Trigger a landmine on first-time landmine deployment.

build/landmines.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 This script runs every build as the first hook (See DEPS). If it detects that
 the build should be clobbered, it will delete the contents of the build
 directory.
 
@@ skipping 114 matching lines @@
 generator = 1
 depfile = build.ninja.d
 ''' % (os.path.split(build_dir)[1]))
 
   # Write a .d file for the build which references a nonexistant file. This
   # will make Ninja always mark the build as dirty.
   with open(build_ninja_d_file, 'w') as f:
     f.write('build.ninja: nonexistant_file.gn\n')
 
 
-def clobber_if_necessary(new_landmines):
-  """Does the work of setting, planting, and triggering landmines."""
-  out_dir = get_build_dir(landmine_utils.builder())
-  landmines_path = os.path.normpath(os.path.join(out_dir, '..', '.landmines'))
-  try:
-    os.makedirs(out_dir)
-  except OSError as e:
-    if e.errno == errno.EEXIST:
-      pass
-
+def needs_clobber(landmines_path, new_landmines):
   if os.path.exists(landmines_path):
     with open(landmines_path, 'r') as f:
       old_landmines = f.readlines()
     if old_landmines != new_landmines:
       old_date = time.ctime(os.stat(landmines_path).st_ctime)
       diff = difflib.unified_diff(old_landmines, new_landmines,
           fromfile='old_landmines', tofile='new_landmines',
           fromfiledate=old_date, tofiledate=time.ctime(), n=0)
       sys.stdout.write('Clobbering due to:\n')
       sys.stdout.writelines(diff)
+      return True
+  else:
+    sys.stdout.write('Clobbering due to missing landmines file.\n')
+    return True
+  return False
 
-      # Clobber contents of build directory but not directory itself: some
-      # checkouts have the build directory mounted.
-      for f in os.listdir(out_dir):
-        path = os.path.join(out_dir, f)
-        # Soft version of chromium's clobber. Only delete directories not files
-        # as e.g. on windows the output dir is the build dir that shares some
-        # checked out files.
-        if os.path.isdir(path) and re.search(r"(?:[Rr]elease)|(?:[Dd]ebug)", f):
-          delete_build_dir(path)
+
+def clobber_if_necessary(new_landmines):
+  """Does the work of setting, planting, and triggering landmines."""
+  out_dir = get_build_dir(landmine_utils.builder())
+  landmines_path = os.path.normpath(os.path.join(out_dir, '..', '.landmines'))
+  try:
+    os.makedirs(out_dir)
+  except OSError as e:
+    if e.errno == errno.EEXIST:
+      pass
+
+  if needs_clobber(landmines_path, new_landmines):
+    # Clobber contents of build directory but not directory itself: some
+    # checkouts have the build directory mounted.
+    for f in os.listdir(out_dir):
+      path = os.path.join(out_dir, f)
+      # Soft version of chromium's clobber. Only delete directories not files
+      # as e.g. on windows the output dir is the build dir that shares some
+      # checked out files.
+      if os.path.isdir(path) and re.search(r"(?:[Rr]elease)|(?:[Dd]ebug)", f):
+        delete_build_dir(path)
 
   # Save current set of landmines for next time.
   with open(landmines_path, 'w') as f:
     f.writelines(new_landmines)
 
 
 def process_options():
   """Returns a list of landmine emitting scripts."""
   parser = optparse.OptionParser()
   parser.add_option(
@@ skipping 36 matching lines @@
     proc = subprocess.Popen([sys.executable, s], stdout=subprocess.PIPE)
     output, _ = proc.communicate()
     landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
   clobber_if_necessary(landmines)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())