Export of internal Abseil changes

--
30e5e00a54cabc50118a3e1055826ea02a0d32e4 by Gennadiy Rozental <rogeeff@google.com>:

Move flag help into flag_cold section.

To facilitate this we set flag help not in a constructor, but during flag registration. This allows us to place flag name as static variable inside non constexpr lambda and invoke it immediately in FlagRegistrar argument location.

PiperOrigin-RevId: 312432625

--
efd91b05152b68df648cff5ba38e9669a817c12f by Gennadiy Rozental <rogeeff@google.com>:

Make CommandLineFlag public.

PiperOrigin-RevId: 312404666

--
dc7f5fb73487766fa8a76d6b97d28116e5334445 by Mark Barolak <mbar@google.com>:

Internal change.

PiperOrigin-RevId: 312297164
GitOrigin-RevId: 30e5e00a54cabc50118a3e1055826ea02a0d32e4
Change-Id: Ic46ab011bb804645264572caddff0becba5f9170

13 files changed, 53 insertions, 423 deletions

diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/internal/commandlineflag.cc
deleted file mode 100644
index 84112437..00000000
--- a/absl/flags/internal/commandlineflag.cc
+++ /dev/null
@@ -1,34 +0,0 @@
-//
-// Copyright 2020 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.
-
-#include "absl/flags/internal/commandlineflag.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace flags_internal {
-
-FlagStateInterface::~FlagStateInterface() {}
-
-bool CommandLineFlag::IsRetired() const { return false; }
-
-bool CommandLineFlag::ParseFrom(absl::string_view value, std::string* error) {
-  return ParseFrom(value, flags_internal::SET_FLAGS_VALUE,
-                   flags_internal::kProgrammaticChange, error);
-}
-
-}  // namespace flags_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
-
diff --git a/absl/flags/internal/commandlineflag.h b/absl/flags/internal/commandlineflag.h
index fa050209..3c149788 100644
--- a/absl/flags/internal/commandlineflag.h
+++ b/absl/flags/internal/commandlineflag.h
@@ -23,7 +23,6 @@
 #include "absl/base/internal/fast_type_id.h"
 #include "absl/base/macros.h"
 #include "absl/strings/string_view.h"
-#include "absl/types/optional.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -67,117 +66,6 @@ class FlagStateInterface {
   virtual void Restore() const = 0;
 };
 
