absl/flags/usage_config.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.
//
// -----------------------------------------------------------------------------
// File: usage_config.h
// -----------------------------------------------------------------------------
//
// This file defines the main usage reporting configuration interfaces and
// documents Abseil's supported built-in usage flags. If these flags are found
// when parsing a command-line, Abseil will exit the program and display
// appropriate help messages.
#ifndef ABSL_FLAGS_USAGE_CONFIG_H_
#define ABSL_FLAGS_USAGE_CONFIG_H_

#include <functional>
#include <string>

#include "absl/base/config.h"
#include "absl/strings/string_view.h"

// -----------------------------------------------------------------------------
// Built-in Usage Flags
// -----------------------------------------------------------------------------
//
// Abseil supports the following built-in usage flags. When passed, these flags
// exit the program and :
//
// * --help
//     Shows help on important flags for this binary
// * --helpfull
//     Shows help on all flags
// * --helpshort
//     Shows help on only the main module for this program
// * --helppackage
//     Shows help on all modules in the main package
// * --version
//     Shows the version and build info for this binary and exits
// * --only_check_args
//     Exits after checking all flags
// * --helpon
//     Shows help on the modules named by this flag value
// * --helpmatch
//     Shows help on modules whose name contains the specified substring

namespace absl {
ABSL_NAMESPACE_BEGIN

namespace flags_internal {
using FlagKindFilter = std::function<bool (absl::string_view)>;
}  // namespace flags_internal

// FlagsUsageConfig
//
// This structure contains the collection of callbacks for changing the behavior
// of the usage reporting routines in Abseil Flags.
struct FlagsUsageConfig {
  // Returns true if flags defined in the given source code file should be
  // reported with --helpshort flag. For example, if the file
  // "path/to/my/code.cc" defines the flag "--my_flag", and
  // contains_helpshort_flags("path/to/my/code.cc") returns true, invoking the
  // program with --helpshort will include information about --my_flag in the
  // program output.
  flags_internal::FlagKindFilter contains_helpshort_flags;

  // Returns true if flags defined in the filename should be reported with
  // --help flag. For example, if the file
  // "path/to/my/code.cc" defines the flag "--my_flag", and
  // contains_help_flags("path/to/my/code.cc") returns true, invoking the
  // program with --help will include information about --my_flag in the
  // program output.
  flags_internal::FlagKindFilter contains_help_flags;

  // Returns true if flags defined in the filename should be reported with
  // --helppackage flag. For example, if the file
  // "path/to/my/code.cc" defines the flag "--my_flag", and
  // contains_helppackage_flags("path/to/my/code.cc") returns true, invoking the
  // program with --helppackage will include information about --my_flag in the
  // program output.
  flags_internal::FlagKindFilter contains_helppackage_flags;

  // Generates string containing program version. This is the string reported
  // when user specifies --version in a command line.
  std::function<std::string()> version_string;

  // Normalizes the filename specific to the build system/filesystem used. This
  // routine is used when we report the information about the flag definition
  // location. For instance, if your build resides at some location you do not
  // want to expose in the usage output, you can trim it to show only relevant
  // part.
  // For example:
  //   normalize_filename("/my_company/some_long_path/src/project/file.cc")
  // might produce
  //   "project/file.cc".
  std::function<std::string(absl::string_view)> normalize_filename;
};

// SetFlagsUsageConfig()
//
// Sets the usage reporting configuration callbacks. If any of the callbacks are
// not set in usage_config instance, then the default value of the callback is
// used.
void SetFlagsUsageConfig(FlagsUsageConfig usage_config);

namespace flags_internal {

FlagsUsageConfig GetUsageConfig();

void ReportUsageError(absl::string_view msg, bool is_fatal);

}  // namespace flags_internal
ABSL_NAMESPACE_END
}  // namespace absl

extern "C" {

// Additional report of fatal usage error message before we std::exit. Error is
// fatal if is_fatal argument to ReportUsageError is true.
void ABSL_INTERNAL_C_SYMBOL(AbslInternalReportFatalUsageError)(
    absl::string_view);

}  // extern "C"

#endif  // ABSL_FLAGS_USAGE_CONFIG_H_