tools/format-cpp: enforce clang-format 13

This patch updates `tools/format-cpp` so that if the `FORMATTER`
environment variable is not empty, the script tries to format with
`$FORMATTER`; otherwise, it tries `clang-format-13 -i` or, if not
available, `clang-format -i`.

In all cases, the script checks the major version of the selected
formatter with `--version`, failing before formatting if it's not 13.

Using exactly clang-format 13 is important for formatting consistency
across developers and CI systems because it's possible that a future
version of clang-format, given the same configuration file, formats
files dissimilarly.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: Ic81d8d09c35657b602de044f6123e8b11fc37c44
Reviewed-on: https://review.lttng.org/c/babeltrace/+/7151

diff --git a/tools/format-cpp b/tools/format-cpp
index 48703c29bbd643fb55dedd0589ee4c1c33bcc8f5..370baef9553dabf2aefce9d08e5bd89cc56d4d87 100755 (executable)
--- a/tools/format-cpp
+++ b/tools/format-cpp
@@ -2,11 +2,56 @@
 #
 # SPDX-License-Identifier: GPL-2.0-only
 #
-# Copyright (C) 2020 Philippe Proulx <pproulx@efficios.com>
-
-FORMATTER="${FORMATTER:-clang-format -i}"
-root_dir="$(dirname "${BASH_SOURCE[0]}")/.."
-find "$root_dir" \( -name '*.cpp' -o -name '*.hpp' \) \
-       ! -wholename '*/cpp-common/optional.hpp' \
-       ! -wholename '*/cpp-common/string_view.hpp' \
-       -exec $FORMATTER '{}' ';'
+# Copyright (C) 2020-2022 Philippe Proulx <pproulx@efficios.com>
+
+expected_formatter_major_version=13
+
+# Runs the formatter, making sure it's the expected version.
+format_cpp() {
+       local formatter=$1
+       local version
+
+       version=$($formatter --version)
+
+        # shellcheck disable=SC2181
+       if (($? != 0)); then
+               echo "Cannot execute \`$formatter --version\`." >&2
+               return 1
+       fi
+
+       if [[ "$version" != *"clang-format version $expected_formatter_major_version"* ]]; then
+               echo "Expecting clang-format $expected_formatter_major_version." >&2
+               echo >&2
+               echo Got: >&2
+               echo >&2
+               echo "$version" >&2
+               return 1
+       fi
+
+       local root_dir
+
+       root_dir="$(dirname "${BASH_SOURCE[0]}")/.."
+
+       # Using xargs to fail as soon as the formatter fails (`-exec`
+       # won't stop if its subprocess fails).
+       #
+       # shellcheck disable=SC2086
+       find "$root_dir" \( -name '*.cpp' -o -name '*.hpp' \) \
+               ! -wholename '*/cpp-common/optional.hpp' \
+               ! -wholename '*/cpp-common/string_view.hpp' \
+               -print0 | xargs -n1 -0 $formatter
+}
+
+if [[ -n "$FORMATTER" ]]; then
+       # Try using environment-provided formatter
+       formatter=$FORMATTER
+elif command -v clang-format-$expected_formatter_major_version &> /dev/null; then
+       # Try using the expected version of clang-format
+       formatter="clang-format-$expected_formatter_major_version -i"
+else
+       # Try using `clang-format` as is
+       formatter='clang-format -i'
+fi
+
+# Try to format files
+format_cpp "$formatter"