Sanitize GitHub context in GitHub actions

Question

I'm trying to write a slack notification bot to trigger off of GitHub pull requests, but I'm running into a sanitization issue

I have an action defined as follows

  name: slack-notification
  on:
    pull_request:
      types: [closed]

  jobs:
    slack-notifications:
      runs-on: ubuntu-latest
      steps:
      - name: Send message to slack
        id: slack
        uses: slackapi/slack-github-action@v1.18.0
        with:
          payload: |
            {
              "blocks": [
                {
                  "type": "section",
                  "text": {
                    "type": "mrkdwn",
                    "text": "${{ github.event.pull_request.title }}"
                  }
                }
              ]
            }

This works great when the pull_request title is normal. However, if it includes rich text formatting, or anything that would break the JSON (think quotes, etc), the process fails. How do I sanitize to avoid this?

Answer 1

Try using toJSON to do the quoting

payload: |
  {
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": ${{ toJSON(github.event.pull_request.title) }}
        }
      }
    ]
  }