-// Holds all information for a flag.
-class CommandLineFlag {
- public:
-  constexpr CommandLineFlag() = default;
-
-  // Not copyable/assignable.
-  CommandLineFlag(const CommandLineFlag&) = delete;
-  CommandLineFlag& operator=(const CommandLineFlag&) = delete;
-
-  // Non-polymorphic access methods.
-
-  // Return true iff flag has type T.
-  template <typename T>
-  inline bool IsOfType() const {
-    return TypeId() == base_internal::FastTypeId<T>();
-  }
-
-  // Attempts to retrieve the flag value. Returns value on success,
-  // absl::nullopt otherwise.
-  template <typename T>
-  absl::optional<T> TryGet() const {
-    if (IsRetired() || !IsOfType<T>()) {
-      return absl::nullopt;
-    }
-
-    // Implementation notes:
-    //
-    // We are wrapping a union around the value of `T` to serve three purposes:
-    //
-    //  1. `U.value` has correct size and alignment for a value of type `T`
-    //  2. The `U.value` constructor is not invoked since U's constructor does
-    //     not do it explicitly.
-    //  3. The `U.value` destructor is invoked since U's destructor does it
-    //     explicitly. This makes `U` a kind of RAII wrapper around non default
-    //     constructible value of T, which is destructed when we leave the
-    //     scope. We do need to destroy U.value, which is constructed by
-    //     CommandLineFlag::Read even though we left it in a moved-from state
-    //     after std::move.
-    //
-    // All of this serves to avoid requiring `T` being default constructible.
-    union U {
-      T value;
-      U() {}
-      ~U() { value.~T(); }
-    };
-    U u;
-
-    Read(&u.value);
-    return std::move(u.value);
-  }
-
-  // Polymorphic access methods
-
-  // Returns name of this flag.
-  virtual absl::string_view Name() const = 0;
-  // Returns name of the file where this flag is defined.
-  virtual std::string Filename() const = 0;
-  // Returns help message associated with this flag.
-  virtual std::string Help() const = 0;
-  // Returns true iff this object corresponds to retired flag.
-  virtual bool IsRetired() const;
-  virtual std::string DefaultValue() const = 0;
-  virtual std::string CurrentValue() const = 0;
-
-  // Sets the value of the flag based on specified string `value`. If the flag
-  // was successfully set to new value, it returns true. Otherwise, sets `error`
-  // to indicate the error, leaves the flag unchanged, and returns false.
-  bool ParseFrom(absl::string_view value, std::string* error);
-
- protected:
-  ~CommandLineFlag() = default;
-
- private:
-  friend class PrivateHandleAccessor;
-
-  // Sets the value of the flag based on specified string `value`. If the flag
-  // was successfully set to new value, it returns true. Otherwise, sets `error`
-  // to indicate the error, leaves the flag unchanged, and returns false. There
-  // are three ways to set the flag's value:
-  //  * Update the current flag value
-  //  * Update the flag's default value
-  //  * Update the current flag value if it was never set before
-  // The mode is selected based on `set_mode` parameter.
-  virtual bool ParseFrom(absl::string_view value,
-                         flags_internal::FlagSettingMode set_mode,
-                         flags_internal::ValueSource source,
-                         std::string* error) = 0;
-
-  // Returns id of the flag's value type.
-  virtual FlagFastTypeId TypeId() const = 0;
-
-  // Interface to save flag to some persistent state. Returns current flag state
-  // or nullptr if flag does not support saving and restoring a state.
-  virtual std::unique_ptr<FlagStateInterface> SaveState() = 0;
-
-  // Copy-construct a new value of the flag's type in a memory referenced by
-  // the dst based on the current flag's value.
-  virtual void Read(void* dst) const = 0;
-
-  // To be deleted. Used to return true if flag's current value originated from
-  // command line.
-  virtual bool IsSpecifiedOnCommandLine() const = 0;
-
-  // Validates supplied value usign validator or parseflag routine
