changed-packages.yaml

name: 'Determine changed packages'

on:
  workflow_call:
    outputs:
      package_changed:
        description: 'Dry run of turbo to determine which packages have changed since the last release'
        value: ${{ jobs.dry-run.outputs.package_changed }}

jobs:
  dry-run:
    runs-on: ubuntu-latest
    env:
      # The turbo filter here varies depending on if we're using this workflow in a PR or on a push to a branch
      # For PRs, we want to use `github.event.pull_request.base.sha` to tell turbo to see which packages changed since that SHA
      # For a branch push/merges, the above sha isn't available, so instead, we reference `github.event.before` to determine the previous `HEAD` of the branch we just pushed onto
      #   See SO answer for more info https://stackoverflow.com/a/61861763/2379922
      TURBO_REF_FILTER: ${{ github.event_name == 'pull_request' && github.event.pull_request.base.sha || 'HEAD^' }}
    outputs:
      # Defining a job output for used by the next jobs:
      # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idoutputs
      package_changed: ${{ steps.changeset.outputs.result }}

    steps:
      - uses: actions/checkout@v2
        with:
          # see `fetch-depth` in README: https://github.com/actions/checkout#checkout-v3,
          # we set to `0` so the referenced commits are available for the command below
          fetch-depth: 0

      - name: Changeset
        id: changeset
        shell: bash
        # 1. We need the 'output' of a turbo dry-run to get a json with all affected packages of these run.
        # 2. The multi line json string is wrapped in EOF delimeters to make the GHA happy: https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#multiline-strings
        # 3. We specify the .github/ folder as a dependency here. Just to be safe, if workflows changed, we use that to mean everything has changes pending... to force redeploys
        run: |
          echo 'result<<CHANGESET_DELIMITER' >> $GITHUB_OUTPUT
          echo "$(npx -y turbo build --dry-run=json --filter=...[$TURBO_REF_FILTER])" >> $GITHUB_OUTPUT
          echo 'CHANGESET_DELIMITER' >> $GITHUB_OUTPUT
      - name: Echo info
        shell: bash
        run: |
          echo "Changeset: ${{ steps.changeset.outputs.result }}"