status_payload_printer.h

// Copyright 2019 The Abseil Authors.
//
// 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.
#ifndef ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_
#define ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_

#include <string>

#include "absl/base/nullability.h"
#include "absl/strings/cord.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace status_internal {

// By default, `Status::ToString` and `operator<<(Status)` print a payload by
// dumping the type URL and the raw bytes. To help debugging, we provide an
// extension point, which is a global printer function that can be set by users
// to specify how to print payloads. The function takes the type URL and the
// payload as input, and should return a valid human-readable string on success
// or `absl::nullopt` on failure (in which case it falls back to the default
// approach of printing the raw bytes).
// NOTE: This is an internal API and the design is subject to change in the
// future in a non-backward-compatible way. Since it's only meant for debugging
// purpose, you should not rely on it in any critical logic.
using StatusPayloadPrinter = absl::Nullable<absl::optional<std::string> (*)(
    absl::string_view, const absl::Cord&)>;

// Sets the global payload printer. Only one printer should be set per process.
// If multiple printers are set, it's undefined which one will be used.
void SetStatusPayloadPrinter(StatusPayloadPrinter);

// Returns the global payload printer if previously set, otherwise `nullptr`.
StatusPayloadPrinter GetStatusPayloadPrinter();

}  // namespace status_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_