-  virtual bool ValidateInputValue(absl::string_view value) const = 0;
-
-  // Checks that flags default value can be converted to string and back to the
-  // flag's value type.
-  virtual void CheckDefaultValueParsingRoundtrip() const = 0;
-};
-
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/commandlineflag_test.cc b/absl/flags/internal/commandlineflag_test.cc
deleted file mode 100644
index 0b5aea37..00000000
--- a/absl/flags/internal/commandlineflag_test.cc
+++ /dev/null
@@ -1,233 +0,0 @@
-//
-//  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.
-
-#include "absl/flags/internal/commandlineflag.h"
-
-#include <memory>
-#include <string>
-
-#include "gtest/gtest.h"
-#include "absl/flags/flag.h"
-#include "absl/flags/internal/private_handle_accessor.h"
-#include "absl/flags/internal/registry.h"
-#include "absl/flags/usage_config.h"
-#include "absl/memory/memory.h"
-#include "absl/strings/match.h"
-#include "absl/strings/str_cat.h"
-#include "absl/strings/string_view.h"
-
-ABSL_FLAG(int, int_flag, 201, "int_flag help");
-ABSL_FLAG(std::string, string_flag, "dflt",
-          absl::StrCat("string_flag", " help"));
-ABSL_RETIRED_FLAG(bool, bool_retired_flag, false, "bool_retired_flag help");
-
-namespace {
-
-namespace flags = absl::flags_internal;
-
-class CommandLineFlagTest : public testing::Test {
- protected:
-  static void SetUpTestSuite() {
-    // Install a function to normalize filenames before this test is run.
-    absl::FlagsUsageConfig default_config;
-    default_config.normalize_filename = &CommandLineFlagTest::NormalizeFileName;
-    absl::SetFlagsUsageConfig(default_config);
-  }
-
-  void SetUp() override { flag_saver_ = absl::make_unique<flags::FlagSaver>(); }
-  void TearDown() override { flag_saver_.reset(); }
-
- private:
-  static std::string NormalizeFileName(absl::string_view fname) {
-#ifdef _WIN32
-    std::string normalized(fname);
-    std::replace(normalized.begin(), normalized.end(), '\\', '/');
-    fname = normalized;
-#endif
-    return std::string(fname);
-  }
-
-  std::unique_ptr<flags::FlagSaver> flag_saver_;
-};
-
-TEST_F(CommandLineFlagTest, TestAttributesAccessMethods) {
-  auto* flag_01 = flags::FindCommandLineFlag("int_flag");
-
-  ASSERT_TRUE(flag_01);
-  EXPECT_EQ(flag_01->Name(), "int_flag");
-  EXPECT_EQ(flag_01->Help(), "int_flag help");
-  EXPECT_TRUE(!flag_01->IsRetired());
-  EXPECT_TRUE(flag_01->IsOfType<int>());
-  EXPECT_TRUE(
-      absl::EndsWith(flag_01->Filename(),
-                     "absl/flags/internal/commandlineflag_test.cc"))
-      << flag_01->Filename();
-
-  auto* flag_02 = flags::FindCommandLineFlag("string_flag");
-
-  ASSERT_TRUE(flag_02);
-  EXPECT_EQ(flag_02->Name(), "string_flag");
-  EXPECT_EQ(flag_02->Help(), "string_flag help");
-  EXPECT_TRUE(!flag_02->IsRetired());
-  EXPECT_TRUE(flag_02->IsOfType<std::string>());
-  EXPECT_TRUE(
-      absl::EndsWith(flag_02->Filename(),
-                     "absl/flags/internal/commandlineflag_test.cc"))
-      << flag_02->Filename();
-
-  auto* flag_03 = flags::FindRetiredFlag("bool_retired_flag");
-
-  ASSERT_TRUE(flag_03);
-  EXPECT_EQ(flag_03->Name(), "bool_retired_flag");
-  EXPECT_EQ(flag_03->Help(), "");
-  EXPECT_TRUE(flag_03->IsRetired());
-  EXPECT_TRUE(flag_03->IsOfType<bool>());
-  EXPECT_EQ(flag_03->Filename(), "RETIRED");
-}
-
-// --------------------------------------------------------------------
-
-TEST_F(CommandLineFlagTest, TestValueAccessMethods) {
-  absl::SetFlag(&FLAGS_int_flag, 301);
-  auto* flag_01 = flags::FindCommandLineFlag("int_flag");
-
-  ASSERT_TRUE(flag_01);
-  EXPECT_EQ(flag_01->CurrentValue(), "301");
-  EXPECT_EQ(flag_01->DefaultValue(), "201");
-
-  absl::SetFlag(&FLAGS_string_flag, "new_str_value");
-  auto* flag_02 = flags::FindCommandLineFlag("string_flag");
-
-  ASSERT_TRUE(flag_02);
-  EXPECT_EQ(flag_02->CurrentValue(), "new_str_value");
-  EXPECT_EQ(flag_02->DefaultValue(), "dflt");
-}
-
-// --------------------------------------------------------------------
-
-TEST_F(CommandLineFlagTest, TestParseFromCurrentValue) {
