preview-url-comment.yml

# GitHub Action that creates a comment displaying the lit.dev preview URL for
# each PR, and updates the comment on each push.
name: Preview URL Comment

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  preview-url-comment:
    runs-on: ubuntu-latest
    timeout-minutes: 10

    steps:
      - name: Generate preview URL
        id: gen-url
        run: echo "::set-output name=url::https://pr${{ github.event.number }}-$(echo ${{ github.event.pull_request.head.sha }} | cut -c1-7)---lit-dev-5ftespv5na-uc.a.run.app/"

      # https://github.com/peter-evans/find-comment
      - name: Find existing comment
        uses: peter-evans/find-comment@v1
        id: find-comment
        with:
          issue-number: ${{ github.event.pull_request.number }}
          comment-author: github-actions[bot]
          body-includes: preview of this PR will be available

      # https://github.com/peter-evans/create-or-update-comment
      - name: Create comment (if new)
        if: ${{ steps.find-comment.outputs.comment-id == 0 }}
        uses: peter-evans/create-or-update-comment@v1
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          issue-number: ${{ github.event.pull_request.number }}
          edit-mode: replace
          body: |
            A live preview of this PR will be available at the URL(s) below.
            The latest URL will be appended to this comment on each push.
            Each build takes ~5-10 minutes, and will 404 until finished.

            ${{ steps.gen-url.outputs.url }}
          reactions: eyes

      - name: Update comment (if existing)
        if: ${{ steps.find-comment.outputs.comment-id != 0 }}
        uses: peter-evans/create-or-update-comment@v1
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          comment-id: ${{ steps.find-comment.outputs.comment-id }}
          edit-mode: append
          body: ${{ steps.gen-url.outputs.url }}