Check formatting without files modification

Change-Id: I1145214874ec9ed7d18e93173e9462f096025d35

scripts/format.py

@@ -21,10 +21,12 @@
 #
 
 import argparse
+import difflib
 import glob
 import logging
 import os
 import subprocess
+import sys
 from concurrent.futures import ThreadPoolExecutor
 from itertools import repeat
 
@@ -38,12 +40,48 @@ def main():
     logging.info('Finding source files')
     files = find_source_files(args.root_directory)
 
+    if args.check:
+        return check_formatting(files, args.clang_format)
+    else:
+        return format_files(files, args.clang_format)
+
+
+def check_formatting(files, clang_format):
+    logging.info('Checking formatting')
+    with ThreadPoolExecutor() as executor:
+        logging.info('Reading expected values')
+        expected = executor.map(run_clang_format_star,
+                                zip(files,
+                                    repeat(clang_format)))
+
+        logging.info('Reading actual values')
+        actual = executor.map(read_file, files)
+
+        logging.info('Comparing')
+        diff_results = executor.map(diff_star, zip(actual, expected))
+
+    diffs = []
+    for f, d in zip(files, diff_results):
+        diff_str = '\n'.join(d)
+        if diff_str:
+            logging.warning('Diff in {}:\n{}'.format(f, diff_str))
+            diffs.append(f)
+        else:
+            logging.debug('No diff in {}'.format(f))
+
+    logging.info('Formatting checked')
+    logging.info('Diff count: {}'.format(len(diffs)))
+    return len(diffs)
+
+
+def format_files(files, clang_format):
     logging.info('Running clang-format')
     with ThreadPoolExecutor() as executor:
         executor.map(run_clang_format_star,
-                     zip(files, repeat(args.clang_format)))
-
+                     zip(files, repeat(clang_format),
+                         repeat('-i')))
     logging.info('Formatting is done')
+    return 0
 
 
 def find_source_files(root_path):
@@ -57,12 +95,26 @@ def find_source_files(root_path):
 
 
 def run_clang_format_star(args):
-    run_clang_format(*args)
+    return run_clang_format(*args)
+
+
+def run_clang_format(f, command='clang-format', arguments=''):
+    cmd = '{} {} {}'.format(command, arguments, f)
+    return subprocess.run(cmd, shell=True, check=True, stdout=subprocess.PIPE,
+                          stderr=subprocess.STDOUT).stdout.decode()
+
+
+def read_file(f):
+    with open(f) as f_content:
+        return f_content.read()
+
+
+def diff_star(args):
+    return diff(*args)
 
 
-def run_clang_format(f, command='clang-format'):
-    cmd = '{} -i {}'.format(command, f)
-    subprocess.run(cmd, shell=True, check=True)
+def diff(actual, expected):
+    return difflib.unified_diff(actual.splitlines(), expected.splitlines())
 
 
 def process_command_line():
@@ -71,8 +123,10 @@ def process_command_line():
                         help='Root directory of compute-samples source')
     parser.add_argument('--clang-format', default='clang-format',
                         help='clang-format command')
+    parser.add_argument('--check', action='store_true',
+                        help='Check formatting')
     return parser.parse_args()
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())