chore: migrate common libraries to std::optional (googleapis#16254)

Author: colinmoy

google/cloud/BUILD.bazel

@@ -77,7 +77,6 @@ cc_library(
         "@abseil-cpp//absl/strings",
         "@abseil-cpp//absl/strings:str_format",
         "@abseil-cpp//absl/time",
-        "@abseil-cpp//absl/types:optional",
         "@abseil-cpp//absl/types:span",
         "@abseil-cpp//absl/types:variant",
         "@opentelemetry-cpp//api",

google/cloud/async_streaming_read_write_rpc.h

@@ -19,8 +19,8 @@
 #include "google/cloud/rpc_metadata.h"
 #include "google/cloud/status.h"
 #include "google/cloud/version.h"
-#include "absl/types/optional.h"
 #include <grpcpp/support/async_stream.h>
+#include <optional>
 
 namespace google {
 namespace cloud {
@@ -77,7 +77,7 @@ class AsyncStreamingReadWriteRpc {
    * other `Write()` calls) complete and then call `Finish()` to find the status
    * of the streaming RPC.
    */
-  virtual future<absl::optional<Response>> Read() = 0;
+  virtual future<std::optional<Response>> Read() = 0;
 
   /**
    * Write one request to the streaming RPC.

google/cloud/credentials.cc

@@ -48,13 +48,13 @@ std::shared_ptr<Credentials> MakeImpersonateServiceAccountCredentials(
 std::shared_ptr<Credentials> MakeServiceAccountCredentials(
     std::string json_object, Options opts) {
   return std::make_shared<internal::ServiceAccountConfig>(
-      std::move(json_object), absl::nullopt, std::move(opts));
+      std::move(json_object), std::nullopt, std::move(opts));
 }
 
 std::shared_ptr<Credentials> MakeServiceAccountCredentialsFromFile(
     std::string const& file_path, Options opts) {
   return std::make_shared<internal::ServiceAccountConfig>(
-      absl::nullopt, file_path, std::move(opts));
+      std::nullopt, file_path, std::move(opts));
 }
 
 std::shared_ptr<Credentials> MakeExternalAccountCredentials(

google/cloud/grpc_error_delegate.cc

@@ -14,10 +14,10 @@
 
 #include "google/cloud/grpc_error_delegate.h"
 #include "google/cloud/internal/status_payload_keys.h"
-#include "absl/types/optional.h"
 #include "google/protobuf/any.pb.h"
 #include "google/rpc/error_details.pb.h"
 #include <google/protobuf/text_format.h>
+#include <optional>
 
 namespace google {
 namespace cloud {
@@ -67,7 +67,7 @@ google::cloud::StatusCode MapStatusCode(grpc::StatusCode const& code) {
 }
 
 // Unpacks the ErrorInfo from the Status proto, if one exists.
-absl::optional<google::rpc::ErrorInfo> GetErrorInfoProto(
+std::optional<google::rpc::ErrorInfo> GetErrorInfoProto(
     google::rpc::Status const& proto) {
   // While in theory there _could_ be multiple ErrorInfo protos in this
   // repeated field, we're told that there will be at most one, and our
@@ -76,7 +76,7 @@ absl::optional<google::rpc::ErrorInfo> GetErrorInfoProto(
   for (google::protobuf::Any const& any : proto.details()) {
     if (any.UnpackTo(&error_info)) return error_info;
   }
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 ErrorInfo GetErrorInfo(google::rpc::Status const& status) {
@@ -88,7 +88,7 @@ ErrorInfo GetErrorInfo(google::rpc::Status const& status) {
 }
 
 // Unpacks the RetryInfo from the Status proto, if one exists.
-absl::optional<internal::RetryInfo> GetRetryInfo(
+std::optional<internal::RetryInfo> GetRetryInfo(
     google::rpc::Status const& proto) {
   // While in theory there _could_ be multiple RetryInfo protos in this
   // repeated field, we're told that there will be at most one, and our
@@ -101,7 +101,7 @@ absl::optional<internal::RetryInfo> GetRetryInfo(
       return internal::RetryInfo(d);
     }
   }
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 }  // namespace

google/cloud/grpc_error_delegate_test.cc

@@ -133,7 +133,7 @@ TEST(MakeStatusFromRpcError, AllCodesWithPayload) {
     EXPECT_EQ(expected, actual);
     EXPECT_EQ(message, actual.message());
     EXPECT_EQ(ErrorInfo{}, actual.error_info());
-    EXPECT_EQ(absl::nullopt, internal::GetRetryInfo(actual));
+    EXPECT_EQ(std::nullopt, internal::GetRetryInfo(actual));
 
