github: add sizeguard presubmit test (#9719)

- Add a presubmit check after the android build to check the
   built artifact sizes against previous build sizes.
 - If the size built is +20K over the previous, then the test
   fails.
 - This prevents dramatic size increases of our mobile build

.github/workflows/presubmit.yml

@@ -67,7 +67,16 @@ jobs:
         # Only build 1 64 bit target during presubmit to cut down build times during presubmit
         # Continuous builds will build everything
         run: |
-          cd build/android && printf "y" | ./build.sh presubmit arm64-v8a
+          pushd .
+          cd build/android && printf "y" | ./build.sh presubmit-with-archive arm64-v8a
+          popd
+      - name: Check artifact sizes
+        run: |
+          python3 test/sizeguard/dump_artifact_size.py out/*.aar > current_size.json
+          python3 test/sizeguard/check_size.py current_size.json \
+              --target-branch origin/main \
+              --threshold 20480 \
+              --artifacts filament-android-release.aar/jni/arm64-v8a/libfilament-jni.so
 
   build-ios:
     name: build-iOS

build/common/build-common.sh

@@ -39,6 +39,11 @@ if [[ "$TARGET" == "presubmit-with-test" ]]; then
     RUN_TESTS=-u
 fi
 
+if [[ "$TARGET" == "presubmit-with-archive" ]]; then
+    BUILD_RELEASE=release
+    GENERATE_ARCHIVES=-a
+fi
+
 if [[ "$TARGET" == "debug" ]]; then
     BUILD_DEBUG=debug
     GENERATE_ARCHIVES=-a

test/sizeguard/check_size.py

@@ -0,0 +1,190 @@
+# Copyright (C) 2026 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#!/usr/bin/env python3
+
+import argparse
+import json
+import os
+import sys
+import urllib.request
+import urllib.error
+import subprocess
+
+# The base URL where historical size data is stored
+BASE_URL = "https://raw.githubusercontent.com/google/filament-assets/main/sizeguard/"
+
+def get_merge_base(target_branch="origin/main"):
+  """Finds the merge base between HEAD and the target branch."""
+  try:
+    # Fetch the target branch to ensure we have the reference
+    result = subprocess.run(
+      ["git", "merge-base", "HEAD", target_branch],
+      stdout=subprocess.PIPE,
+      stderr=subprocess.PIPE,
+      check=True,
+      text=True
+    )
+    return result.stdout.strip()
+  except subprocess.CalledProcessError:
+    print(f"Warning: Could not determine merge base with {target_branch}.", file=sys.stderr)
+    return None
+
+def get_ancestors(start_commit, count=50):
+  """Returns a list of ancestor commit hashes."""
+  try:
+    result = subprocess.run(
+      ["git", "rev-list", f"--max-count={count}", start_commit],
+      stdout=subprocess.PIPE,
+      stderr=subprocess.PIPE,
+      check=True,
+      text=True
+    )
+    return result.stdout.strip().splitlines()
+  except subprocess.CalledProcessError as e:
+    print(f"Error listing ancestors: {e}", file=sys.stderr)
+    return []
+
+def fetch_json(commit_hash):
+  """Fetches the JSON file for the given commit from the assets repo."""
+  url = f"{BASE_URL}{commit_hash}.json"
+  try:
+    with urllib.request.urlopen(url) as response:
+      if response.status == 200:
+        print(f"Found historical data for commit {commit_hash}")
+        return json.loads(response.read().decode('utf-8'))
+  except urllib.error.HTTPError as e:
+    if e.code == 404:
+      return None
+    print(f"Warning: HTTP error fetching {url}: {e}", file=sys.stderr)
+  except Exception as e:
+    print(f"Warning: Error fetching {url}: {e}", file=sys.stderr)
+  return None
+
+def flatten_data(data):
+  """Flattens the JSON structure into a dictionary of name -> size."""
+  flat = {}
+  for item in data:
+    # Top level archive
+    flat[item['name']] = item['size']
+    # Inner content
+    if 'content' in item:
+      for inner in item['content']:
+        # Key format: ArchiveName/InnerName
+        key = f"{item['name']}/{inner['name']}"
+        flat[key] = inner['size']
+  return flat
+
+def main():
+  parser = argparse.ArgumentParser(
+    description="Compare current artifact sizes against historical data."
+  )
+  parser.add_argument(
+    "current_json", help="Path to the JSON file generated for the current build."
+  )
+  parser.add_argument(
+    "--threshold", type=int, default=20480, help="Size increase threshold in bytes (default: 20KB)."
+  )
+  parser.add_argument(
+    "--target-branch", default="origin/main", help="The branch to compare against."
+  )
+  parser.add_argument(
+    "--artifacts", nargs="+",
+    help="List of artifact paths to check (e.g. 'foo.aar' or 'foo.aar/lib/arm64/bar.so')."
+  )
+
+  args = parser.parse_args()
+
+  if not os.path.exists(args.current_json):
+    print(f"Error: Current JSON file not found: {args.current_json}", file=sys.stderr)
+    sys.exit(1)
+
+  with open(args.current_json, 'r') as f:
+    current_data = json.load(f)
+
+  # 1. Find the starting commit (merge base)
+  start_commit = get_merge_base(args.target_branch)
+  if not start_commit:
+    print("Error: Could not determine a valid starting commit to search.", file=sys.stderr)
+    sys.exit(1)
+
+  print(f"Merge base with {args.target_branch} is {start_commit}")
+
+  # 2. Search for historical data
+  ancestors = get_ancestors(start_commit)
+  base_data = None
+  base_commit = None
+
+  for commit in ancestors:
+    base_data = fetch_json(commit)
+    if base_data:
+      base_commit = commit
+      break
+
+  if not base_data:
+    print(f"Warning: No historical size data found in the last {len(ancestors)} ancestors.",
+          file=sys.stderr)
+    sys.exit(0)
+
+  print(f"Comparing against historical data from commit {base_commit}")
+
+  # 3. Compare
+  current_flat = flatten_data(current_data)
+  base_flat = flatten_data(base_data)
+
+  failures = []
+  checked_count = 0
+
+  print(f"{'Artifact':<60} | {'Current':<10} | {'Base':<10} | {'Delta':<10} | {'Status'}")
+  print("-" * 110)
+
+  keys_to_check = args.artifacts if args.artifacts else current_flat.keys()
+
+  for name in keys_to_check:
+    if name not in current_flat:
+      print(f"Warning: Artifact '{name}' not found in current build output.", file=sys.stderr)
+      continue
+
+    current_size = current_flat[name]
+    checked_count += 1
+
+    status = "OK"
+    base_str = "N/A"
+    diff_str = "N/A"
+
+    if name in base_flat:
+      base_size = base_flat[name]
+      base_str = str(base_size)
+      diff = current_size - base_size
+      diff_str = f"{diff:+}"
+
+      if diff > args.threshold:
+        failures.append(name)
+        status = "FAIL"
+    else:
+      status = "NEW"
+
+    print(f"{name:<60} | {current_size:<10} | {base_str:<10} | {diff_str:<10} | {status}")
+
+  print("-" * 110)
+
+  if failures:
+    print(f"FAILURE: {len(failures)} artifacts exceeded threshold of {args.threshold} bytes.")
+    sys.exit(1)
+  else:
+    print(f"SUCCESS: {checked_count} artifacts checked. All within acceptable threshold.")
+    sys.exit(0)
+
+if __name__ == "__main__":
+  main()