How to use array input for a custom GitHub Actions

Question

I'm working on a GitHub Action workflow that uses an array for input.

I used this solution to simulate an array:

      - uses: actions/my-custom-ci
        with:
          subdirectories: src/main/java src/test/java

But I want to use a solution like this:

      - uses: actions/my-custom-ci
        with:
          subdirectories: 
                - src/main/java 
                - src/test/java

Is it possible to use an array input for custom GitHub Actions? If yes, how can we use an array input for custom GitHub Actions?

Answer 1

At the time of writing this answer, GitHub Actions doesn't support array types as input for actions. It only supports string | number | boolean (schema: with ref: definitions/env). So your approach is a valid workaround for now.

Just note that GitHub runners have jq installed by default, and GitHub Actions offers methods like fromJSON, toJSON and join, which may help you create a cleaner solution in case you want to generate a dynamic input of your custom action.

You can check google-github-actions/get-secretmanager-secrets's implementation where they accept multiple inputs specified by line breaks, not as a yaml array:

    - id: 'secrets'
      uses: 'google-github-actions/get-secretmanager-secrets@v1'
      with:
        secrets: |-
          token:my-project/docker-registry-token
          anotherOne:my-project/a-secret
          anotherOneToo:my-project/another-secret

Definitely, this might not be what you want to achieve. And it might not be worth refactoring your action. But it's a workaround for now.