[clang-tidy] Force LF newlines when writing files

[LegalizeAdulthood]

Summary

The recommendation on Windows is to checkout from git with
core.autolf=false in order to preserve LF line endings on
test files. However, when creating a new check this results
in modified files as having switched all the line endings on
Windows. Write all files with explicit LF line endings to
prevent this.

Fixes #52968

[• Quuxplusone]

LGTM FWIW.
I might even wonder why this code is using io.open instead of just plain open. (I didn't know io.open was a thing; StackOverflow tells me that it was something in Python2 but that in Python3 it's a synonym for open.)

[aaron.ballman]

LGTM, thanks!

clang-tools-extra/clang-tidy/add_new_check.py

def adapt_cmake(module_path, check_name_camel):
   cpp_file = check_name_camel + '.cpp'
 
   # Figure out whether this check already exists.
   for line in lines:
     if line.strip() == cpp_file:
       return False
 
   print('Updating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     cpp_found = False
     file_added = False
     for line in lines:
       cpp_line = line.strip().endswith('.cpp')
       if (not file_added) and (cpp_line or cpp_found):
         cpp_found = True
         if (line.strip() > cpp_file) or (not cpp_line):
           f.write('  ' + cpp_file + '\n')
           file_added = True
       f.write(line)
 
   return True
 
 
 # Adds a header for the new check.
 def write_header(module_path, module, namespace, check_name, check_name_camel):
   check_name_dashes = module + '-' + check_name
   filename = os.path.join(module_path, check_name_camel) + '.h'
   print('Creating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     header_guard = ('LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_' + module.upper() + '_'
                     + check_name_camel.upper() + '_H')
     f.write('//===--- ')
     f.write(os.path.basename(filename))
     f.write(' - clang-tidy ')
     f.write('-' * max(0, 42 - len(os.path.basename(filename))))
     f.write('*- C++ -*-===//')
     f.write("""
""" % {'header_guard': header_guard,
        'module': module,
        'namespace': namespace})
 
 
 # Adds the implementation of the new check.
 def write_implementation(module_path, module, namespace, check_name_camel):
   filename = os.path.join(module_path, check_name_camel) + '.cpp'
   print('Creating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     f.write('//===--- ')
     f.write(os.path.basename(filename))
     f.write(' - clang-tidy ')
     f.write('-' * max(0, 51 - len(os.path.basename(filename))))
     f.write('-===//')
     f.write("""
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
def adapt_module(module_path, module, check_name, check_name_camel):
   modulecpp = list(filter(
       lambda p: p.lower() == module.lower() + 'tidymodule.cpp',
       os.listdir(module_path)))[0]
   filename = os.path.join(module_path, modulecpp)
   with io.open(filename, 'r', encoding='utf8') as f:
     lines = f.readlines()
 
   print('Updating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     header_added = False
     header_found = False
     check_added = False
     check_fq_name = module + '-' + check_name
     check_decl = ('    CheckFactories.registerCheck<' + check_name_camel +
                   '>(\n        "' + check_fq_name + '");\n')
 
     lines = iter(lines)
def add_release_notes(module_path, module, check_name):
   with io.open(filename, 'r', encoding='utf8') as f:
     lines = f.readlines()
 
   lineMatcher = re.compile('New checks')
   nextSectionMatcher = re.compile('New check aliases')
   checkMatcher = re.compile('- New :doc:`(.*)')
 
   print('Updating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     note_added = False
     header_found = False
     add_note_here = False
 
     for line in lines:
       if not note_added:
         match = lineMatcher.match(line)
         match_next = nextSectionMatcher.match(line)

 
 
 # Adds a test for the check.
 def write_test(module_path, module, check_name, test_extension):
   check_name_dashes = module + '-' + check_name
   filename = os.path.normpath(os.path.join(module_path, '../../test/clang-tidy/checkers',
                                            check_name_dashes + '.' + test_extension))
   print('Creating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     f.write("""// RUN: %%check_clang_tidy %%s %(check_name_dashes)s %%t
 
 // FIXME: Add something that triggers the check here.
 void f();
 // CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'f' is insufficiently awesome [%(check_name_dashes)s]
 
 // FIXME: Verify the applied fix.
 //   * Make the CHECK patterns specific enough and try to make verified lines
if match and check_name:
         'autofix': has_auto_fix(match.group(1))
       }
     return ''
 
   checks = map(format_link, doc_files)
   checks_alias = map(format_link_alias, doc_files)
 
   print('Updating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     for line in lines:
       f.write(line)
       if line.strip() == ".. csv-table::":
         # We dump the checkers
         f.write('   :header: "Name", "Offers fixes"\n\n')
         f.writelines(checks)
         # and the aliases
         f.write('\n\n')
         f.write('.. csv-table:: Aliases..\n')
         f.write('   :header: "Name", "Redirect", "Offers fixes"\n\n')
         f.writelines(checks_alias)
         break
 
 
 # Adds a documentation for the check.
 def write_docs(module_path, module, check_name):
   check_name_dashes = module + '-' + check_name
   filename = os.path.normpath(os.path.join(
       module_path, '../../docs/clang-tidy/checks/', check_name_dashes + '.rst'))
   print('Creating %s...' % filename)
-  with io.open(filename, 'w', encoding='utf8') as f:
+  with io.open(filename, 'w', encoding='utf8', newline='\n') as f:
     f.write(""".. title:: clang-tidy - %(check_name_dashes)s
 
 %(check_name_dashes)s
 %(underline)s
 
 FIXME: Describe what patterns does the check detect and why. Give examples.
 """ % {'check_name_dashes': check_name_dashes,
        'underline': '=' * len(check_name_dashes)})