Lession learned - How to build a GitHub Action

Given at a company internal thundertalk.

Me and a few colleagues participated at the GitHub Actions Hackathon 2020.
We didn't know how to build a GitHub Action.
This slides gives you a roughly overview how you can build a GitHub Action by yourself.

Transcript

1. How to build a GitHub Action
2. About GitHub Actions (consumer side) • CI/CD • 4 runners • macOS, Windows, Linux and self hosted • Run on real machines • There is pre installed software • There are environment variables • There is also a ready-to-use GitHub Token • Full acces to the GitHub API via the Context (and more!)
3. BUT This talk is not about GitHub Actions from the consumer side
4. BUT This talk is about GitHub Actions from the developer side
5. What?! Consumer: Developer:
6. Build an Action Source
7. Build an Action • “Native” with JavaScript or Docker container • JS is • faster • runs on all runners • not that flexible than a Docker container • Docker is • slower • runs only on Linux runners (shouldn’t be a problem, right?) • 100 percent flexible
8. Build an Action – Where? • Own repository or inside your project repository in .github/actions/[nameOfAction]/ • Own repository is reuseable
9. Build an Action – Version! • commit -> author/repo-name@745bc508 • tag -> author/repo-name@v1.0 • branch -> author/repo-name@master • Actions in your project repository don’t require this of course
10. Build a Docker Action Source
11. Build a Docker Action • Createa a Dockerfile • Requires a ENTRYPOINT • Create a Action Metadata file • (More about this later) • Write the Actions code in the entrypoint
12. Build a JavaScript Action Source
13. Build a JavaScript Action • Create a Action Metadata file • (More about this later) • Install Action toolskits • npm install @actions/core • npm install @actions/github • Write the Action code in a file called index.js
14. The Action Metadata file Source
15. The Action Metadata file • Describes the Action • inputs, outputs, runs (commands), ...
16. The Action Metadata file - Input • The (maybe required) input for the Action to run
17. The Action Metadata file - Input • The (maybe required) input for the Action to run
18. The Action Metadata file - Output • The (maybe) output of the Action • An Action assembles an Android Project. The output is the apk/aab. • The output can be used with the expression syntax
19. The Action Metadata file - Run • Run describes how the Action should be run. Docker or JavaScript • Docker: JS: Dockerfile or any public Docker image
20. Want an example? https://github.com/Blackjacx/backlog-notifier