test adding clang-format to CI

.github/workflows/build.yml

@@ -31,6 +31,8 @@ jobs:
       fail-fast: false
     steps:
     - uses: actions/checkout@v6
+    - name: Check clang-format
+      run: scripts/clang-format.sh ci
     - name: cmake
       run: CXX=${{ matrix.cxx }} cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release -DFLATBUFFERS_STRICT_MODE=ON -DFLATBUFFERS_STATIC_FLATC=ON .
     - name: build

scripts/clang-format.sh

@@ -0,0 +1,123 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# clang-format runner mirroring the CMake targets:
+# - diff: show formatting diff against empty tree
+# - ci: fail if any formatting changes would be applied
+# - fix: apply formatting changes against empty tree
+
+# Constants
+GIT_EMPTY_TREE_HASH=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+
+# Resolve paths
+SCRIPT_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+REPO_ROOT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null || echo "$SCRIPT_DIR/..")
+GIT_CLANG_FORMAT="$SCRIPT_DIR/git-clang-format.py"
+
+# Detect Python
+PYTHON_BIN=${PYTHON:-}
+if [[ -z "${PYTHON_BIN}" ]]; then
+	if command -v python3 >/dev/null 2>&1; then
+		PYTHON_BIN=python3
+	elif command -v python >/dev/null 2>&1; then
+		PYTHON_BIN=python
+	else
+		echo "Error: Python not found (set PYTHON env var or install python3)." >&2
+		exit 1
+	fi
+fi
+
+# Detect clang-format (can be overridden via --binary or CLANG_FORMAT_PROGRAM)
+CLANG_FORMAT_BIN=${CLANG_FORMAT_PROGRAM:-}
+if [[ -z "${CLANG_FORMAT_BIN}" ]]; then
+	if command -v clang-format >/dev/null 2>&1; then
+		CLANG_FORMAT_BIN=$(command -v clang-format)
+	else
+		CLANG_FORMAT_BIN=""
+	fi
+fi
+
+print_usage() {
+	cat <<EOF
+Usage: $(basename "$0") [--binary /path/to/clang-format] <diff|ci|fix>
+
+Subcommands:
+	diff   Show formatting diff vs empty tree (read-only)
+	ci     CI mode: exit non-zero if changes would be made
+	fix    Apply formatting changes vs empty tree
+
+Options:
+	--binary PATH   Path to clang-format binary (default: detect from PATH or CLANG_FORMAT_PROGRAM)
+
+Environment:
+	PYTHON                Python interpreter to use (default: detect python3/python)
+	CLANG_FORMAT_PROGRAM  clang-format binary path (alternative to --binary)
+EOF
+}
+
+# Parse args
+ARGS=()
+SUBCMD=""
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		--binary)
+			shift
+			CLANG_FORMAT_BIN=${1:-}
+			if [[ -z "${CLANG_FORMAT_BIN}" ]]; then
+				echo "Error: --binary requires a path." >&2
+				exit 2
+			fi
+			;;
+		diff|ci|fix)
+			SUBCMD="$1"
+			;;
+		-h|--help)
+			print_usage
+			exit 0
+			;;
+		*)
+			echo "Unknown argument: $1" >&2
+			print_usage
+			exit 2
+			;;
+	esac
+	shift
+done
+
+if [[ ! -f "$GIT_CLANG_FORMAT" ]]; then
+	echo "Error: git-clang-format.py not found at $GIT_CLANG_FORMAT" >&2
+	exit 1
+fi
+
+if [[ -z "$SUBCMD" ]]; then
+	echo "Error: missing subcommand (diff|ci|fix)." >&2
+	print_usage
+	exit 2
+fi
+
+# Build common command
+CMD=("$PYTHON_BIN" "$GIT_CLANG_FORMAT")
+if [[ -n "$CLANG_FORMAT_BIN" ]]; then
+	CMD+=("--binary=$CLANG_FORMAT_BIN")
+fi
+
+pushd "$REPO_ROOT" >/dev/null
+
+case "$SUBCMD" in
+	diff)
+		# Equivalent to: ${CLANG_FORMAT_COMMAND} --diff ${GIT_EMPTY_TREE_HASH}
+		"${CMD[@]}" --diff "$GIT_EMPTY_TREE_HASH"
+		;;
+	ci)
+		# Equivalent to: ${CLANG_FORMAT_COMMAND} --ci ${GIT_EMPTY_TREE_HASH}
+		"${CMD[@]}" --ci "$GIT_EMPTY_TREE_HASH"
+		;;
+	fix)
+		# Equivalent to: ${CLANG_FORMAT_COMMAND} ${GIT_EMPTY_TREE_HASH} -f
+		"${CMD[@]}" "$GIT_EMPTY_TREE_HASH" -f
+		;;
+esac
+
+popd >/dev/null
+