iterate on github.event.commits in github action script

Question

I've written action in Github actions. In push events, a variable is provided by GitHub that starts with github.

Json preview of the variable is:

{
    "event_name": "push",
    "event": {
      "after": "aaaaaaaaaaaaaaaaa",
      "base_ref": null,
      "before": "bbbbbbbbbbbbbbbb",
      "commits": [
        {
          "author": {
            "username": "myUser"
          },
          "id": "bbbbbbbbbbbbbbbb",
          "message": "myCommitMessage",
          "url": "https://github.com/myUser/myRepo/commit/bbbbbbbbbbbbbbbb"
        }
      ],
      "compare": "https://github.com/myUser/myRepo/compare/" 
      }
  }

I want to write a script that iterates on github.event.commits and creates something like this:

commits=${{github.event.commits}}
length=${#commits[@]}
for (( i = 0; i < length; i++ )); do
  commit=${{github.event.commits[i]}}
  echo url=${{commit.url}}
  echo sha=${{commit.id}}
  echo actor=${{commit.author.username}}
  echo message=${{commit.message}}
done

But the id doesn't work. I got this error:

Unrecognized named-value: 'i'. Located at position 22 within expression: github.event.commits[i]

Answer 1

Does it have to be bash? You could use jq, but this might become a bit ugly if it gets more complex:

- run: echo '${{ toJSON(github.event.commits) }}' | jq ".[0].author"

Otherwise I can recommend the github-script action which should make your code much nicer:

- uses: actions/github-script@v6
  with:
    script: |
      const commits = ${{ toJSON(github.event.commits) }}
      for (const commit of commits) {
        console.log(commit);
      }