name: Generate check

on:
  push:
    paths:
      - '**/*_gen.go'
  pull_request:
    paths:
      - '**/*_gen.go'

jobs:
  check-generate:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v3

      - name: Save pre-generate git state
        run: git status --porcelain > pre-generate.txt

      - name: Run go generate
        run: go generate ./...

      - name: Save post-generate git state
        run: git status --porcelain > post-generate.txt

      - name: Check for changes
        run: |
          if ! diff pre-generate.txt post-generate.txt | grep .; then
            echo "No files changed by go generate"
          else
            echo "go generate produced changes; commit those first" >&2
            exit 1
          fi