From 4bc083cc07d23bce51163f89759313f29d761e6e Mon Sep 17 00:00:00 2001
From: Yiqing Wang <yiqing@wangemail.com>
Date: Sun, 19 Jul 2026 23:23:21 -0700
Subject: [PATCH] dev-infra: make clang-format hermetic

---
 hack/clang-format.sh     | 77 ++++++++++++++++++++++++++++++++++++++++
 hack/update/proto-fmt.sh |  8 +----
 2 files changed, 78 insertions(+), 7 deletions(-)
 create mode 100755 hack/clang-format.sh

diff --git a/hack/clang-format.sh b/hack/clang-format.sh
new file mode 100755
index 000000000..7d6f84541
--- /dev/null
+++ b/hack/clang-format.sh
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+
+# Copyright 2026 Google LLC
+#
+# 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.
+
+set -o errexit -o nounset -o pipefail
+
+CLANG_FORMAT_VERSION="22.1.8"
+
+ROOT="$(git rev-parse --show-toplevel)"
+INSTALL_DIR="${ROOT}/bin/clang-format-install/${CLANG_FORMAT_VERSION}"
+CLANG_FORMAT_BIN="${INSTALL_DIR}/clang-format"
+
+if [[ ! -x "${CLANG_FORMAT_BIN}" ]]; then
+  os_name="$(uname -s)"
+  arch_name="$(uname -m)"
+
+  case "${os_name}/${arch_name}" in
+    Darwin/arm64)
+      wheel_url="https://files.pythonhosted.org/packages/2e/55/539cc1036dae16659f50500ca34838cc5b16cd3e98e3faaf164186b98093/clang_format-${CLANG_FORMAT_VERSION}-py2.py3-none-macosx_11_0_arm64.whl"
+      expected_sha="d1147107222c0dda3e4869e9e8c4a79f9ed1de83819e5274de42b82adf3d2129"
+      ;;
+    Darwin/x86_64)
+      wheel_url="https://files.pythonhosted.org/packages/5d/d8/29b9db6098da1a011ca3f7560c3942fa81404dbbb4367c3bd1d5c435da3b/clang_format-${CLANG_FORMAT_VERSION}-py2.py3-none-macosx_10_9_x86_64.whl"
+      expected_sha="fc2ac5bd0ea41af49968fb69426207806d5f7016cb8f4bfbd44f4f1ffe8d53f2"
+      ;;
+    Linux/aarch64|Linux/arm64)
+      wheel_url="https://files.pythonhosted.org/packages/50/25/a9734da014eecc1f54c051ad643a28f2f6643dcc812ac59320e80e2b1a3b/clang_format-${CLANG_FORMAT_VERSION}-py2.py3-none-manylinux_2_26_aarch64.manylinux_2_28_aarch64.whl"
+      expected_sha="48c3b8dcfe9d4e964ced0e744e0f1f8ddc711bce92e50f6cab21e10f54857d08"
+      ;;
+    Linux/x86_64)
+      wheel_url="https://files.pythonhosted.org/packages/e5/88/b82c066fa807da4ca2518fecf79071361f6324b77375e5e92c059c0697fd/clang_format-${CLANG_FORMAT_VERSION}-py2.py3-none-manylinux_2_27_x86_64.manylinux_2_28_x86_64.whl"
+      expected_sha="b00cff6bfd1f1686f073a4fdf1cb937dbd58bf7510c659477805c03afdea0816"
+      ;;
+    *)
+      echo "Unsupported platform ${os_name}/${arch_name}" >&2
+      exit 1
+      ;;
+  esac
+
+  echo "Downloading clang-format v${CLANG_FORMAT_VERSION} for ${os_name}/${arch_name}..." >&2
+  mkdir -p "${INSTALL_DIR}"
+  wheel="$(mktemp "${INSTALL_DIR}/clang-format.whl.XXXXXX")"
+  binary="$(mktemp "${INSTALL_DIR}/clang-format.XXXXXX")"
+  trap 'rm -f "${wheel}" "${binary}"' EXIT
+
+  # The PyPI wheels contain a standalone clang-format binary; Python is not
+  # needed to install or run it.
+  curl --proto '=https' --tlsv1.2 --fail --location --silent --show-error \
+    "${wheel_url}" --output "${wheel}"
+  actual_sha="$(shasum -a 256 "${wheel}" | awk '{print $1}')"
+  if [[ "${actual_sha}" != "${expected_sha}" ]]; then
+    echo "Checksum verification failed for clang-format download" >&2
+    echo "Expected: ${expected_sha}" >&2
+    echo "Got:      ${actual_sha}" >&2
+    exit 1
+  fi
+
+  unzip -p "${wheel}" clang_format/data/bin/clang-format >"${binary}"
+  chmod 0755 "${binary}"
+  mv "${binary}" "${CLANG_FORMAT_BIN}"
+  rm -f "${wheel}"
+  trap - EXIT
+fi
+
+exec "${CLANG_FORMAT_BIN}" "$@"
diff --git a/hack/update/proto-fmt.sh b/hack/update/proto-fmt.sh
index 493c71d97..06776cef0 100755
--- a/hack/update/proto-fmt.sh
+++ b/hack/update/proto-fmt.sh
@@ -19,13 +19,7 @@ set -o errexit -o nounset -o pipefail
 ROOT="$(git rev-parse --show-toplevel)"
 cd "${ROOT}"
 
-# Find clang-format in the PATH, and exit if not found.
-tool="clang-format"
-clangfmt="$(which "$tool" 2>/dev/null || true)"
-if [[ ! -x "${clangfmt}" ]]; then
-  echo "Failed to find ${tool}: please make sure it is in your PATH" >&2
-  exit 1
-fi
+clangfmt="${ROOT}/hack/clang-format.sh"
 
 # Find all top-level directories containing proto files, and run clangfmt on them.
 # shellcheck disable=SC2207 # reading array