The easiest way to start taking advantage of CUE’s powerful validation is to use it to check existing configuration files. By adding this check to your development or deployment process you can catch and fix errors before they affect downstream systems.

This guide shows you how to use the cue command to validate a GitHub Actions workflow file using a curated module from the CUE Central Registry – all without writing any schemas or policies in CUE.

Choose a GitHub Actions workflow file

This example is adapted from GitHub’s actions/starter-workflows repository, but you should use any GitHub Actions workflow file that’s relevant to your situation.

# filepath: workflow.yml

name: Go
on:
  pull_request:
    branches: [ main ]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4
    - name: Set up Go
      uses: actions/setup-go@v4
      with:
        go-version: '1.20'
    - name: Build
      run: go build -v ./...
    - name: Test
      run: go test -v ./...

Validate the workflow file

$ cue vet -c -d '#Workflow' cue.dev/x/githubactions@latest workflow.yml

This command uses the #Workflow definition from the githubactions package to check the workflow.yml file. Because cue vet doesn’t display any errors, you know that the curated module has validated your configuration file.

If you see an error message mentioning “too many requests” then login to the Central Registry and re-run this command. The Central Registry allows more requests from authenticated users.

Validate more workflow files

GitHub repositories often contain multiple workflow files whose jobs get triggered by different events or perform different tasks. To check each workflow you could repeat the cue vet command for one or more files, like this:

$ cue vet -c -d '#Workflow' cue.dev/x/githubactions@latest .github/workflows/test.yml
$ cue vet -c -d '#Workflow' cue.dev/x/githubactions@latest .github/workflows/release.yml

However, an easy alternative is to set up a simple CUE file that embeds your workflow files and validates them all with a single command. Read more about this option in Validating multiple GitHub Actions workflow files …

Next steps

Validating your existing configuration files with CUE can help make development and deployments safer, but defining those same files in CUE lets you build on its first-class templating, referencing, and policy features. Take the first step with Getting started with GitHub Actions + CUE …