Add formatting check workflow

Bundle clang-format-diff with workflow

.github/workflows/clang-format-diff.py

@@ -0,0 +1,197 @@
+#!/usr/bin/env python3
+#
+# ===- clang-format-diff.py - ClangFormat Diff Reformatter ----*- python -*--===#
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===------------------------------------------------------------------------===#
+
+"""
+This script reads input from a unified diff and reformats all the changed
+lines. This is useful to reformat all the lines touched by a specific patch.
+Example usage for git/svn users:
+
+  git diff -U0 --no-color --relative HEAD^ | {clang_format_diff} -p1 -i
+  svn diff --diff-cmd=diff -x-U0 | {clang_format_diff} -i
+
+It should be noted that the filename contained in the diff is used unmodified
+to determine the source file to update. Users calling this script directly
+should be careful to ensure that the path in the diff is correct relative to the
+current working directory.
+"""
+from __future__ import absolute_import, division, print_function
+
+import argparse
+import difflib
+import re
+import subprocess
+import sys
+
+if sys.version_info.major >= 3:
+    from io import StringIO
+else:
+    from io import BytesIO as StringIO
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description=__doc__.format(clang_format_diff="%(prog)s"),
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+    parser.add_argument(
+        "-i",
+        action="store_true",
+        default=False,
+        help="apply edits to files instead of displaying a diff",
+    )
+    parser.add_argument(
+        "-p",
+        metavar="NUM",
+        default=0,
+        help="strip the smallest prefix containing P slashes",
+    )
+    parser.add_argument(
+        "-regex",
+        metavar="PATTERN",
+        default=None,
+        help="custom pattern selecting file paths to reformat "
+        "(case sensitive, overrides -iregex)",
+    )
+    parser.add_argument(
+        "-iregex",
+        metavar="PATTERN",
+        default=r".*\.(?:cpp|cc|c\+\+|cxx|cppm|ccm|cxxm|c\+\+m|c|cl|h|hh|hpp"
+        r"|hxx|m|mm|inc|js|ts|proto|protodevel|java|cs|json|s?vh?)",
+        help="custom pattern selecting file paths to reformat "
+        "(case insensitive, overridden by -regex)",
+    )
+    parser.add_argument(
+        "-sort-includes",
+        action="store_true",
+        default=False,
+        help="let clang-format sort include blocks",
+    )
+    parser.add_argument(
+        "-v",
+        "--verbose",
+        action="store_true",
+        help="be more verbose, ineffective without -i",
+    )
+    parser.add_argument(
+        "-style",
+        help="formatting style to apply (LLVM, GNU, Google, Chromium, "
+        "Microsoft, Mozilla, WebKit)",
+    )
+    parser.add_argument(
+        "-fallback-style",
+        help="The name of the predefined style used as a"
+        "fallback in case clang-format is invoked with"
+        "-style=file, but can not find the .clang-format"
+        "file to use.",
+    )
+    parser.add_argument(
+        "-binary",
+        default="clang-format",
+        help="location of binary to use for clang-format",
+    )
+    args = parser.parse_args()
+
+    # Extract changed lines for each file.
+    filename = None
+    lines_by_file = {}
+    for line in sys.stdin:
+        match = re.search(r"^\+\+\+\ (.*?/){%s}(\S*)" % args.p, line)
+        if match:
+            filename = match.group(2)
+        if filename is None:
+            continue
+
+        if args.regex is not None:
+            if not re.match("^%s$" % args.regex, filename):
+                continue
+        else:
+            if not re.match("^%s$" % args.iregex, filename, re.IGNORECASE):
+                continue
+
+        match = re.search(r"^@@.*\+(\d+)(?:,(\d+))?", line)
+        if match:
+            start_line = int(match.group(1))
+            line_count = 1
+            if match.group(2):
+                line_count = int(match.group(2))
+                # The input is something like
+                #
+                # @@ -1, +0,0 @@
+                #
+                # which means no lines were added.
+                if line_count == 0:
+                    continue
+            # Also format lines range if line_count is 0 in case of deleting
+            # surrounding statements.
+            end_line = start_line
+            if line_count != 0:
+                end_line += line_count - 1
+            lines_by_file.setdefault(filename, []).extend(
+                ["--lines", str(start_line) + ":" + str(end_line)]
+            )
+
+    # Reformat files containing changes in place.
+    has_diff = False
+    for filename, lines in lines_by_file.items():
+        if args.i and args.verbose:
+            print("Formatting {}".format(filename))
+        command = [args.binary, filename]
+        if args.i:
+            command.append("-i")
+        if args.sort_includes:
+            command.append("--sort-includes")
+        command.extend(lines)
+        if args.style:
+            command.extend(["--style", args.style])
+        if args.fallback_style:
+            command.extend(["--fallback-style", args.fallback_style])
+
+        try:
+            p = subprocess.Popen(
+                command,
+                stdout=subprocess.PIPE,
+                stderr=None,
+                stdin=subprocess.PIPE,
+                universal_newlines=True,
+            )
+        except OSError as e:
+            # Give the user more context when clang-format isn't
+            # found/isn't executable, etc.
+            raise RuntimeError(
+                'Failed to run "%s" - %s"' % (" ".join(command), e.strerror)
+            )
+
+        stdout, _stderr = p.communicate()
+        if p.returncode != 0:
+            return p.returncode
+
+        if not args.i:
+            with open(filename) as f:
+                code = f.readlines()
+            formatted_code = StringIO(stdout).readlines()
+            diff = difflib.unified_diff(
+                code,
+                formatted_code,
+                filename,
+                filename,
+                "(before formatting)",
+                "(after formatting)",
+            )
+            diff_string = "".join(diff)
+            if len(diff_string) > 0:
+                has_diff = True
+                sys.stdout.write(diff_string)
+
+    if has_diff:
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())

.github/workflows/format-check.yml

@@ -0,0 +1,47 @@
+name: Formatting check
+
+on: [pull_request]
+
+jobs:
+  formatting-check:
+    name: Formatting check
+    runs-on: ubuntu-24.04
+
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        # To get a diff from the PR we need to fetch 2 commits.
+        # The checkout action will create a merge commit as {{ github.sha }}.
+        fetch-depth: 2
+
+    - name: Install dependencies
+      run: |
+        sudo apt-get update
+        sudo apt-get install -yqq clang-format-18
+
+    - name: Format check
+      id: format-check
+      run: |
+        git diff -U0 --no-color ${{ github.sha }}^ -- '*.cpp' '*.c' '*.h' '*.hpp' |
+          ./.github/workflows/clang-format-diff.py -p1 -binary clang-format-18 > clang-format.patch || true
+
+        # Check if patch is not empty
+        if [ -s clang-format.patch ]; then
+          echo "###############################################################"
+          echo "# Format checks failed!"
+          echo "# A patch has been uploaded as an artifact and is shown below."
+          echo "###############################################################"
+
+          # Show patch
+          cat clang-format.patch
+
+          exit 1
+        fi
+
+    - name: Upload format fixes patch 
+      uses: actions/upload-artifact@v4
+      if: ${{ failure() && steps.format-check.outcome == 'failure' }}
+      with:
+        name: clang-format.patch
+        path: clang-format.patch
+        if-no-files-found: ignore