Add support for generating jars from protos and add cacheinvalidation_java.

build/protoc_java.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

[Ryan Sleevi, 2012/10/29 08:36:36]

We generate Python and C++ files using the single protoc.gypi.

It's worth exploring why this cannot be shared, and at least documenting in this
CL's change notes or in the file.

[nyquist, 2012/10/30 00:30:32]

Done.

+# to invoke protoc in a consistent manner.
+#
+# To use this, create a gyp target with the following form:
+# {
+#   'target_name': 'my_proto_lib',
+#   'type': 'static_library',

[Ryan Sleevi, 2012/10/29 08:36:36]

This is not correct, is it? Can you generate a static_library target from just
jar files?

[nyquist, 2012/10/30 00:30:32]

Change to 'none'.

+#   'sources': [
+#     'foo.proto',
+#     'bar.proto',
+#   ],
+#   'variables': {
+#     'proto_in_dir': '.'
+#     'output_java_files': [
+#       '>(java_out_dir)/org/chromium/package/Foo.java',
+#       '>(java_out_dir)/org/chromium/package/Bar.java'

[Ryan Sleevi, 2012/10/29 08:36:36]

Is there ever a situation where you have .proto files belonging to multiple
packages? Does it make more sense to have the package specified in the variable,
rather than requiring every source to be repeated?

[nyquist, 2012/10/30 00:30:32]

Removed the shole notion of specifying the .java-files and now instead generate
a .jar-file.

+#     ],
+#   },
+#   'includes': ['path/to/this/gypi/file'],
+# }
+#
+# The 'proto_in_dir' variable must be the relative path to the
+# directory containing the .proto files.  If left out, it defaults to '.'.
+#
+# The 'output_java_files' variable specifies a list of output files that will
+# be generated. It is based on the package and java_outer_classname fields in
+# the proto. All the values must be prefixed with >(java_out_dir), since that
+# is the root directory of all the output.
+#
+# Implementation notes:
+# A target_name of foo and proto-specified 'package' java.package.path produces:
+#   <(PRODUCT_DIR)/javaproto/foo/{java/package/path/}{Foo,Bar}.java
+# where Foo and Bar are taken from 'java_outer_classname' of the protos.
+
+{
+  'variables': {
+    'protoc': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)protoc<(EXECUTABLE_SUFFIX)',
+    'java_out_dir': '<(PRODUCT_DIR)/javaproto/<(_target_name)/src',
+    'proto_in_dir%': '.',
+  },
+  'actions': [
+    {
+      'action_name': 'genproto_java_output_dirs',
+      'inputs' : [],
+      'outputs': [
+        '<(java_out_dir)'
+      ],
+      'action': [ 'mkdir', '-p', '<(java_out_dir)' ],

[Ryan Sleevi, 2012/10/29 08:36:36]

NACK on this. I strongly dislike embedding platform-specific commands in GYP -
particularly when they just make directories.

Seems like this should be done in protoc or in a wrapper script, but not within
GYP. For example, Android supports an NDK on Windows - thus it's reasonable to
imagine building this on Windows at some point in the future.

[nyquist, 2012/10/30 00:30:32]

Changed to use .sh file. This is also used for timestamping output.

+    },
+    {
+      'action_name': 'genproto_java',
+      'inputs': [
+        '<(protoc)',
+        '<@(_sources)',
+      ],
+      'outputs': [
+        '<@(output_java_files)',
+      ],
+      'action': [
+        '<(protoc)',
+        '--proto_path','<(proto_in_dir)',
+        '<@(_sources)',
+        '--java_out', '<(java_out_dir)',
+      ],
+      'message': 'Generating Java code from <(proto_in_dir)',
+    },
+  ],
+  'dependencies': [
+    '<(DEPTH)/third_party/protobuf/protobuf.gyp:protoc#host',
+    '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
+  ],
+  'include_dirs': [
+    '<(SHARED_INTERMEDIATE_DIR)/protoc_out',

[Ryan Sleevi, 2012/10/29 08:36:36]

Why are either of these necessary at all? You're generating a Java target. You
never use the path protoc_out in this file.

[nyquist, 2012/10/30 00:30:32]

Done.

+    '<(DEPTH)',
+  ],
+  'direct_dependent_settings': {
+    'variables': {
+      'generated_src_dirs': ['<(java_out_dir)'],
+      'additional_input_paths': ['<@(_sources)'],
+    },
+  },
+}