Why your GitHub action is not triggered by other actions

In this blog post I explain why GitHub actions don’t trigger each other by default, helping you how to achieve it.

Last week I wrote about how I configured a GitHub action to change this blog theme every day. Today I will explain you why I lost some time trying to understand why that action was not triggering my deploy to GitHub Pages action.

Before

Let's first do a side by side comparison on how each action is triggered:

name: publish

on:
  push:
    branches:
      - master

Deploy is based on commits made to master

name: update-theme-color

on:
  schedule:
    - cron: "0 0 * * *"

Change blog theme color is based on a cron job

Intuitively you would think that once the update-theme-color action runs, which creates a new commit in master, triggers the publish action, since it reacts to master branch updates.

However...

That is not the case! By default GitHub Actions don't trigger each other to prevent recursive runs. For an action X to be triggered by action Y, then action X needs to observe action Y execution.

How

To observe actions execution, the workflow_run reaction needs to be included. Here's how I reconfigured the publish action:

name: publish

on:
  push:
    branches:
      - master
  workflow_run:
    workflows: ["update-theme-color"]
    types: 
      - completed