GN proto_libary refactoring.

third_party/protobuf/proto_library.gni

 # Copyright 2014 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.
 
 # Compile a protocol buffer.
 #
 # Protobuf parameters:
 #
+#   proto_in_dir (optional)
+#       Specifies the path relative to the current BUILD.gn file where
+#       proto files are located and the directory structure of
+#       this proto library starts.
+#
+#       This option can be calculated automatically but it will raise an
+#       assertion error if any nested directories are found.
+#
 #   proto_out_dir (optional)
-#       Specifies the path suffix that output files are generated under. This
-#       path will be appended to the root_gen_dir.
-#
-#       Targets that depend on the proto target will be able to include the
-#       resulting proto headers with an include like:
-#         #include "dir/for/my_proto_lib/foo.pb.h"
-#       If undefined, this defaults to matching the input directory for each
-#       .proto file (you should almost always use the default mode).
+#       Specifies the path suffix that output files are generated under.
+#       This path will be appended to |root_gen_dir|, but for python stubs
+#       it will be appended to |root_build_dir|/pyproto.
 #
 #   generate_python (optional, default true)
 #       Generate Python protobuf stubs.
 #
 #   generate_cc (optional, default true)
 #       Generate C++ protobuf stubs.
 #
 #   cc_generator_options (optional)
 #       List of extra flags passed to the protocol compiler.  If you need to
 #       add an EXPORT macro to a protobuf's C++ header, set the
 #       'cc_generator_options' variable with the value:
 #       'dllexport_decl=FOO_EXPORT:' (note trailing colon).
 #
 #       It is likely you also need to #include a file for the above EXPORT
 #       macro to work (see cc_include) and set
 #       component_build_force_source_set = true.
 #
+#   cc_include (optional)
+#       String listing an extra include that should be passed.
+#       Example: cc_include = "foo/bar.h"
+#
 #   generator_plugin_label (optional)
 #       GN label for plugin executable which generates custom cc stubs.
+#       Don't specify a toolchain, host toolchain is assumed.
 #
-#   generator_plugin_suffix (required if generator_plugin_label set)
+#   generator_plugin_suffix (required if |generator_plugin_label| set)
 #       Suffix (before extension) for generated .cc and .h files.
 #
 #   generator_plugin_options (optional)
 #       Extra flags passed to the plugin. See cc_generator_options.
 #
-#   cc_include (optional)
-#       String listing an extra include that should be passed.
-#       Example: cc_include = "foo/bar.h"
-#
 #   deps (optional)
 #       Additional dependencies.
 #
 # Parameters for compiling the generated code:
 #
 #   component_build_force_source_set (Default=false)
 #       When set true the generated code will be compiled as a source set in
 #       the component build. This does not affect static builds.  If you are
 #       exporting symbols from a component, this is required to prevent those
 #       symbols from being stripped. If you're not using dllexports in
 #       cc_generator_options, it's usually best to leave this false.
 #
 #   defines (optional)
 #       Defines to supply to the source set that compiles the generated source
 #       code.
 #
 #   extra_configs (optional)
 #       A list of config labels that will be appended to the configs applying
 #       to the source set.
 #
-# Example
+# Example:
 #  proto_library("mylib") {
 #    sources = [
 #      "foo.proto",
 #    ]
 #  }
 
 template("proto_library") {
   assert(defined(invoker.sources), "Need sources for proto_library")
+  proto_sources = invoker.sources
 
   # Don't apply OS-specific sources filtering to the assignments later on.
   # Platform files should have gotten filtered out in the sources assignment
   # when this template was invoked. If they weren't, it was on purpose and
   # this template shouldn't re-apply the filter.
   set_sources_assignment_filter([])
 
