CrOS: Convert MediaTransferProtocolDaemonClient to use protobufs.

build/protoc.gypi

 # 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.
 
 # This file is meant to be included into a target to provide a rule
 # to invoke protoc in a consistent manner.
 #
 # To use this, create a gyp target with the following form:
 # {
 #   'target_name': 'my_proto_lib',
@@ skipping 21 matching lines @@
 # like:
 #   #include "dir/for/my_proto_lib/foo.pb.h"
 #
 # Implementation notes:
 # A proto_out_dir of foo/bar produces
 #   <(SHARED_INTERMEDIATE_DIR)/protoc_out/foo/bar/{file1,file2}.pb.{cc,h}
 #   <(SHARED_INTERMEDIATE_DIR)/pyproto/foo/bar/{file1,file2}_pb2.py
 
 {
   'variables': {
+    'protoc_wrapper': '<(DEPTH)/tools/protoc_wrapper/protoc_wrapper.py',
     'protoc': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)protoc<(EXECUTABLE_SUFFIX)',
     'cc_dir': '<(SHARED_INTERMEDIATE_DIR)/protoc_out/<(proto_out_dir)',
     'py_dir': '<(PRODUCT_DIR)/pyproto/<(proto_out_dir)',
+    'cc_extra%': '',

[Ryan Sleevi, 2012/09/12 19:47:32]

Please add documentation about cc_extra and cc_include to the above comment.

I'd also suggest renaming cc_extra to be more indicative of its purpose (unless
this is what protoc also calls it?)

+    'cc_include%': '',
     'proto_in_dir%': '.',
   },
   'rules': [
     {
       'rule_name': 'genproto',
       'extension': 'proto',
       'inputs': [
+        '<(protoc_wrapper)',
         '<(protoc)',
       ],
       'outputs': [
         '<(py_dir)/<(RULE_INPUT_ROOT)_pb2.py',
         '<(cc_dir)/<(RULE_INPUT_ROOT).pb.cc',
         '<(cc_dir)/<(RULE_INPUT_ROOT).pb.h',
       ],
       'action': [
+        'python',
+        '<(protoc_wrapper)',
+        '<(cc_include)' ':' '<(cc_dir)/<(RULE_INPUT_ROOT).pb.h',

[Ryan Sleevi, 2012/09/12 19:47:32]

If no 'cc_include' is specified, this expands to an argument of :foo/bar.pb.h

Unfortunately, because this is a GYPI that is included by multiple targets, it's
not "cleanly" possible to use nested variables to create some 'cc_include_flag'
meta-variable.

Further, Nico's been working on supporting ':' in filenames in Ninja, so I'm not
sure using ':' as a delimiter is wise.

Finally, concatenating strings like GYP in this way is not really a 'supported'
or 'good' way, it just happens to work as a side-effect of how Python's parsing
things. The correct form would be:
'<(cc_include):<(cc_dir)/<(RULE_INPUT_ROOT).pb.h' (although, like I said, using
':' isn't that good here. This string concatenation note also applies to line
74.

My recommendation, for those reasons, is to make the cc_include and the pb.h
flagged arguments to protoc_wrapper. eg:

--include_file (path_or_null)
--protobuf_file (path)
-- (used by the Python script to say 'ignore all that follows')
(protoc command to execute and remaining args)

         '<(protoc)',
         # Using the --arg val form (instead of --arg=val) allows gyp's msvs rule
         # generation to correct 'val' which is a path.
         '--proto_path','<(proto_in_dir)',
         # Naively you'd use <(RULE_INPUT_PATH) here, but protoc requires
         # --proto_path is a strict prefix of the path given as an argument.
         '<(proto_in_dir)/<(RULE_INPUT_ROOT)<(RULE_INPUT_EXT)',
-        '--cpp_out','<(cc_dir)',
-        '--python_out','<(py_dir)',
+        '--cpp_out', '<(cc_extra)' '<(cc_dir)',
+        '--python_out', '<(py_dir)',
         ],
       'msvs_cygwin_shell': 0,
       'message': 'Generating C++ and Python code from <(RULE_INPUT_PATH)',
       'process_outputs_as_sources': 1,
     },
   ],
   'dependencies': [
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protoc#host',
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
   ],
   'include_dirs': [
     '<(SHARED_INTERMEDIATE_DIR)/protoc_out',
+    '<(DEPTH)',
   ],
   'direct_dependent_settings': {
     'include_dirs': [
       '<(SHARED_INTERMEDIATE_DIR)/protoc_out',
     ]
   },
   'export_dependent_settings': [
     # The generated headers reference headers within protobuf_lite,
     # so dependencies must be able to find those headers too.
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
   ],
   # This target exports a hard dependency because it generates header
   # files.
   'hard_dependency': 1,
 }