-  std::string err;
-
-  auto* flag_01 = flags::FindCommandLineFlag("int_flag");
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "11", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 11);
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "-123", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "xyz", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
-  EXPECT_EQ(err, "Illegal value 'xyz' specified for flag 'int_flag'");
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "A1", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
-  EXPECT_EQ(err, "Illegal value 'A1' specified for flag 'int_flag'");
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "0x10", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 16);
-  EXPECT_FALSE(
-      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "011", flags::SET_FLAGS_VALUE, flags::kCommandLine, &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 11);
-  EXPECT_TRUE(flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
-
-  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, &err));
-  EXPECT_EQ(err, "Illegal value '' specified for flag 'int_flag'");
-
-  auto* flag_02 = flags::FindCommandLineFlag("string_flag");
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_02, "xyz", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_string_flag), "xyz");
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_02, "", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_string_flag), "");
-}
-
-// --------------------------------------------------------------------
-
-TEST_F(CommandLineFlagTest, TestParseFromDefaultValue) {
-  std::string err;
-
-  auto* flag_01 = flags::FindCommandLineFlag("int_flag");
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "111", flags::SET_FLAGS_DEFAULT, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(flag_01->DefaultValue(), "111");
-
-  auto* flag_02 = flags::FindCommandLineFlag("string_flag");
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_02, "abc", flags::SET_FLAGS_DEFAULT, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(flag_02->DefaultValue(), "abc");
-}
-
-// --------------------------------------------------------------------
-
-TEST_F(CommandLineFlagTest, TestParseFromIfDefault) {
-  std::string err;
-
-  auto* flag_01 = flags::FindCommandLineFlag("int_flag");
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "22", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
-      &err))
-      << err;
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 22);
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "33", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 22);
-  // EXPECT_EQ(err, "ERROR: int_flag is already set to 22");
-
-  // Reset back to default value
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "201", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
-      &err));
-
-  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
-      flag_01, "33", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
-      &err));
-  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 201);
-  // EXPECT_EQ(err, "ERROR: int_flag is already set to 201");
-}
-
-}  // namespace
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc
index 96c026dc..35ae55fb 100644
--- a/absl/flags/internal/flag.cc
+++ b/absl/flags/internal/flag.cc
@@ -29,7 +29,6 @@
 #include "absl/base/config.h"
 #include "absl/base/const_init.h"
 #include "absl/base/optimization.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/usage_config.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index e374ecde..97ddb5f9 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -28,8 +28,8 @@
 #include "absl/base/call_once.h"
 #include "absl/base/config.h"
 #include "absl/base/thread_annotations.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/config.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/marshalling.h"
 #include "absl/memory/memory.h"
@@ -168,6 +168,28 @@ inline const std::type_info* GenRuntimeTypeId() {
 // cases.
 using HelpGenFunc = std::string (*)();
 
