Do not perform a non-incremental compile when previous compile failed.

build/android/gyp/util/md5_check.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import difflib
 import hashlib
 import itertools
 import json
 import os
 import sys
 import zipfile
 
 
 # When set and a difference is detected, a diff of what changed is printed.
 _PRINT_MD5_DIFFS = int(os.environ.get('PRINT_MD5_DIFFS', 0))
 
+# An escape hatch that causes all targets to be rebuilt.
+_FORCE_REBUILD = int(os.environ.get('FORCE_REBUILD', 0))
+
 
 def CallAndRecordIfStale(
     function, record_path=None, input_paths=None, input_strings=None,
     output_paths=None, force=False, pass_changes=False):
   """Calls function if outputs are stale.
 
   Outputs are considered stale if:
   - any output_paths are missing, or
   - the contents of any file within input_paths has changed, or
   - the contents of input_strings has changed.
@@ skipping 26 matching lines @@
   new_metadata.AddStrings(input_strings)
 
   for path in input_paths:
     if _IsZipFile(path):
       entries = _ExtractZipEntries(path)
       new_metadata.AddZipFile(path, entries)
     else:
       new_metadata.AddFile(path, _Md5ForPath(path))
 
   old_metadata = None
+  force = force or _FORCE_REBUILD
   missing_outputs = [x for x in output_paths if force or not os.path.exists(x)]
   # When outputs are missing, don't bother gathering change information.
   if not missing_outputs and os.path.exists(record_path):
     with open(record_path, 'r') as jsonfile:
       try:
         old_metadata = _Metadata.FromFile(jsonfile)
       except:  # pylint: disable=bare-except
         pass  # Not yet using new file format.
 
   changes = Changes(old_metadata, new_metadata, force, missing_outputs)
   if not changes.HasChanges():
     return
 
   if _PRINT_MD5_DIFFS:
     print '=' * 80
     print 'Target is stale: %s' % record_path
     print changes.DescribeDifference()
     print '=' * 80
 
-  # Delete the old metdata beforehand since failures leave it in an
-  # inderterminate state.
-  if old_metadata:
-    os.unlink(record_path)
-
   args = (changes,) if pass_changes else ()
   function(*args)
 
   with open(record_path, 'w') as f:
     new_metadata.ToFile(f)
 
 
 class Changes(object):
   """Provides and API for querying what changed between runs."""
 
@@ skipping 293 matching lines @@
 
 def _ExtractZipEntries(path):
   """Returns a list of (path, CRC32) of all files within |path|."""
   entries = []
   with zipfile.ZipFile(path) as zip_file:
     for zip_info in zip_file.infolist():
       # Skip directories and empty files.
       if zip_info.CRC:
         entries.append((zip_info.filename, zip_info.CRC))
   return entries