+  if (defined(invoker.generate_cc)) {
+    generate_cc = invoker.generate_cc
+  } else {
+    generate_cc = true
+  }
+
+  if (defined(invoker.generate_python)) {
+    generate_python = invoker.generate_python
+  } else {
+    generate_python = true
+  }
+
+  if (defined(invoker.generator_plugin_label)) {
+    generator_plugin_label = invoker.generator_plugin_label
+    generator_plugin_suffix = invoker.generator_plugin_suffix
+    generate_with_plugin = true
+
+    # Straightforward way to get the name of executable doesn't work because
+    # |root_out_dir| and |root_build_dir| may differ in cross-compilation and
+    # also Windows executables have .exe at the end.
+
+    plugin_host_label = generator_plugin_label + "($host_toolchain)"
+    plugin_path = get_label_info(plugin_host_label, "root_out_dir") + "/" +
+                  get_label_info(plugin_host_label, "name")
+    if (host_os == "win") {
+      plugin_path += ".exe"
+    }
+    plugin_path = rebase_path(plugin_path, root_build_dir)
+  } else {
+    generate_with_plugin = false
+  }
+
+  if (defined(invoker.proto_in_dir)) {
+    proto_in_dir = invoker.proto_in_dir
+  } else {
+    proto_in_dir = get_path_info(proto_sources[0], "dir")
+
+    # Sanity check, |proto_in_dir| should be defined to allow sub-directories.
+    foreach(proto_source, proto_sources) {
+      assert(get_path_info(proto_source, "dir") == proto_in_dir,
+             "Please define |proto_in_dir| to allow nested directories.")
+    }
+  }
+
+  # Avoid absolute path because of the assumption that |proto_in_dir| is
+  # relative to the directory of current BUILD.gn file.
+  proto_in_dir = rebase_path(proto_in_dir, ".")
+
+  if (defined(invoker.proto_out_dir)) {
+    proto_out_dir = invoker.proto_out_dir
+  } else {
+    # Absolute path to the directory of current BUILD.gn file excluding "//".
+    proto_out_dir = rebase_path(".", "//")
+    if (proto_in_dir != ".") {
+      proto_out_dir += "/$proto_in_dir"
+    }
+  }
+
+  # We need both absolute path to use in GN statements and a relative one
+  # to pass to external script.
+  if (generate_cc || generate_with_plugin) {
+    cc_out_dir = "$root_gen_dir/" + proto_out_dir
+    rel_cc_out_dir = rebase_path(cc_out_dir, root_build_dir)
+  }
+  if (generate_python) {
+    py_out_dir = "$root_out_dir/pyproto/" + proto_out_dir
+    rel_py_out_dir = rebase_path(py_out_dir, root_build_dir)
+  }
+
+  protos = rebase_path(invoker.sources, proto_in_dir)
+  protogens = []
+
+  # List output files.
+  foreach(proto, protos) {
+    proto_dir = get_path_info(proto, "dir")
+    proto_name = get_path_info(proto, "name")
+    proto_path = proto_dir + "/" + proto_name
+
+    if (generate_cc) {
+      protogens += [
+        "$cc_out_dir/$proto_path.pb.h",
+        "$cc_out_dir/$proto_path.pb.cc",
+      ]
+    }
+    if (generate_python) {
+      protogens += [ "$py_out_dir/${proto_path}_pb2.py" ]
+    }
+    if (generate_with_plugin) {
+      protogens += [
+        "$cc_out_dir/${proto_path}$generator_plugin_suffix.h",
+        "$cc_out_dir/${proto_path}$generator_plugin_suffix.cc",
+      ]
+    }
+  }
+
   action_name = "${target_name}_gen"
   source_set_name = target_name
-  action_foreach(action_name) {
+
+  # Generate protobuf stubs.
+  action(action_name) {
     visibility = [ ":$source_set_name" ]
+    script = "//tools/protoc_wrapper/protoc_wrapper.py"
+    sources = proto_sources
+    outputs = get_path_info(protogens, "abspath")
+    args = protos
 
-    script = "//tools/protoc_wrapper/protoc_wrapper.py"
+    protoc_label = "//third_party/protobuf:protoc($host_toolchain)"
+    protoc_out_dir = get_label_info(protoc_label, "root_out_dir")
+    args += [
+      # Wrapper should never pick a system protoc.
+      # Path should be rebased because |root_build_dir| for current toolchain
+      # may be different from |root_out_dir| of protoc built on host toolchain.
+      "--protoc",
+      "./" + rebase_path(protoc_out_dir, root_build_dir) + "/protoc",
+      "--proto-in-dir",
+      rebase_path(proto_in_dir, root_build_dir),
+    ]
 
-    sources = invoker.sources
-
-    # Compute the output directory, both relative to the source root (for
-    # declaring "outputs") and relative to the build dir (for passing to the
-    # script).
-    if (defined(invoker.proto_out_dir)) {
-      proto_out_dir = invoker.proto_out_dir
-    } else {
-      proto_out_dir = "{{source_root_relative_dir}}"
-    }
-    out_dir = "$root_gen_dir/" + proto_out_dir
-    rel_out_dir = rebase_path(out_dir, root_build_dir)
-
-    outputs = []
-
-    args = []
-    if (defined(invoker.cc_include)) {
+    if (generate_cc) {
       args += [
-        "--include",
-        invoker.cc_include,
-        "--protobuf",
-        "$rel_out_dir/{{source_name_part}}.pb.h",
+        "--cc-out-dir",
+        rel_cc_out_dir,
       ]
+      if (defined(invoker.cc_generator_options)) {
+        args += [
+          "--cc-options",
+          invoker.cc_generator_options,
+        ]
+      }
+      if (defined(invoker.cc_include)) {
+        args += [
+          "--include",
+          invoker.cc_include,
+        ]
+      }
     }
 
-    args += [
-      "--proto-in-dir",
-      "{{source_dir}}",
-      "--proto-in-file",
-      "{{source_file_part}}",
-
-      # TODO(brettw) support system protobuf compiler.
-      "--use-system-protobuf=0",
-    ]
-
-    protoc_label = "//third_party/protobuf:protoc($host_toolchain)"
-    args += [
-      "--",
-
-      # Prepend with "./" so this will never pick up the system one (normally
-      # when not cross-compiling, protoc's output directory will be the same
-      # as the build dir, so the relative location will be empty).
-      "./" +
-          rebase_path(get_label_info(protoc_label, "root_out_dir") + "/protoc",
-                      root_build_dir),
-    ]
-
-    if (!defined(invoker.generate_python) || invoker.generate_python) {
-      py_out_dir = "$root_out_dir/pyproto/" + proto_out_dir
-      rel_py_out_dir = rebase_path(py_out_dir, root_build_dir)
-
-      outputs += [ "$py_out_dir/{{source_name_part}}_pb2.py" ]
+    if (generate_python) {
       args += [
-        "--python_out",
+        "--py-out-dir",
         rel_py_out_dir,
       ]
     }
 