+template <size_t N>
+struct FixedCharArray {
+  char value[N];
+
+  template <size_t... I>
+  static constexpr FixedCharArray<N> FromLiteralString(
+      absl::string_view str, absl::index_sequence<I...>) {
+    return (void)str, FixedCharArray<N>({{str[I]..., '\0'}});
+  }
+};
+
+template <typename Gen, size_t N = Gen::Value().size()>
+constexpr FixedCharArray<N + 1> HelpStringAsArray(int) {
+  return FixedCharArray<N + 1>::FromLiteralString(
+      Gen::Value(), absl::make_index_sequence<N>{});
+}
+
+template <typename Gen>
+constexpr std::false_type HelpStringAsArray(char) {
+  return std::false_type{};
+}
+
 union FlagHelpMsg {
   constexpr explicit FlagHelpMsg(const char* help_msg) : literal(help_msg) {}
   constexpr explicit FlagHelpMsg(HelpGenFunc help_gen) : gen_func(help_gen) {}
@@ -185,40 +207,28 @@ struct FlagHelpArg {
 
 extern const char kStrippedFlagHelp[];
 
-// HelpConstexprWrap is used by struct AbslFlagHelpGenFor##name generated by
-// ABSL_FLAG macro. It is only used to silence the compiler in the case where
-// help message expression is not constexpr and does not have type const char*.
-// If help message expression is indeed constexpr const char* HelpConstexprWrap
-// is just a trivial identity function.
-template <typename T>
-const char* HelpConstexprWrap(const T&) {
-  return nullptr;
-}
-constexpr const char* HelpConstexprWrap(const char* p) { return p; }
-constexpr const char* HelpConstexprWrap(char* p) { return p; }
-
 // These two HelpArg overloads allows us to select at compile time one of two
 // way to pass Help argument to absl::Flag. We'll be passing
-// AbslFlagHelpGenFor##name as T and integer 0 as a single argument to prefer
-// first overload if possible. If T::Const is evaluatable on constexpr
-// context (see non template int parameter below) we'll choose first overload.
-// In this case the help message expression is immediately evaluated and is used
-// to construct the absl::Flag. No additionl code is generated by ABSL_FLAG.
-// Otherwise SFINAE kicks in and first overload is dropped from the
+// AbslFlagHelpGenFor##name as Gen and integer 0 as a single argument to prefer
+// first overload if possible. If help message is evaluatable on constexpr
+// context We'll be able to make FixedCharArray out of it and we'll choose first
+// overload. In this case the help message expression is immediately evaluated
+// and is used to construct the absl::Flag. No additionl code is generated by
+// ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the
 // consideration, in which case the second overload will be used. The second
 // overload does not attempt to evaluate the help message expression
 // immediately and instead delays the evaluation by returing the function
 // pointer (&T::NonConst) genering the help message when necessary. This is
 // evaluatable in constexpr context, but the cost is an extra function being
 // generated in the ABSL_FLAG code.
-template <typename T, int = (T::Const(), 1)>
-constexpr FlagHelpArg HelpArg(int) {
-  return {FlagHelpMsg(T::Const()), FlagHelpKind::kLiteral};
+template <typename Gen, size_t N>
+constexpr FlagHelpArg HelpArg(const FixedCharArray<N>& value) {
+  return {FlagHelpMsg(value.value), FlagHelpKind::kLiteral};
 }
 
-template <typename T>
-constexpr FlagHelpArg HelpArg(char) {
-  return {FlagHelpMsg(&T::NonConst), FlagHelpKind::kGenFunc};
+template <typename Gen>
+constexpr FlagHelpArg HelpArg(std::false_type) {
+  return {FlagHelpMsg(&Gen::NonConst), FlagHelpKind::kGenFunc};
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -419,7 +429,7 @@ struct DynValueDeleter {
 
 class FlagState;
 
-class FlagImpl final : public flags_internal::CommandLineFlag {
+class FlagImpl final : public CommandLineFlag {
  public:
   constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
                      FlagHelpArg help, FlagValueStorageKind value_kind,
diff --git a/absl/flags/internal/private_handle_accessor.h b/absl/flags/internal/private_handle_accessor.h
index 40591de4..07838600 100644
--- a/absl/flags/internal/private_handle_accessor.h
+++ b/absl/flags/internal/private_handle_accessor.h
@@ -16,7 +16,7 @@
 #ifndef ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
 #define ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
 
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
diff --git a/absl/flags/internal/registry.cc b/absl/flags/internal/registry.cc
index 3b941f04..70d76557 100644
--- a/absl/flags/internal/registry.cc
+++ b/absl/flags/internal/registry.cc
@@ -28,7 +28,7 @@
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/thread_annotations.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/private_handle_accessor.h"
 #include "absl/flags/usage_config.h"
 #include "absl/strings/str_cat.h"
@@ -111,6 +111,7 @@ class FlagRegistryLock {
 };
 
 void DestroyRetiredFlag(CommandLineFlag* flag);
+
 }  // namespace
 
 void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
@@ -205,7 +206,7 @@ class FlagSaverImpl {
   // It's an error to call this more than once.
   void SaveFromRegistry() {
     assert(backup_registry_.empty());  // call only once!
-    flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
+    flags_internal::ForEachFlag([&](CommandLineFlag* flag) {
       if (auto flag_state =
               flags_internal::PrivateHandleAccessor::SaveState(flag)) {
         backup_registry_.emplace_back(std::move(flag_state));
@@ -283,7 +284,7 @@ bool RegisterCommandLineFlag(CommandLineFlag* flag) {
 
 namespace {
 
-class RetiredFlagObj final : public flags_internal::CommandLineFlag {
+class RetiredFlagObj final : public CommandLineFlag {
  public:
   constexpr RetiredFlagObj(const char* name, FlagFastTypeId type_id)
       : name_(name), type_id_(type_id) {}
@@ -319,7 +320,7 @@ class RetiredFlagObj final : public flags_internal::CommandLineFlag {
   const FlagFastTypeId type_id_;
 };
 
