changes for picking up well known protos

Add dependency and protoc argument for picking up well known protos
from the //third_party/protobuf repo

bazel/cc_grpc_library.bzl

@@ -2,7 +2,7 @@
 
 load("//:bazel/generate_cc.bzl", "generate_cc")
 
-def cc_grpc_library(name, srcs, deps, proto_only, use_external = False, **kwargs):
+def cc_grpc_library(name, srcs, deps, proto_only, well_known_protos, use_external = False, **kwargs):
   """Generates C++ grpc classes from a .proto file.
 
   Assumes the generated classes will be used in cc_api_version = 2.
@@ -12,6 +12,9 @@ def cc_grpc_library(name, srcs, deps, proto_only, use_external = False, **kwargs
       srcs: a single proto_library, which wraps the .proto files with services.
       deps: a list of C++ proto_library (or cc_proto_library) which provides
         the compiled code of any message that the services depend on.
+      well_known_protos: The target from protobuf library that exports well
+        known protos. Currently it will only work if the value is
+        "@submodule_protobuf//:well_known_protos"
       use_external: When True the grpc deps are prefixed with //external. This
         allows grpc to be used as a dependency in other bazel projects.
       **kwargs: rest of arguments, e.g., compatible_with and visibility.
@@ -35,6 +38,7 @@ def cc_grpc_library(name, srcs, deps, proto_only, use_external = False, **kwargs
   generate_cc(
       name = codegen_target,
       srcs = [proto_target],
+      well_known_protos = well_known_protos,
       **kwargs
   )
 
@@ -49,6 +53,7 @@ def cc_grpc_library(name, srcs, deps, proto_only, use_external = False, **kwargs
         name = codegen_grpc_target,
         srcs = [proto_target],
         plugin = plugin,
+        well_known_protos = well_known_protos,
         **kwargs
     )
 

bazel/generate_cc.bzl

@@ -31,8 +31,20 @@ def generate_cc_impl(ctx):
   arguments += ["-I{0}={0}".format(include.path) for include in includes]
   arguments += [proto.path for proto in protos]
 
+  # create a list of well known proto files if the argument is non-None
+  well_known_proto_files = []
+  if ctx.attr.well_known_protos:
+    f = ctx.attr.well_known_protos.files.to_list()[0].dirname
+    if f != "external/submodule_protobuf/src/google/protobuf":
+      print("Error: Only @submodule_protobuf//:well_known_protos is supported")
+    else:
+      # f points to "external/submodule_protobuf/src/google/protobuf"
+      # add -I argument to protoc so it knows where to look for the proto files.
+      arguments += ["-I{0}".format(f + "/../..")]
+      well_known_proto_files = [f for f in ctx.attr.well_known_protos.files]
+
   ctx.action(
-      inputs = protos + includes + additional_input,
+      inputs = protos + includes + additional_input + well_known_proto_files,
       outputs = out_files,
       executable = ctx.executable._protoc,
       arguments = arguments,
@@ -56,6 +68,9 @@ generate_cc = rule(
             mandatory = False,
             allow_empty = True,
         ),
+        "well_known_protos" : attr.label(
+            mandatory = False,
+        ),
         "_protoc": attr.label(
             default = Label("//external:protocol_compiler"),
             executable = True,

bazel/grpc_build_system.bzl

@@ -58,11 +58,13 @@ def grpc_proto_plugin(name, srcs = [], deps = []):
 
 load("//:bazel/cc_grpc_library.bzl", "cc_grpc_library")
 
-def grpc_proto_library(name, srcs = [], deps = [], well_known_deps = [], has_services = True, use_external = False):
+def grpc_proto_library(name, srcs = [], deps = [], well_known_protos = None,
+                       has_services = True, use_external = False):
   cc_grpc_library(
     name = name,
     srcs = srcs,
     deps = deps,
+    well_known_protos = well_known_protos,
     proto_only = not has_services,
     use_external = use_external,
   )