Unify gyp rules for running protoc.

build/protoc.gypi

+# Copyright (c) 2011 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 an 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',
+#   'sources': [
+#     'foo.proto',
+#     'bar.proto',
+#   ],
+#   'variables': {
+#     'proto_in_dir': '.'
+#     'proto_out_dir': 'dir/for/my_proto_lib'
+#   },
+#   'includes': ['path/to/this/gypi/file'],
+# }
+# If necessary, you may add normal .cc files to the sources list or other gyp
+# dependencies.  The proto headers are guaranteed to be generated before any
+# source files, even within this target, are compiled.
+#
+# The 'proto_in_dir' variable must be the relative path to the
+# directory containing the .proto files.
+#
+# The 'proto_out_dir' variable specifies the path suffix that output
+# files are generated under.  Targets that gyp-depend on my_proto_lib
+# will be able to include the resulting proto headers with an include
+# 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': '<(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)',

[TVL, 2011/08/18 20:56:50]

'proto_in_dir?': '.'

if it's common?

[Evan Martin, 2011/08/18 21:12:43]

Did you mean %?  The only use of '?' I could find was this:
http://codesearch.google.com/codesearch#OAMlx_jo-ck/src/testing/gtest.gyp&exa...

Seems to work, PTAL

[TVL, 2011/08/19 13:18:27]

Yes, sorry.

+  },
+  'rules': [
+    {
+      'rule_name': 'genproto',
+      'extension': 'proto',
+      'inputs': [
+        '<(protoc)',
+      ],
+      'outputs': [
+        '<(py_dir)/<(RULE_INPUT_ROOT)_pb2.py',
+        '<(cc_dir)/<(RULE_INPUT_ROOT).pb.cc',
+        '<(cc_dir)/<(RULE_INPUT_ROOT).pb.h',
+      ],
+      'action': [
+        '<(protoc)',
+        '--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)',
+        ],
+      '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',
+  ],
+  'direct_dependent_settings': {
+    'include_dirs': [
+      '<(SHARED_INTERMEDIATE_DIR)/protoc_out',
+    ]
+  },
+  # This target exports a hard dependency because it generates header
+  # files.
+  'hard_dependency': 1,
+}