build/clobber.py

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