-void DestroyRetiredFlag(flags_internal::CommandLineFlag* flag) {
+void DestroyRetiredFlag(CommandLineFlag* flag) {
   assert(flag->IsRetired());
   delete static_cast<RetiredFlagObj*>(flag);
 }
diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h
index af8ed6b9..f722fd44 100644
--- a/absl/flags/internal/registry.h
+++ b/absl/flags/internal/registry.h
@@ -30,6 +30,8 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
+class CommandLineFlag;
+
 namespace flags_internal {
 
 CommandLineFlag* FindCommandLineFlag(absl::string_view name);
diff --git a/absl/flags/internal/type_erased.cc b/absl/flags/internal/type_erased.cc
index c13fb9b0..35b0d125 100644
--- a/absl/flags/internal/type_erased.cc
+++ b/absl/flags/internal/type_erased.cc
@@ -21,7 +21,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/private_handle_accessor.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/usage_config.h"
diff --git a/absl/flags/internal/type_erased.h b/absl/flags/internal/type_erased.h
index b43a0ff7..fd9663e2 100644
--- a/absl/flags/internal/type_erased.h
+++ b/absl/flags/internal/type_erased.h
@@ -19,7 +19,7 @@
 #include <string>
 
 #include "absl/base/config.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/strings/string_view.h"
 
diff --git a/absl/flags/internal/type_erased_test.cc b/absl/flags/internal/type_erased_test.cc
index 4ce59810..bb0ff23e 100644
--- a/absl/flags/internal/type_erased_test.cc
+++ b/absl/flags/internal/type_erased_test.cc
@@ -20,7 +20,6 @@
 
 #include "gtest/gtest.h"
 #include "absl/flags/flag.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/marshalling.h"
 #include "absl/memory/memory.h"
diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index 10accc46..11664e10 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -23,8 +23,8 @@
 #include <vector>
 
 #include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/flag.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/flag.h"
 #include "absl/flags/internal/path_util.h"
 #include "absl/flags/internal/private_handle_accessor.h"
@@ -182,8 +182,7 @@ class FlagHelpPrettyPrinter {
   bool first_line_;
 };
 
-void FlagHelpHumanReadable(const flags_internal::CommandLineFlag& flag,
-                           std::ostream* out) {
+void FlagHelpHumanReadable(const CommandLineFlag& flag, std::ostream* out) {
   FlagHelpPrettyPrinter printer(80, out);  // Max line length is 80.
 
   // Flag name.
@@ -245,11 +244,10 @@ void FlagsHelpImpl(std::ostream& out, flags_internal::FlagKindFilter filter_cb,
   // This map is used to output matching flags grouped by package and file
   // name.
   std::map<std::string,
-           std::map<std::string,
-                    std::vector<const flags_internal::CommandLineFlag*>>>
+           std::map<std::string, std::vector<const CommandLineFlag*>>>
       matching_flags;
 
-  flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
+  flags_internal::ForEachFlag([&](CommandLineFlag* flag) {
     std::string flag_filename = flag->Filename();
 
     // Ignore retired flags.
@@ -303,7 +301,7 @@ void FlagsHelpImpl(std::ostream& out, flags_internal::FlagKindFilter filter_cb,
 
 // --------------------------------------------------------------------
 // Produces the help message describing specific flag.
-void FlagHelp(std::ostream& out, const flags_internal::CommandLineFlag& flag,
+void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
               HelpFormat format) {
   if (format == HelpFormat::kHumanReadable)
     flags_internal::FlagHelpHumanReadable(flag, &out);
diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h
index 6b080fd1..0c62dc4b 100644
--- a/absl/flags/internal/usage.h
+++ b/absl/flags/internal/usage.h
@@ -20,8 +20,8 @@
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/declare.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/strings/string_view.h"
 
 // --------------------------------------------------------------------
@@ -37,7 +37,7 @@ enum class HelpFormat {
 };
 
 // Outputs the help message describing specific flag.
-void FlagHelp(std::ostream& out, const flags_internal::CommandLineFlag& flag,
+void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
               HelpFormat format = HelpFormat::kHumanReadable);
 
 // Produces the help messages for all flags matching the filter. A flag matches