address comments

Author: cuiy0006

.bazelrc

@@ -55,6 +55,8 @@ common:macos --repo_env=BAZEL_NO_APPLE_CPP_TOOLCHAIN=1
 test --test_env=GTEST_SHUFFLE --test_env=GTEST_RANDOM_SEED
 
 # By default, build the library with OpenTelemetry
+# Enable the config when the bool flag is visible.
+# https://github.com/googleapis/google-cloud-cpp-bigquery/issues/98
 # build --@com_google_googleapis_google_cloud_cpp//:enable_opentelemetry
 
 # Don't show warnings when building external dependencies. This still shows

google/cloud/bigquery_unified/BUILD.bazel

@@ -61,7 +61,7 @@ cc_library(
     srcs = google_cloud_cpp_bigquery_bigquery_unified_srcs,
     hdrs = google_cloud_cpp_bigquery_bigquery_unified_hdrs,
     # Enable the config when the bool flag is visible.
-    # https://github.com/googleapis/google-cloud-cpp/pull/14961
+    # https://github.com/googleapis/google-cloud-cpp-bigquery/issues/98
     # defines = select({
     #     ":enable_opentelemetry": [
     #         # Enable OpenTelemetry features in google-cloud-cpp

google/cloud/bigquery_unified/CMakeLists.txt

@@ -190,9 +190,11 @@ if (GOOGLE_CLOUD_CPP_BIGQUERY_ENABLE_OPENTELEMETRY)
     else ()
         message(
             FATAL_ERROR
-                "OpenTelemetry is not enabled in the package "
-                "google-cloud-cpp, the target "
-                "google-cloud-cpp::opentelemetry is not available.")
+                "Instrumentation with OpenTelemetry was requested "
+                "for google-cloud-cpp-bigquery, but it was not enabled "
+                "in google-cloud-cpp. Please build and install "
+                "google-cloud-cpp with GOOGLE_CLOUD_CPP_ENABLE=opentelemetry "
+                "if you want to use this feature.")
     endif ()
 endif ()
 
@@ -255,6 +257,7 @@ function (bigquery_unified_client_define_tests)
     set(bigquery_unified_client_unit_tests
         # cmake-format: sort
         client_test.cc
+        connection_test.cc
         internal/connection_impl_test.cc
         internal/default_options_test.cc
         internal/tracing_connection_test.cc

google/cloud/bigquery_unified/bigquery_unified_client_unit_tests.bzl

@@ -18,6 +18,7 @@
 
 bigquery_unified_client_unit_tests = [
     "client_test.cc",
+    "connection_test.cc",
     "internal/connection_impl_test.cc",
     "internal/default_options_test.cc",
     "internal/tracing_connection_test.cc",

google/cloud/bigquery_unified/connection_test.cc

@@ -0,0 +1,68 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// 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.
+
+#include "google/cloud/bigquery_unified/version.h"
+#include "google/cloud/bigquery_unified/connection.h"
+#include "google/cloud/bigquery_unified/testing_util/opentelemetry_matchers.h"
+
+namespace google::cloud::bigquery_unified {
+GOOGLE_CLOUD_CPP_BIGQUERY_INLINE_NAMESPACE_BEGIN
+namespace {
+
+#ifdef GOOGLE_CLOUD_CPP_BIGQUERY_HAVE_OPENTELEMETRY
+using ::google::cloud::bigquery_unified::testing_util::DisableTracing;
+using ::google::cloud::bigquery_unified::testing_util::EnableTracing;
+using ::google::cloud::bigquery_unified::testing_util::SpanNamed;
+using ::testing::Not;
+using ::testing::Contains;
+
+TEST(BigQueryUnifiedConnectionTest, TracingEnabled) {
+  auto span_catcher = testing_util::InstallSpanCatcher();
+
+  auto options = EnableTracing(Options{});
+  auto conn = MakeConnection(std::move(options));
+  google::cloud::internal::OptionsSpan span(
+      google::cloud::internal::MergeOptions(Options{}, conn->options()));
+  // Make a call, which should fail fast. The error itself is not important.
+  google::cloud::bigquery::v2::GetJobRequest request;
+  (void)conn->GetJob(request, Options{});
+
+  auto spans = span_catcher->GetSpans();
+  EXPECT_THAT(
+      spans,
+      Contains(SpanNamed("bigquery_unified::Connection::GetJob")));
+}
+
+TEST(BigQueryUnifiedConnectionTest, TracingDisabled) {
+  auto span_catcher = testing_util::InstallSpanCatcher();
+
+  auto options = DisableTracing(Options{});
+  auto conn = MakeConnection(std::move(options));
+  google::cloud::internal::OptionsSpan span(
+      google::cloud::internal::MergeOptions(Options{}, conn->options()));
+  // Make a call, which should fail fast. The error itself is not important.
+  google::cloud::bigquery::v2::GetJobRequest request;
+  (void)conn->GetJob(request, Options{});
+
+  auto spans = span_catcher->GetSpans();
+  EXPECT_THAT(spans,
+              Not(Contains(SpanNamed(
+                  "bigquery_unified::Connection::GetJob"))));
+}
+
+#endif  // GOOGLE_CLOUD_CPP_BIGQUERY_HAVE_OPENTELEMETRY
+
+}  // namespace
+GOOGLE_CLOUD_CPP_BIGQUERY_INLINE_NAMESPACE_END
+}  // namespace google::cloud::bigquery_unified

google/cloud/bigquery_unified/testing_util/BUILD.bazel

@@ -43,7 +43,7 @@ cc_library(
         "@google_cloud_cpp//:common",
     ],
     # Enable the config when the bool flag is visible.
-    # https://github.com/googleapis/google-cloud-cpp/pull/14961
+    # https://github.com/googleapis/google-cloud-cpp-bigquery/issues/98
     # + select({
     #     ":enable_opentelemetry": [
     #         "@io_opentelemetry_cpp//exporters/memory:in_memory_span_exporter",