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
   

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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!)
   

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3. BUT
   This talk is not about GitHub Actions from the consumer side
   

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4. BUT
   This talk is about GitHub Actions from the developer side
   

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5. What?!
   Consumer: Developer:
   

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6. Build an Action
   Source
   

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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
   

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8. Build an Action – Where?
   • Own repository or inside your project repository in
   .github/actions/[nameOfAction]/
   • Own repository is reuseable
   

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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
   

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10. Build a Docker Action
    Source
    

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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
    

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12. Build a JavaScript Action
    Source
    

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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
    

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14. The Action Metadata file
    Source
    

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15. The Action Metadata file
    • Describes the Action
    • inputs, outputs, runs (commands), ...
    

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16. The Action Metadata file - Input
    • The (maybe required) input for the Action to run
    

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17. The Action Metadata file - Input
    • The (maybe required) input for the Action to run
    

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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
    

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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
    

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20. Want an example?
    https://github.com/Blackjacx/backlog-notifier
    

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