Conditionally running a second job in a GitHub Actions workflow

My simonwillisonblog-backup workflow periodically creates a JSON backup of my blog's PostgreSQL database, using db-to-sqlite and sqlite-diffable. It then commits any changes back to the repo using this pattern:

    - name: Commit any changes
      run: |-
        git config user.name "Automated"
        git config user.email "actions@users.noreply.github.com"
        git add simonwillisonblog
        timestamp=$(date -u)
        git commit -m "Latest data: ${timestamp}" || exit 0
        git push

I decided to upgrade it to also build and deploy a SQLite database of the content to datasette.simonwillison.net - but only if a change had been detected.

I figured out the following pattern for doing that.

First, I added a line to the above block that set a change_detected output variable for that step if it made it past the || exit 0. I also added an id to the step so I could reference it later on:

    - name: Commit any changes
      id: commit_and_push
      run: |-
        git config user.name "Automated"
        git config user.email "actions@users.noreply.github.com"
        git add simonwillisonblog
        timestamp=$(date -u)
        git commit -m "Latest data: ${timestamp}" || exit 0
        git push
        echo "::set-output name=change_detected::1"

This next piece took me a while to figure out: I also had to declare that output variable at the top of the initial job, copying the result of the named step:

jobs:
  backup:
    runs-on: ubuntu-latest
    outputs:
      change_detected: ${{ steps.commit_and_push.outputs.change_detected }}

Without this, the output is not visible to the second job.

My second job started like this:

  build_and_deploy:
    runs-on: ubuntu-latest
    needs: backup
    if: ${{ inputs.force_deploy || needs.backup.outputs.change_detected }}
    steps:

This second job is called build_and_deploy and specify that it needs: backup - so it should run directly after that backup job completes.

That new job has an if: expression which looks at needs.backup.outputs.change_detected to read the variable that was set by my echo "::set-output line.

I'm also checking inputs.force_deploy here. That's a separate mechanism, which allows me to trigger the workflow with manually and specify that a deploy should happen even if no changes were detected - useful for when I alter the code that configures the deployed Datasette instance.

The force_deploy variable comes from this section at the start of the YAML:

on:
  push:
    branches:
      - main
  workflow_dispatch:
    inputs:
      force_deploy:
        description: 'Deploy even if no changes detected'
        required: false 
        type: boolean

This configuration adds the following UI which I can use to manually trigger the workflow:

Created 2022-07-11T13:39:01-07:00, updated 2022-07-11T17:05:01-07:00 · History · Edit

Conditionally running a second job in a GitHub Actions workflow

Related