[clang-format] add support for cppm files

[MyDeveloperDay]

Summary

C++20 Modules current style is to assign a new file suffix .cppm.

https://github.com/llvm/llvm-project/issues/52658

Ensure git-clang-format can handle that as a default extension

[ChuanqiXu]

Thanks for the quick respond!

A note in the summary:

- C++20 Modules current style is to assign a new file suffix .cppm instead of .cpp and .h
+ C++20 Modules current style is to assign a new file suffix .cppm.

Since *.cpp and *.h is not deprecated.

[MyDeveloperDay]

clang/tools/clang-format/git-clang-format

81–82

I missed a , here I think

[MyDeveloperDay]

Missed a comma

[curdeius]

LGTM.

clang/tools/clang-format/clang-format-diff.py

50–51

Nit: I would put it close to other C++ extensions.

[MyDeveloperDay]

Move cppm to be with other cxx extensions

[rsmith]

FWIW, Clang also supports .ccm, .cxxm, and .c++m. See https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/Types.cpp#L273

[MyDeveloperDay]

Add other support module file types for completeness

clang/tools/clang-format/clang-format-diff.py

def main():
   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|c|cl|h|hh|hpp|hxx|m|mm|inc|js|ts'
-                      r'|proto|protodevel|java|cs|json)',
+                      r'.*\.(cpp|cc|c\+\+|cxx|cppm|ccm|cxxm|c\+\+m|c|cl|h|hh|hpp|hxx'
+                      r'|m|mm|inc|js|ts|proto|protodevel|java|cs|json)',
                       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, '

clang/tools/clang-format/git-clang-format

else:
     dash_dash = argv[idx:]
     argv = argv[:idx]
 
   default_extensions = ','.join([
       # From clang/lib/Frontend/FrontendOptions.cpp, all lower case
       'c', 'h',  # C
       'm',  # ObjC
       'mm',  # ObjC++
       'cc', 'cp', 'cpp', 'c++', 'cxx', 'hh', 'hpp', 'hxx',  # C++
+      'ccm', 'cppm', 'cxxm', 'c++m',  # C++ Modules
       'cu', 'cuh',  # CUDA
       # Other languages that clang-format supports
       'proto', 'protodevel',  # Protocol Buffers
       'java',  # Java
       'js',  # JavaScript
       'ts',  # TypeScript
       'cs',  # C Sharp
       'json',  # Json