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1#!/usr/bin/env python
2# Copyright 2015 The Chromium Authors. All rights reserved.
3# Use of this source code is governed by a BSD-style license that can be
4# found in the LICENSE file.
5
6"""This script provides methods for clobbering build directories."""
7
8import argparse
9import os
10import shutil
11import subprocess
12import sys
13
14
15def extract_gn_build_commands(build_ninja_file):
16  """Extracts from a build.ninja the commands to run GN.
17
18  The commands to run GN are the gn rule and build.ninja build step at the
19  top of the build.ninja file. We want to keep these when deleting GN builds
20  since we want to preserve the command-line flags to GN.
21
22  On error, returns the empty string."""
23  result = ""
24  with open(build_ninja_file, 'r') as f:
25    # Read until the second blank line. The first thing GN writes to the file
26    # is the "rule gn" and the second is the section for "build build.ninja",
27    # separated by blank lines.
28    num_blank_lines = 0
29    while num_blank_lines < 2:
30      line = f.readline()
31      if len(line) == 0:
32        return ''  # Unexpected EOF.
33      result += line
34      if line[0] == '\n':
35        num_blank_lines = num_blank_lines + 1
36  return result
37
38
39def delete_dir(build_dir):
40  # For unknown reasons (anti-virus?) rmtree of Chromium build directories
41  # often fails on Windows.
42  if sys.platform.startswith('win'):
43    subprocess.check_call(['rmdir', '/s', '/q', build_dir], shell=True)
44  else:
45    shutil.rmtree(build_dir)
46
47
48def delete_build_dir(build_dir):
49  # GN writes a build.ninja.d file. Note that not all GN builds have args.gn.
50  build_ninja_d_file = os.path.join(build_dir, 'build.ninja.d')
51  if not os.path.exists(build_ninja_d_file):
52    delete_dir(build_dir)
53    return
54
55  # GN builds aren't automatically regenerated when you sync. To avoid
56  # messing with the GN workflow, erase everything but the args file, and
57  # write a dummy build.ninja file that will automatically rerun GN the next
58  # time Ninja is run.
59  build_ninja_file = os.path.join(build_dir, 'build.ninja')
60  build_commands = extract_gn_build_commands(build_ninja_file)
61
62  try:
63    gn_args_file = os.path.join(build_dir, 'args.gn')
64    with open(gn_args_file, 'r') as f:
65      args_contents = f.read()
66  except IOError:
67    args_contents = ''
68
69  delete_dir(build_dir)
70
71  # Put back the args file (if any).
72  os.mkdir(build_dir)
73  if args_contents != '':
74    with open(gn_args_file, 'w') as f:
75      f.write(args_contents)
76
77  # Write the build.ninja file sufficiently to regenerate itself.
78  with open(os.path.join(build_dir, 'build.ninja'), 'w') as f:
79    if build_commands != '':
80      f.write(build_commands)
81    else:
82      # Couldn't parse the build.ninja file, write a default thing.
83      f.write('''rule gn
84command = gn -q gen //out/%s/
85description = Regenerating ninja files
86
87build build.ninja: gn
88generator = 1
89depfile = build.ninja.d
90''' % (os.path.split(build_dir)[1]))
91
92  # Write a .d file for the build which references a nonexistant file. This
93  # will make Ninja always mark the build as dirty.
94  with open(build_ninja_d_file, 'w') as f:
95    f.write('build.ninja: nonexistant_file.gn\n')
96
97
98def clobber(out_dir):
99  """Clobber contents of build directory.
100
101  Don't delete the directory itself: some checkouts have the build directory
102  mounted."""
103  for f in os.listdir(out_dir):
104    path = os.path.join(out_dir, f)
105    if os.path.isfile(path):
106      os.unlink(path)
107    elif os.path.isdir(path):
108      delete_build_dir(path)
109
110
111def main():
112  parser = argparse.ArgumentParser()
113  parser.add_argument('out_dir', help='The output directory to clobber')
114  args = parser.parse_args()
115  clobber(args.out_dir)
116  return 0
117
118
119if __name__ == '__main__':
120  sys.exit(main())
121