GitHub Actions: Using If Conditions to Control Job Execution in a Workflow

Welcome back to our exploration of GitHub Actions! Today we’ll dive into a vital feature that offers more control and customization to your workflows – the use of if conditions to control job execution.

Understanding how to control the flow of jobs based on certain conditions is a fundamental part of creating intelligent, dynamic workflows.

If Conditional Jobs

In GitHub Actions, if conditionals can be used to determine if a step or job should run. This conditional generally comes after the if keyword and utilizes the context and expression syntax.

Expressions and Contexts

Expressions allow you to use a range of functions and operators to evaluate certain conditions, while contexts provide access to the specific objects within the GitHub Actions environment.

For instance, you can use expressions and contexts together to run a job only if the event triggering the workflow was a push event:

jobs:
  build:
    if: github.event_name == 'push'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2
      # ... additional steps ...

jobs:

build:

if: github.event_name == 'push'

runs-on: ubuntu-latest

steps:

- name: Checkout code

uses: actions/checkout@v2

# ... additional steps ...

In this example, github is a context that provides access to the event triggering the workflow, and github.event_name == 'push' is an expression that evaluates to true only when the event name is ‘push’.

Using If with Steps

if conditions can also be used with individual steps. Here is an example of a step that only runs when the workflow event is a pull request:

steps:
  - name: Say hello when a PR is submitted
    run: echo "Hello! A new PR has been submitted."
    if: github.event_name == 'pull_request'

steps:

- name: Say hello when a PR is submitted

run: echo "Hello! A new PR has been submitted."

if: github.event_name == 'pull_request'

Complex Conditions

You can also write more complex conditions using logical operators like && (and) and || (or). For instance, you might want to run a job only when the event is a push and the push is to the main branch:

jobs:
  build:
    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2
      # ... additional steps ...

jobs:

build:

if: github.event_name == 'push' && github.ref == 'refs/heads/main'

runs-on: ubuntu-latest

steps:

- name: Checkout code

uses: actions/checkout@v2

# ... additional steps ...

This job will only run if both conditions are true.

Conclusion

The if conditional in GitHub Actions provides a powerful way to control how and when your jobs and steps are executed. This gives you the flexibility to tailor your workflows to suit your specific needs, making them more efficient and intelligent.

Remember, the key to mastering if conditions is to understand expressions and contexts, and how to use them together to evaluate your desired conditions. Happy coding!