How I Published My First GitHub Action!

Medium: How I Published My First GitHub Action!

As I explored writing open-source software, I decided to try building a small GitHub Action. This blog post outlines my journey from the initial struggles to successfully publishing the Action on GitHub Marketplace. I hope this will be helpful for anyone looking to do the same!

Setting the Stage

At first, I focused solely on writing the code to make the Action work. However, publishing it to the GitHub Marketplace required more than just functional code. Here's what I needed to prepare:

Workflow Configuration: Create a .github/workflows file to define how the Action will run.
Dependency Management: For example, if your code is written in JavaScript and uses external packages, you'll need a package.json file.
Action Description: Write an action.yaml file to provide detailed information about the Action.

After testing and fixing bugs, my GitHub Action was finally functional. I then created a release.

At this point, I noticed an alert on my repository:

I thought I was done. But when I tried to use the Action in another repository like this:

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jobs:
  review:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write

    steps:
     - name: Review the code with Gemini
       uses: bunheree/gemini-review@v1.0.0
    ...

The Problem

When the GitHub Action ran, it failed with the following error:

ERR_MODULE_NOT_FOUND(packageName, fileURLToPath(base), null)
^
Error [ERR_MODULE_NOT_FOUND]: Cannot find package '@actions/core'

After researching, I discovered this error occurs because the @actions/core package is missing from /node_modules. This is a common issue when publishing GitHub Actions.

This usually happens when your source code hasn't been bundled.

Resolving the Issue

Step 1: Bundle the Action

To fix this, I used a bundler like esbuild or ncc to create a single JavaScript file that includes all dependencies. I chose @vercel/ncc.

Install @vercel/ncc globally:

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npm install -g @vercel/ncc

Then, build the source code:

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ncc build index.js --out dist

This generates a bundled version of your Action in a new folder:

Step 2: Update action.yaml

Initially, I had set the main entry point in action.yaml as index.js. After bundling the source code, I updated the file to point to dist/index.js instead:

runs:
  using: "node20"
  main: "dist/index.js"

Notes

Once all configurations are complete, don't forget to release a new version of your GitHub Action. You can then use it in other repositories like this:

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uses: bunheree/gemini-review@v1.0.2

Summary

Here’s a checklist for publishing a GitHub Action:

Set up the GitHub workflow action file.
Include configuration files (e.g., package.json) for your chosen language/environment.
Write the action.yaml file.
Bundle the Action using tools like esbuild or ncc.

You can check out the GitHub Action I created here: Review Pull Request Auto.

Conclusion

Publishing a GitHub Action may seem challenging at first, but it’s a rewarding experience. If you're planning to release one, I hope this guide helps you get started.

Happy coding!!! 👩🏼‍💻

I am always looking for feedback on my writing, so please let me know what you think. ❤️