-    if (!defined(invoker.generate_cc) || invoker.generate_cc) {
-      # If passed cc_generator_options should end in a colon, which will
-      # separate it from the directory when we concatenate them. The proto
-      # compiler understands this syntax.
-      if (defined(invoker.cc_generator_options)) {
-        cc_generator_options = invoker.cc_generator_options
-      } else {
-        cc_generator_options = ""
-      }
-      outputs += [
-        "$out_dir/{{source_name_part}}.pb.cc",
-        "$out_dir/{{source_name_part}}.pb.h",
-      ]
-      args += [
-        "--cpp_out",
-        "$cc_generator_options$rel_out_dir",  # Separated by colon.
-      ]
-    }
-
-    if (defined(invoker.generator_plugin_label)) {
-      generator_plugin_label = invoker.generator_plugin_label
-      generator_plugin_suffix = invoker.generator_plugin_suffix
-      if (defined(invoker.generator_plugin_options)) {
-        generator_plugin_options = invoker.generator_plugin_options
-      } else {
-        generator_plugin_options = ""
-      }
-      outputs += [
-        "$out_dir/{{source_name_part}}$generator_plugin_suffix.cc",
-        "$out_dir/{{source_name_part}}$generator_plugin_suffix.h",
-      ]
-
-      # Straightforward way to get the name of executable doesn't work because
-      # root_out_dir and root_build_dir may differ in cross-compilation and
-      # also Windows executables have .exe at the end.
-
-      plugin_host_label = generator_plugin_label + "($host_toolchain)"
-      plugin_path = get_label_info(plugin_host_label, "root_out_dir") + "/" +
-                    get_label_info(plugin_host_label, "name")
-      if (host_os == "win") {
-        plugin_path += ".exe"
-      }
-
-      # Need "./" for script to find plugin binary (working dir is not on PATH).
+    if (generate_with_plugin) {
       args += [
         "--plugin",
-        "protoc-gen-plugin=./" + rebase_path(plugin_path, root_build_dir),
-        "--plugin_out",
-        "$generator_plugin_options$rel_out_dir",  # Separated by colon.
+        plugin_path,
+        "--plugin-out-dir",
+        rel_cc_out_dir,
       ]
+      if (defined(invoker.generator_plugin_options)) {
+        args += [
+          "--plugin-options",
+          invoker.generator_plugin_options,
+        ]
+      }
     }
 
     deps = [
+      # System protoc is not used so it's necessary to build a chromium one.
       protoc_label,
     ]
     if (defined(plugin_host_label)) {
+      # Action depends on generator plugin but for host toolchain only.
       deps += [ plugin_host_label ]
     }
-
-    # The deps may have steps that have to run before running protobuf.
     if (defined(invoker.deps)) {
+      # The deps may have steps that have to run before running protoc.
       deps += invoker.deps
     }
   }
 
+  # Option to disable building a library in component build.
   if (defined(invoker.component_build_force_source_set) &&
       invoker.component_build_force_source_set &&
       is_component_build) {
     link_target_type = "source_set"
   } else {
     link_target_type = "static_library"
   }
+
+  # Build generated protobuf stubs as libary or source set.
   target(link_target_type, target_name) {
     forward_variables_from(invoker,
                            [
                              "visibility",
                              "defines",
                            ])
 
     sources = get_target_outputs(":$action_name")
 
     if (defined(invoker.extra_configs)) {
       configs += invoker.extra_configs
     }
 
     public_configs = [ "//third_party/protobuf:using_proto" ]
 
-    # If using built-in cc generator the resulting headers reference headers
-    # within protobuf_lite, hence dependencies require those headers too.
-    # In case of generator plugin such issues should be resolved by invoker.
-    if (!defined(invoker.generate_cc) || invoker.generate_cc) {
+    include_dirs = []
+    if (generate_cc) {
+      include_dirs += [ cc_out_dir ]

[brettw, 2016/08/16 22:08:10]

Does this include directory need to be applied to targets that depend on this
also (that include these headers). I don't see where this happens if you do
indeed need this.

[kraynov, 2016/08/17 00:40:34]

Thank you! This case now fortified by unit test.

+
+      # If using built-in cc generator, the resulting headers reference headers
+      # within protobuf_lite. Hence, dependencies require those headers too.
+      # If using generator plugin, extra deps should be resolved by the invoker.
       public_deps = [
         "//third_party/protobuf:protobuf_lite",
       ]
     }
+    if (generate_with_plugin) {
+      include_dirs += [ cc_out_dir ]
+    }
+
     deps = [
       ":$action_name",
     ]
 
     # This will link any libraries in the deps (the use of invoker.deps in the
     # action won't link it).
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
   }
 }