wasm-size.yml

name: WASM Size Budget

on:
  pull_request:
    branches: [main]

permissions:
  pull-requests: write   # needed to post the size-change comment
  contents: read

jobs:
  wasm-size:
    name: Build & check WASM sizes
    runs-on: ubuntu-latest

    steps:
      - name: Checkout PR branch
        uses: actions/checkout@v4
        with:
          fetch-depth: 0   # full history so we can checkout the base

      # ── Rust toolchain ────────────────────────────────────────────────────

      - name: Install Rust stable + wasm32 target
        uses: dtolnay/rust-toolchain@stable
        with:
          targets: wasm32-unknown-unknown

      - name: Cache Cargo registry
        uses: actions/cache@v4
        with:
          path: |
            ~/.cargo/registry
            ~/.cargo/git
            target
          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
          restore-keys: |
            ${{ runner.os }}-cargo-

      # ── Binaryen (wasm-opt) ───────────────────────────────────────────────

      - name: Install wasm-opt
        run: |
          sudo apt-get update -q
          sudo apt-get install -y binaryen

      # ── Build HEAD (PR branch) ────────────────────────────────────────────

      - name: Build contracts (PR)
        run: cargo build --target wasm32-unknown-unknown --release

      - name: Optimise WASM files (PR)
        run: |
          for f in target/wasm32-unknown-unknown/release/*.wasm; do
            wasm-opt -O3 -o "$f" "$f"
          done

      - name: Record PR sizes
        id: pr_sizes
        run: |
          mkdir -p /tmp/wasm-sizes
          for f in target/wasm32-unknown-unknown/release/*.wasm; do
            name=$(basename "$f" .wasm)
            size=$(wc -c < "$f")
            echo "$size" > "/tmp/wasm-sizes/pr_${name}"
          done

      # ── Build BASE (target branch) ────────────────────────────────────────

      - name: Checkout base branch
        run: git checkout "${{ github.base_ref }}"

      - name: Build contracts (base)
        run: cargo build --target wasm32-unknown-unknown --release

      - name: Optimise WASM files (base)
        run: |
          for f in target/wasm32-unknown-unknown/release/*.wasm; do
            wasm-opt -O3 -o "$f" "$f"
          done

      - name: Record base sizes
        run: |
          for f in target/wasm32-unknown-unknown/release/*.wasm; do
            name=$(basename "$f" .wasm)
            size=$(wc -c < "$f")
            echo "$size" > "/tmp/wasm-sizes/base_${name}"
          done

      # ── Compare and report ────────────────────────────────────────────────

      - name: Compare sizes and determine outcome
        id: compare
        run: |
          python3 - <<'PYEOF'
          import os, sys

          size_dir = "/tmp/wasm-sizes"
          files = set()

          # Keep in sync with TEST_CONTRACTS in scripts/gen_baseline.py: these
          # crates are test fixtures, not production contracts, and are exempt
          # from the size budget.
          TEST_CONTRACTS = {"test_faucet", "test_token"}

          for fname in os.listdir(size_dir):
              if fname.startswith("pr_"):
                  name = fname[3:]   # strip "pr_" prefix to get contract name
                  if name not in TEST_CONTRACTS:
                      files.add(name)

          WARN_THRESHOLD  = 0.05   # 5%
          BLOCK_THRESHOLD = 0.10   # 10%

          rows = []
          worst_ratio = 0.0
          block = False

          for contract in sorted(files):
              pr_file   = os.path.join(size_dir, f"pr_{contract}")
              base_file = os.path.join(size_dir, f"base_{contract}")

              pr_size = int(open(pr_file).read().strip())

              if os.path.exists(base_file):
                  base_size = int(open(base_file).read().strip())
                  delta     = pr_size - base_size
                  ratio     = delta / base_size if base_size else 0
                  pct       = ratio * 100

                  if ratio > BLOCK_THRESHOLD:
                      status = "🔴 BLOCK"
                      block  = True
                  elif ratio > WARN_THRESHOLD:
                      status = "🟡 WARN"
                  elif delta < 0:
                      status = "🟢"
                  else:
                      status = "✅"

                  rows.append(f"| `{contract}` | {base_size:,} | {pr_size:,} | {delta:+,} | {pct:+.1f}% | {status} |")
                  worst_ratio = max(worst_ratio, ratio)
              else:
                  rows.append(f"| `{contract}` | — | {pr_size:,} | +{pr_size:,} | new | 🆕 |")

          table = "\n".join(rows)

          comment = f"""## WASM Size Report

          | Contract | Base (bytes) | PR (bytes) | Delta | Change | Status |
          |---|---|---|---|---|---|
          {table}

          **Thresholds:** warn at +5%, block at +10% growth.
          """

          with open(os.environ["GITHUB_OUTPUT"], "a") as f:
              f.write(f"block={'true' if block else 'false'}\n")
              # Write multi-line output using a heredoc delimiter
              delimiter = "EOF_SIZE_REPORT"
              f.write(f"comment<<{delimiter}\n{comment}\n{delimiter}\n")

          sys.exit(1 if block else 0)
          PYEOF

      # ── Post comment ──────────────────────────────────────────────────────

      - name: Post size report as PR comment
        if: always()
        uses: marocchino/sticky-pull-request-comment@v2
        with:
          header: wasm-size-report
          message: ${{ steps.compare.outputs.comment }}

      # The compare step already exits 1 when block=true, so the job fails.
      # The sticky comment step runs regardless (if: always()) so reviewers
      # always see the table even when the build is blocked.