---

name: action-builder description: Create custom GitHub Actions (composite, Docker, or JavaScript). Use when building reusable actions, creating custom workflow steps, or packaging logic for distribution. Trigger words include "create action", "custom action", "build action", "composite action", "Docker action".

Action Builder

Build custom GitHub Actions for reusable workflow logic.

Quick Start

Choose action type based on requirements:

• Composite: Combine multiple workflow steps (simplest, no code)
• Docker: Run containerized logic (any language, slower startup)
• JavaScript: Fast execution, Node.js required

Instructions

Step 1: Choose Action Type

Use Composite when:

• Combining existing actions and shell commands
• No custom code needed
• Fast execution required
• Example: Setup environment with multiple tools

Use Docker when:

• Need specific runtime environment
• Using non-JavaScript languages
• Complex dependencies
• Example: Custom linting tool, data processing

Use JavaScript when:

• Need programmatic control
• Fast startup time critical
• Interacting with GitHub API
• Example: Issue labeler, PR validator

Step 2: Create Action Structure

All action types need:

Copyaction-name/
├── action.yml          # Action metadata
├── README.md           # Documentation
└── [implementation]    # Type-specific files

Step 3: Define action.yml

Required fields:

Copyname: 'Action Name'
description: 'What the action does'
author: 'Your Name'

inputs:
  input-name:
    description: 'Input description'
    required: true
    default: 'default-value'

outputs:
  output-name:
    description: 'Output description'
    value: ${{ steps.step-id.outputs.output-name }}

runs:
  using: 'composite|docker|node16'
  # Type-specific configuration

Step 4: Implement Action Logic

For Composite Actions:

Copyruns:
  using: 'composite'
  steps:
    - name: Step name
      run: echo "Command"
      shell: bash
    - uses: actions/checkout@v3

For Docker Actions:

Copyruns:
  using: 'docker'
  image: 'Dockerfile'
  args:
    - ${{ inputs.input-name }}

For JavaScript Actions:

Copyruns:
  using: 'node16'
  main: 'dist/index.js'

Step 5: Test Action Locally

Test in workflow:

Copyjobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - uses: ./  # Test local action
        with:
          input-name: 'test-value'

Step 6: Version and Publish

Versioning:

• Use semantic versioning (v1.0.0)
• Create Git tags for releases
• Maintain major version tags (v1, v2)

Publishing:

• Push to GitHub repository
• Create release with tag
• Add to GitHub Marketplace (optional)

Common Patterns

Input Validation

Copyinputs:
  environment:
    description: 'Deployment environment'
    required: true
  region:
    description: 'AWS region'
    required: false
    default: 'us-east-1'

Output Setting

Composite:

Copyecho "output-name=value" >> $GITHUB_OUTPUT

JavaScript:

Copycore.setOutput('output-name', 'value');

Error Handling

Composite:

Copyif [ $? -ne 0 ]; then
  echo "::error::Operation failed"
  exit 1
fi

JavaScript:

Copytry {
  // Action logic
} catch (error) {
  core.setFailed(error.message);
}

Advanced

For detailed implementation guides:

• Composite Actions - Multi-step workflows
• Docker Actions - Containerized actions
• Inputs and Outputs - Data handling patterns

Troubleshooting

Action not found:

• Verify action.yml exists in repository root
• Check action path in workflow (uses: owner/repo@version)

Inputs not working:

• Confirm input names match action.yml
• Check required vs. optional inputs
• Verify default values

Outputs not available:

• Ensure output is set before job completes
• Check step ID matches output reference
• Verify output syntax (${{ steps.id.outputs.name }})