     // Make sure the actual payload is what we expect.
     auto actual_payload = google::cloud::internal::GetPayload(

google/cloud/grpc_options.cc

@@ -118,30 +118,30 @@ grpc::ChannelArguments MakeChannelArguments(Options const& opts) {
   return channel_arguments;
 }
 
-absl::optional<int> GetIntChannelArgument(grpc::ChannelArguments const& args,
-                                          std::string const& key) {
+std::optional<int> GetIntChannelArgument(grpc::ChannelArguments const& args,
+                                         std::string const& key) {
   auto c_args = args.c_channel_args();
   // Just do a linear search for the key; the data structure is not organized
   // in any other useful way.
   for (auto const* a = c_args.args; a != c_args.args + c_args.num_args; ++a) {
     if (key != a->key) continue;
-    if (a->type != GRPC_ARG_INTEGER) return absl::nullopt;
+    if (a->type != GRPC_ARG_INTEGER) return std::nullopt;
     return a->value.integer;
   }
-  return absl::nullopt;
+  return std::nullopt;
 }
 
-absl::optional<std::string> GetStringChannelArgument(
+std::optional<std::string> GetStringChannelArgument(
     grpc::ChannelArguments const& args, std::string const& key) {
   auto c_args = args.c_channel_args();
   // Just do a linear search for the key; the data structure is not organized
   // in any other useful way.
   for (auto const* a = c_args.args; a != c_args.args + c_args.num_args; ++a) {
     if (key != a->key) continue;
-    if (a->type != GRPC_ARG_STRING) return absl::nullopt;
+    if (a->type != GRPC_ARG_STRING) return std::nullopt;
     return a->value.string;
   }
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 BackgroundThreadsFactory MakeBackgroundThreadsFactory(Options const& opts) {

google/cloud/grpc_options.h

@@ -258,11 +258,11 @@ std::string MakeGrpcHttpProxy(ProxyConfig const& config);
 grpc::ChannelArguments MakeChannelArguments(Options const& opts);
 
 /// Helper function to extract the first instance of an integer channel argument
-absl::optional<int> GetIntChannelArgument(grpc::ChannelArguments const& args,
-                                          std::string const& key);
+std::optional<int> GetIntChannelArgument(grpc::ChannelArguments const& args,
+                                         std::string const& key);
 
 /// Helper function to extract the first instance of a string channel argument
-absl::optional<std::string> GetStringChannelArgument(
+std::optional<std::string> GetStringChannelArgument(
     grpc::ChannelArguments const& args, std::string const& key);
 
 /**

google/cloud/iam_updater.h

@@ -16,9 +16,9 @@
 #define GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_IAM_UPDATER_H
 
 #include "google/cloud/version.h"
-#include "absl/types/optional.h"
 #include "google/iam/v1/policy.pb.h"
 #include <functional>
+#include <optional>
 
 namespace google {
 namespace cloud {
@@ -38,7 +38,7 @@ GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN
  * has been an intermediate update), this update is dropped and a new cycle is
  * initiated. In case (2) the existing policy is overwritten blindly.
  */
-using IamUpdater = std::function<absl::optional<google::iam::v1::Policy>(
+using IamUpdater = std::function<std::optional<google::iam::v1::Policy>(
     google::iam::v1::Policy)>;
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/internal/async_read_write_stream_auth.h

@@ -55,7 +55,7 @@ class AsyncStreamingReadWriteRpcAuth
         });
   }
 
-  future<absl::optional<Response>> Read() override {
+  future<std::optional<Response>> Read() override {
     std::lock_guard<std::mutex> g{state_->mu};
     return state_->stream->Read();
   }

google/cloud/internal/async_read_write_stream_auth_test.cc

@@ -57,7 +57,7 @@ TEST(AsyncStreamReadWriteAuth, Start) {
           return make_ready_future(true);
         });
     EXPECT_CALL(*mock, Read).WillOnce([] {
-      return make_ready_future(absl::make_optional(FakeResponse{"k0", "v0"}));
+      return make_ready_future(std::make_optional(FakeResponse{"k0", "v0"}));
     });
     EXPECT_CALL(*mock, WritesDone).WillOnce([] {
       return make_ready_future(true);