add golang bazel build support (#132)

src/BUILD.bazel

@@ -10,4 +10,9 @@
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
-# limitations under the License.
+# limitations under the License.
+
+package(default_visibility = ["//visibility:public"])
+
+load("@io_bazel_rules_go//go:def.bzl", "go_prefix")
+go_prefix("github.com/census-instrumentation/opencensus-proto")

src/WORKSPACE

@@ -54,3 +54,37 @@ http_archive(
     strip_prefix = "protobuf-3.5.1",
     urls = ["https://github.com/google/protobuf/archive/v3.5.1.tar.gz"],
 )
+
+# go rules related
+git_repository(
+    name = "io_bazel_rules_go",
+    remote = "https://github.com/bazelbuild/rules_go.git",
+    # we need rules_go of tag 0.12.0
+    # which includes golang protobuf that supports "paths=source_relative"
+    # the "paths=source_relative" option for protoc-gen-go makes bazel works as expect
+    # when go_package was declared in proto files
+    # see https://github.com/bazelbuild/rules_go/blob/release-0.12/go/private/repositories.bzl#L75
+    # for the included golang protobuf version and
+    # see https://github.com/golang/protobuf/pull/544 for "paths=source_relative" usage
+    tag = "0.12.0",
+)
+
+load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains")
+go_rules_dependencies()
+go_register_toolchains()
+
+# golang protobuf rules related
+git_repository(
+    name = "org_pubref_rules_protobuf",
+    commit = "5cae42382b620aa1e347ecf30b3e92fd0d97998c", # Jun 23, 2018
+    remote = "https://github.com/pubref/rules_protobuf.git",
+)
+
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_repositories")
+go_proto_repositories(
+  excludes = [
+        # we have specified protobuf above
+        # so ignore it in case version collision
+        "com_google_protobuf",
+  ],
+)

src/opencensus/proto/agent/common/v1/BUILD.bazel

@@ -14,6 +14,8 @@
 
 package(default_visibility = ["//visibility:public"])
 
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_library")
+
 proto_library(
     name = "common_proto",
     srcs = ["common.proto"],
@@ -21,3 +23,21 @@ proto_library(
         "@com_google_protobuf//:timestamp_proto",
     ],
 )
+
+go_proto_library(
+    name = "common_proto_go",
+    protos = ["common.proto"],
+    imports = [
+        "external/com_google_protobuf/src",
+    ],
+    inputs = [
+        "@com_google_protobuf//:well_known_protos",
+    ],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+    deps = [
+        "@com_github_golang_protobuf//ptypes/timestamp:go_default_library",
+    ],
+)

src/opencensus/proto/agent/trace/v1/BUILD.bazel

@@ -15,6 +15,7 @@
 package(default_visibility = ["//visibility:public"])
 
 load("@grpc_java//:java_grpc_library.bzl", "java_grpc_library")
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_library")
 
 proto_library(
     name = "trace_service_proto",
@@ -52,3 +53,20 @@ java_grpc_library(
 #    deps = [
 #    ],
 #)
+
+go_proto_library(
+    name = "trace_service_proto_go",
+    protos = ["trace_service.proto"],
+    imports = [
+        "external/com_google_protobuf/src",
+    ],
+    proto_deps = [
+        "//opencensus/proto/agent/common/v1:common_proto_go",
+        "//opencensus/proto/trace/v1:trace_proto_go",
+        "//opencensus/proto/trace/v1:trace_config_proto_go",
+    ],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+)

src/opencensus/proto/metrics/v1/BUILD.bazel

@@ -14,6 +14,8 @@
 
 package(default_visibility = ["//visibility:public"])
 
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_library")
+
 proto_library(
     name = "metrics_proto",
     srcs = ["metrics.proto"],
@@ -32,3 +34,22 @@ java_proto_library(
     name = "metrics_proto_java",
     deps = [":metrics_proto"],
 )
+
+go_proto_library(
+    name = "metrics_proto_go",
+    protos = ["metrics.proto"],
+    imports = [
+        "external/com_google_protobuf/src",
+    ],
+    inputs = [
+        "@com_google_protobuf//:well_known_protos",
+    ],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+    deps = [
+        "@com_github_golang_protobuf//ptypes/timestamp:go_default_library",
+        "@com_github_golang_protobuf//ptypes/wrappers:go_default_library",
+    ],
+)

src/opencensus/proto/stats/v1/BUILD.bazel

@@ -14,6 +14,8 @@
 
 package(default_visibility = ["//visibility:public"])
 
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_library")
+
 proto_library(
     name = "stats_proto",
     srcs = ["stats.proto"],
@@ -32,3 +34,21 @@ java_proto_library(
     name = "stats_proto_java",
     deps = [":stats_proto"],
 )
+
+go_proto_library(
+    name = "stats_proto_go",
+    protos = ["stats.proto"],
+    imports = [
+        "external/com_google_protobuf/src",
+    ],
+    inputs = [
+        "@com_google_protobuf//:well_known_protos",
+    ],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+    deps = [
+        "@com_github_golang_protobuf//ptypes/timestamp:go_default_library",
+    ],
+)

src/opencensus/proto/trace/v1/BUILD.bazel

@@ -14,6 +14,8 @@
 
 package(default_visibility = ["//visibility:public"])
 
+load("@org_pubref_rules_protobuf//go:rules.bzl", "go_proto_library")
+
 proto_library(
     name = "trace_proto",
     srcs = ["trace.proto"],
@@ -47,3 +49,31 @@ java_proto_library(
     name = "trace_config_proto_java",
     deps = [":trace_config_proto"],
 )
+
+go_proto_library(
+    name = "trace_proto_go",
+    protos = ["trace.proto"],
+    imports = [
+        "external/com_google_protobuf/src",
+    ],
+    inputs = [
+        "@com_google_protobuf//:well_known_protos",
+    ],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+    deps = [
+        "@com_github_golang_protobuf//ptypes/timestamp:go_default_library",
+        "@com_github_golang_protobuf//ptypes/wrappers:go_default_library",
+    ],
+)
+
+go_proto_library(
+    name = "trace_config_proto_go",
+    protos = ["trace_config.proto"],
+    pb_options = [
+       # omit the go_package declared in proto files to make bazel works as expect
+       "paths=source_relative",
+    ],
+)