clang-format hook support --verbose output

README.md

@@ -151,6 +151,21 @@ Use -header-filter=.* to display errors from all non-system headers. Use -system
 
 ```
 
+## Troubleshooting
+
+### Debugging `clang-format` hook
+
+If you encounter issues with the clang-format hook (such as exit code 247 or other errors), you can enable verbose output to show the list of processed files.
+
+```yaml
+repos:
+  - repo: https://github.com/cpp-linter/cpp-linter-hooks
+    rev: v0.8.1
+    hooks:
+      - id: clang-format
+        args: [--style=file, --version=18, --verbose]   # Add --verbose for detailed output
+```
+
 ## Contributing
 
 We welcome contributions! Whether it's fixing issues, suggesting improvements, or submitting pull requests, your support is greatly appreciated.

cpp_linter_hooks/clang_format.py

@@ -7,6 +7,9 @@
 
 parser = ArgumentParser()
 parser.add_argument("--version", default=DEFAULT_CLANG_VERSION)
+parser.add_argument(
+    "-v", "--verbose", action="store_true", help="Enable verbose output"
+)
 
 
 def run_clang_format(args=None) -> Tuple[int, str]:

testing/pre-commit-config-verbose.yaml

@@ -0,0 +1,6 @@
+repos:
+  - repo: .
+    rev: HEAD
+    hooks:
+      - id: clang-format
+        args: [--style=file, --version=16, --verbose]  # test with verbose output

testing/run.sh

@@ -1,7 +1,7 @@
 rm -f result.txt
 git restore testing/main.c
 
-for config in testing/pre-commit-config.yaml testing/pre-commit-config-version.yaml; do
+for config in testing/pre-commit-config.yaml testing/pre-commit-config-version.yaml testing/pre-commit-config-verbose.yaml; do
     pre-commit clean
     pre-commit run -c $config --files testing/main.c | tee -a result.txt || true
     git restore testing/main.c

tests/test_clang_format.py

@@ -64,3 +64,35 @@ def test_run_clang_format_dry_run(args, expected_retval, tmp_path):
     test_file = tmp_path / "main.c"
     ret, _ = run_clang_format(["--dry-run", str(test_file)])
     assert ret == -1  # Dry run should not fail
+
+
+def test_run_clang_format_verbose(tmp_path):
+    """Test that verbose option works and provides detailed output."""
+    # copy test file to tmp_path to prevent modifying repo data
+    test_file = tmp_path / "main.c"
+    test_file.write_bytes(Path("testing/main.c").read_bytes())
+
+    # Test with verbose flag
+    ret, output = run_clang_format(["--verbose", "--style=Google", str(test_file)])
+
+    # Should succeed
+    assert ret == 0
+    # Should have verbose output (will be printed to stderr, not returned)
+    # The function should still return successfully
+    assert test_file.read_text() == Path("testing/good.c").read_text()
+
+
+def test_run_clang_format_verbose_error(tmp_path):
+    """Test that verbose option provides useful error information."""
+    test_file = tmp_path / "main.c"
+    test_file.write_bytes(Path("testing/main.c").read_bytes())
+
+    # Test with verbose flag and invalid style
+    ret, output = run_clang_format(
+        ["--verbose", "--style=InvalidStyle", str(test_file)]
+    )
+
+    # Should fail
+    assert ret != 0
+    # Should have error message in output
+    assert "Invalid value for -style" in output