chore: migrate from deprecated absl types to std equivalents (#16400)

Author: scotthart

MODULE.bazel

@@ -23,7 +23,7 @@ module(
 bazel_dep(name = "platforms", version = "1.1.0")
 bazel_dep(name = "bazel_skylib", version = "1.9.2")
 bazel_dep(name = "rules_cc", version = "0.2.17")
-bazel_dep(name = "abseil-cpp", version = "20250814.2")
+bazel_dep(name = "abseil-cpp", version = "20260526.0")
 
 # For backwards compatibility with WORKSPACE.
 # The name "com_google_protobuf" is internally used by @bazel_tools,

examples/api_key.cc

@@ -33,6 +33,7 @@
 #include "absl/strings/str_split.h"
 #include <chrono>
 #include <iostream>
+#include <optional>
 #include <string>
 #include <thread>
 #include <vector>
@@ -147,7 +148,7 @@ void AutoRun(std::vector<std::string> const& argv) {
     // When we authenticate with an API key, we do not have (or need)
     // credentials. Using a quota project requires credentials, so disable it.
     google::cloud::testing_util::ScopedEnvironment overlay(
-        "GOOGLE_CLOUD_CPP_USER_PROJECT", absl::nullopt);
+        "GOOGLE_CLOUD_CPP_USER_PROJECT", std::nullopt);
 
     try {
       AuthenticateWithApiKey({project_id, key.key_string()});

generator/integration_tests/golden/v1/golden_kitchen_sink_connection.cc

@@ -84,7 +84,7 @@ StreamRange<google::test::admin::database::v1::Response> GoldenKitchenSinkConnec
     google::test::admin::database::v1::Request const&) {
   return google::cloud::internal::MakeStreamRange<
       google::test::admin::database::v1::Response>(
-      []() -> absl::variant<Status,
+      []() -> std::variant<Status,
       google::test::admin::database::v1::Response>{
         return Status(StatusCode::kUnimplemented, "not implemented");}
       );

generator/integration_tests/golden/v1/internal/golden_kitchen_sink_connection_impl.cc

@@ -184,7 +184,7 @@ GoldenKitchenSinkConnectionImpl::StreamingRead(google::test::admin::database::v1
           GoldenKitchenSinkStreamingReadStreamingUpdater, request);
   return internal::MakeStreamRange<google::test::admin::database::v1::Response>(
       [resumable = std::move(resumable)]()
-          -> absl::variant<
+          -> std::variant<
               Status,
               google::test::admin::database::v1::Response> {
         google::test::admin::database::v1::Response response;

generator/integration_tests/golden/v1/internal/golden_kitchen_sink_metadata_decorator.cc

@@ -175,7 +175,7 @@ GoldenKitchenSinkMetadata::ExplicitRouting1(
       {[](google::test::admin::database::v1::ExplicitRoutingRequest const& request) -> std::string const& {
         return request.app_profile_id();
       },
-      absl::nullopt},
+      std::nullopt},
       {[](google::test::admin::database::v1::ExplicitRoutingRequest const& request) -> std::string const& {
         return request.table_name();
       },

generator/integration_tests/golden/v1/internal/golden_kitchen_sink_rest_metadata_decorator.cc

@@ -120,7 +120,7 @@ GoldenKitchenSinkRestMetadata::ExplicitRouting1(
       {[](google::test::admin::database::v1::ExplicitRoutingRequest const& request) -> std::string const& {
         return request.app_profile_id();
       },
-      absl::nullopt},
+      std::nullopt},
       {[](google::test::admin::database::v1::ExplicitRoutingRequest const& request) -> std::string const& {
         return request.table_name();
       },

generator/integration_tests/tests/golden_kitchen_sink_client_test.cc

@@ -239,7 +239,7 @@ TEST(GoldenKitchenSinkClientTest, StreamingRead) {
                     Contains("test-only/1.0"));
         EXPECT_THAT(request.stream(), "test-only-stream-name");
         return google::cloud::internal::MakeStreamRange<Response>(
-            []() -> absl::variant<Status, Response> {
+            []() -> std::variant<Status, Response> {
               return Status(StatusCode::kPermissionDenied, "uh-oh");
             });
       });

generator/internal/connection_generator.cc

@@ -460,7 +460,7 @@ std::unique_ptr<::google::cloud::AsyncStreamingReadWriteRpc<
     "    $request_type$ const&) {\n"
     "  return google::cloud::internal::MakeStreamRange<\n"
     "      $response_type$>(\n"
-    "      []() -> absl::variant<Status,\n"
+    "      []() -> std::variant<Status,\n"
     "      $response_type$>{\n"
     "        return Status(StatusCode::kUnimplemented, \"not implemented\");}\n"
     "      );\n"

generator/internal/connection_impl_generator.cc

@@ -363,7 +363,7 @@ StreamRange<$response_type$>
           $service_name$$method_name$StreamingUpdater, request);
   return internal::MakeStreamRange<$response_type$>(
       [resumable = std::move(resumable)]()
-          -> absl::variant<
+          -> std::variant<
               Status,
               $response_type$> {
         $response_type$ response;

generator/internal/descriptor_utils.cc

@@ -34,7 +34,6 @@
 #include "absl/strings/str_replace.h"
 #include "absl/strings/str_split.h"
 #include "absl/strings/strip.h"
-#include "absl/types/variant.h"
 #include "google/api/annotations.pb.h"
 #include "google/api/http.pb.h"
 #include "google/api/routing.pb.h"