Linux: update protoc wrapper to allow building with system protobuf.

tools/protoc_wrapper/protoc_wrapper.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
-"""A simple wrapper for protoc to add includes in generated cpp headers."""
+"""
+A simple wrapper for protoc.
+
+- Adds includes in generated headers.
+- Handles building with system protobuf as an option.
+"""
 
 import optparse
+import os.path
+import shutil
 import subprocess
 import sys
+import tempfile
 
 PROTOC_INCLUDE_POINT = '// @@protoc_insertion_point(includes)\n'
 
 def ModifyHeader(header_file, extra_header):
   """Adds |extra_header| to |header_file|. Returns 0 on success.
 
   |extra_header| is the name of the header file to include.
   |header_file| is a generated protobuf cpp header.
   """
   include_point_found = False
   header_contents = []
   with open(header_file) as f:
     for line in f:
       header_contents.append(line)
       if line == PROTOC_INCLUDE_POINT:
         extra_header_msg = '#include "%s"\n' % extra_header
         header_contents.append(extra_header_msg)
         include_point_found = True;
   if not include_point_found:
     return 1
 
   with open(header_file, 'wb') as f:
     f.write(''.join(header_contents))
   return 0
 
 
+def RewriteProtoFilesForSystemProtobuf(path):
+  wrapper_dir = tempfile.mkdtemp()
+  try:
+    for filename in os.listdir(path):
+      if not filename.endswith('.proto'):
+        continue
+      with open(os.path.join(path, filename), 'r') as src_file:
+        with open(os.path.join(wrapper_dir, filename), 'w') as dst_file:
+          for line in src_file:
+            # Remove lines that break build with system protobuf.
+            # We cannot optimize for lite runtime, because system lite runtime
+            # does not have a Chromium-specific hack to retain unknown fields.
+            # Similarly, it does not understand corresponding option to control
+            # the usage of that hack.
+            if 'LITE_RUNTIME' in line or 'retain_unknown_fields' in line:
+              continue
+            dst_file.write(line)
+
+    return wrapper_dir
+  except:
+    shutil.rmtree(wrapper_dir)
+    raise
+
+
 def main(argv):
   parser = optparse.OptionParser()
   parser.add_option('--include', dest='extra_header',
                     help='The extra header to include. This must be specified '
                          'along with --protobuf.')
   parser.add_option('--protobuf', dest='generated_header',
                     help='The c++ protobuf header to add the extra header to. '
                          'This must be specified along with --include.')
+  parser.add_option('--proto-in-dir',
+                    help='The directory containing .proto files.')
+  parser.add_option('--proto-in-file', help='Input file to compile.')
+  parser.add_option('--use-system-protobuf', type=int, default=0,
+                    help='Option to use system-installed protobuf '
+                         'instead of bundled one.')
   (options, args) = parser.parse_args(sys.argv)
   if len(args) < 2:
     return 1
 
-  # Run what is hopefully protoc.
-  ret = subprocess.call(args[1:])
-  if ret != 0:
-    return ret
+  proto_path = options.proto_in_dir
+  if options.use_system_protobuf == 1:
+    proto_path = RewriteProtoFilesForSystemProtobuf(proto_path)
+  try:
+    # Run what is hopefully protoc.
+    protoc_args = args[1:]
+    protoc_args += ['--proto_path=%s' % proto_path,
+                    os.path.join(proto_path, options.proto_in_file)]
+    ret = subprocess.call(protoc_args)
+    if ret != 0:
+      return ret
+  finally:
+    if options.use_system_protobuf == 1:
+      # Remove temporary directory holding re-written files.
+      shutil.rmtree(proto_path)
 
   # protoc succeeded, check to see if the generated cpp header needs editing.
   if not options.extra_header or not options.generated_header:
     return 0
   return ModifyHeader(options.generated_header, options.extra_header)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))