Conditional Workflows in GitHub Actions

1. Introduction

Conditional workflows in GitHub Actions allow you to define when a job or step should run based on certain conditions. This enables more complex workflows that can react dynamically based on the state of your repository or the outcomes of previous jobs.

2. Key Concepts

• **Jobs**: Individual units of work that can run in parallel or sequentially.
• **Steps**: Individual tasks that are run as part of a job.
• **Conditions**: Statements that dictate when a job or step should execute.
• **Contexts**: Objects that contain information about the workflow run, which can be used for conditional logic.

3. Conditional Expressions

You can use conditional expressions to control the execution of jobs and steps. These expressions evaluate to either true or false. Common contexts used in expressions include:

• github: Information about the repository and the event that triggered the workflow.
• env: Environment variables defined in the workflow.
• jobs: The status of other jobs in the workflow.

4. Step-by-Step Example

Below is a workflow example where a job named "build" runs only if the job "test" was successful:

name: CI

on:
  push:
    branches:
      - main

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2
      
      - name: Run tests
        run: npm test

  build:
    runs-on: ubuntu-latest
    needs: test
    if: success()  # This job runs only if "test" is successful
    steps:
      - name: Build project
        run: npm run build
        

5. Best Practices

• Use clear and descriptive names for jobs and steps to improve readability.
• Limit the use of complex conditional expressions to maintain clarity.
• Document your workflows with comments to explain the logic behind conditional statements.
• Test your workflows thoroughly to ensure that conditions trigger as expected.

6. FAQ