

FROM alpine:3.18.3
# Default Environment Variables
ENV GITHUB_REPOSITORY=${GITHUB_REPOSITORY}
ENV GITHUB_SHA=${GITHUB_SHA}
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh  
ENTRYPOINT ["/entrypoint.sh"]

This configuration utilizes a minimal Alpine image, ensuring a lightweight runtime. It sets necessary GitHub environment variables and designates entrypoint.sh as the execution script. The script is responsible for executing the action logic:

The Entrypoint Script

#!/bin/sh
set -eo pipefail
# $1 - First argument (name)
# $2 - Second argument (message)
echo "Hello, $1! $2"

This script takes two arguments: a name and a message. The script then prints a personalized greeting using these inputs, forming the core functionality of the action.

Testing the Action

To test our Action, we define greet-action.yml inside .github/workflows/

name: greet-action
on:
  workflow_dispatch:
jobs:
  greet:
    name: "Test: Greet Action"
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v3
      - name: Run Greet Action
        uses: ./
        with:
          name: "Safeer"
          message: "Welcome to GitHub Actions!"

This workflow tests the Greet Action by invoking it with predefined inputs by using a local reference.

Go to GitHub Actions, select "Greet Action," and click "Run Workflow."

After execution, navigate to the logs to verify the output message.

Step 2: Publishing to the GitHub Marketplace

To make the Action publicly available, open GitHub Marketplace and select "Create a new extension."

Choose the action created earlier and click "Publish Action."

Draft a new release

Check the "Publish this release to GitHub Marketplace" option, ensure all requirements are met, select appropriate categories, and proceed with publishing.

Before that, accept the GitHub Marketplace Developer Agreement.

After publishing, the release page will display a Marketplace label.

Click on it to view the listed action in GitHub Marketplace.

Testing the Published Action

To verify the published action, create a workflow referencing it directly from GitHub Marketplace:

name: greet-action
on:
  workflow_dispatch:
jobs:
  greet:
    name: "Test: Greet Action"
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v3
      - name: Greet Action
        uses: r3d-shadow/custom-github-action@1.0.1
        with:
          name: "Safeer"
          message: "Testing the Released GitHub Action!"

Trigger the workflow from the Actions tab, select "Greet Action," and manually start it. Once it runs, review the logs to confirm the expected output message.

By following these steps, you can create and publish a custom GitHub Action, enhancing your workflow automation capabilities and contributing to the GitHub community.