bundle-size.yml

name: Bundle Size

permissions:
  contents: read

on:
  pull_request:
    paths:
      - 'packages/**'
      - 'package.json'
      - 'pnpm-lock.yaml'
      - '.tool-versions'
      - '.size-limit.json'
      - '.github/workflows/bundle-size.yml'
      - '.bundle-size-skip-branch'

jobs:
  check-skip:
    runs-on: ubuntu-22.04
    outputs:
      skip: ${{ steps.skip-check.outputs.skip }}
    steps:
      - name: Checkout PR branch
        uses: actions/checkout@v4

      - name: Check if branch should skip size check
        id: skip-check
        env:
          BRANCH: ${{ github.head_ref }}
        run: |
          SKIP_FILE=".bundle-size-skip-branch"
          SKIP_BRANCH=$(grep -v '^[[:space:]]*#' "$SKIP_FILE" 2>/dev/null | grep -v '^[[:space:]]*$' | tr -d '[:space:]' || echo "")
          if [ "$SKIP_BRANCH" = "$BRANCH" ]; then
            echo "skip=true" >> "$GITHUB_OUTPUT"
            echo "::notice::Branch '$BRANCH' is set to skip size check"
          else
            echo "skip=false" >> "$GITHUB_OUTPUT"
          fi

  check-bundle-size:
    needs: check-skip
    if: needs.check-skip.outputs.skip != 'true'
    runs-on: ubuntu-22.04
    permissions:
      contents: read
      pull-requests: write
    env:
      CI_JOB_NUMBER: 1
    steps:
      # 1. Read the PR's runtime before switching branches, then keep that Node
      #    version for both base and PR builds to avoid cross-version size skew.
      #    Also keep the PR's size-limit config because the base branch may not have it.
      - name: Checkout PR branch for runtime config
        uses: actions/checkout@v4
        with:
          ref: ${{ github.sha }}
          persist-credentials: false
          # The merge commit and its two parents are enough for the base-SHA
          # derivation below; no full-history checkout is needed.
          fetch-depth: 2

      - name: Determine base SHA from the PR merge commit
        id: base-sha
        env:
          MERGE_SHA: ${{ github.sha }}
          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
        run: |
          # For pull_request events github.sha is the ephemeral merge commit
          # (refs/pull/N/merge): the PR head merged into the base-branch tip. The
          # PR-head sizes are built from this merge commit, so the base sizes must be
          # built from its FIRST PARENT to share the exact same base-branch baseline.
          #
          # Using the live base tip (github.event.pull_request.base.sha) instead lets
          # the two builds drift apart whenever the PR branch is behind the base
          # branch: unrelated growth that landed on the base branch gets mis-attributed
          # to the PR, producing uniform false-positive size increases across every
          # tracked bundle (including OSS bundles the PR never touched).
          if [ "$MERGE_SHA" = "$HEAD_SHA" ]; then
            echo "::error::Bundle size check needs a mergeable PR: github.sha equals the PR head, so no merge commit exists (the branch likely conflicts with the base branch). Rebase / resolve conflicts and re-run."
            exit 1
          fi
          read -ra parents <<< "$(git rev-list --parents -n 1 "$MERGE_SHA")"
          # parents[0] = merge commit, [1] = first parent (base), [2] = second parent (head)
          if [ "${#parents[@]}" -eq 0 ]; then
            echo "::error::Could not read parents of github.sha ($MERGE_SHA); the commit is not reachable in this checkout. Ensure this job checks out with fetch-depth: 2 or deeper."
            exit 1
          fi
          if [ "${#parents[@]}" -ne 3 ]; then
            echo "::error::Expected github.sha ($MERGE_SHA) to be a 2-parent merge commit, found $(( ${#parents[@]} - 1 )) parent(s); cannot determine a matching base baseline. Ensure this job checks out with fetch-depth: 2 or deeper."
            exit 1
          fi
          base_sha="${parents[1]}"
          head_parent="${parents[2]}"
          if [ "$head_parent" != "$HEAD_SHA" ]; then
            echo "::error::Merge commit second parent ($head_parent) does not match the PR head ($HEAD_SHA); unexpected merge structure."
            exit 1
          fi
          echo "base-sha=$base_sha" >> "$GITHUB_OUTPUT"
          echo "Base baseline (merge commit first parent): $base_sha"
          echo "PR head        (merge commit second parent): $head_parent"

      - name: Read runtime versions
        id: tool-versions
        uses: ./.github/actions/read-tool-versions

      - name: Setup Node
        uses: actions/setup-node@v4
        with:
          node-version: ${{ steps.tool-versions.outputs.node-version }}

      - name: Setup pnpm
        uses: pnpm/action-setup@v4

      - name: Save size-limit config
        run: cp .size-limit.json /tmp/size-limit-config.json

      # 2. Get base branch sizes from the merge commit's first parent so the base
      #    and PR-head builds share the same base-branch baseline (see base-sha step).
      - name: Checkout base branch
        uses: actions/checkout@v4
        with:
          # Only the working tree at the base parent is needed (not its history), so
          # the default shallow fetch-depth is enough; checkout@v4 fetches this SHA
          # directly since it is reachable from the base branch.
          ref: ${{ steps.base-sha.outputs.base-sha }}
          persist-credentials: false

      - name: Copy size-limit config to base branch
        run: cp /tmp/size-limit-config.json .size-limit.json

      - name: Install base dependencies
        run: pnpm install --frozen-lockfile

      - name: Build base branch
        run: pnpm run build

      - name: Verify build artifacts
        run: |
          missing=0
          for pkg in react-on-rails react-on-rails-pro react-on-rails-pro-node-renderer; do
            if ! ls packages/$pkg/lib/*.js >/dev/null 2>&1; then
              echo "::error::Missing build artifacts in packages/$pkg/lib/"
              missing=1
            fi
          done
          if [ $missing -eq 1 ]; then
            exit 1
          fi
          echo "All build artifacts verified"

      - name: Measure base branch sizes
        run: |
          pnpm exec size-limit --json > /tmp/base-sizes.json
          echo "Base branch sizes:"
          cat /tmp/base-sizes.json

      # 3. Checkout PR and set dynamic limits
      - name: Checkout PR branch
        uses: actions/checkout@v4
        with:
          ref: ${{ github.sha }}
          persist-credentials: false

      - name: Install PR dependencies
        run: pnpm install --frozen-lockfile

      - name: Set dynamic limits (base + 0.5KB)
        run: node scripts/bundle-size.mjs set-limits --base /tmp/base-sizes.json

      - name: Copy .size-limit.json file with limits to tmp directory
        run: cp .size-limit.json /tmp/.size-limit-with-limits.json

      # 4. Run the action with dynamic limits
      - name: Check bundle size
        uses: andresz1/size-limit-action@v1
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}
          package_manager: pnpm
          build_script: build-for-size-limit
          skip_step: install