Change ParseAbseilFlagsOnly function to include handling of usage flags and exit on syntax errors.

PiperOrigin-RevId: 518198160
Change-Id: Ib4fe53e0b0b371472b6b9473aeb84779953b6a38

4 files changed, 72 insertions, 45 deletions

diff --git a/absl/flags/internal/parse.h b/absl/flags/internal/parse.h
index 145e591d..e4352049 100644
--- a/absl/flags/internal/parse.h
+++ b/absl/flags/internal/parse.h
@@ -21,6 +21,7 @@
 
 #include "absl/base/config.h"
 #include "absl/flags/declare.h"
+#include "absl/flags/internal/usage.h"
 #include "absl/strings/string_view.h"
 
 ABSL_DECLARE_FLAG(std::vector<std::string>, flagfile);
@@ -40,8 +41,8 @@ enum class OnUndefinedFlag {
 };
 
 std::vector<char*> ParseCommandLineImpl(int argc, char* argv[],
-                                        UsageFlagsAction usage_flag_act,
-                                        OnUndefinedFlag on_undef_flag);
+                                        UsageFlagsAction usage_flag_action,
+                                        OnUndefinedFlag undef_flag_action);
 
 // --------------------------------------------------------------------
 // Inspect original command line
diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index e9481488..6a56fce9 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -18,6 +18,7 @@
 #include <stdint.h>
 
 #include <algorithm>
+#include <cstdlib>
 #include <functional>
 #include <iterator>
 #include <map>
@@ -354,8 +355,8 @@ void FlagsHelp(std::ostream& out, absl::string_view filter, HelpFormat format,
 // --------------------------------------------------------------------
 // Checks all the 'usage' command line flags to see if any have been set.
 // If so, handles them appropriately.
-int HandleUsageFlags(std::ostream& out,
-                     absl::string_view program_usage_message) {
+HelpMode HandleUsageFlags(std::ostream& out,
+                          absl::string_view program_usage_message) {
   switch (GetFlagsHelpMode()) {
     case HelpMode::kNone:
       break;
@@ -363,25 +364,24 @@ int HandleUsageFlags(std::ostream& out,
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_help_flags,
           GetFlagsHelpFormat(), program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kShort:
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_helpshort_flags,
           GetFlagsHelpFormat(), program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kFull:
       flags_internal::FlagsHelp(out, "", GetFlagsHelpFormat(),
                                 program_usage_message);
-      return 1;
+      break;
 
     case HelpMode::kPackage:
       flags_internal::FlagsHelpImpl(
           out, flags_internal::GetUsageConfig().contains_helppackage_flags,
           GetFlagsHelpFormat(), program_usage_message);
-
-      return 1;
+      break;
 
     case HelpMode::kMatch: {
       std::string substr = GetFlagsHelpMatchSubstr();
@@ -400,20 +400,19 @@ int HandleUsageFlags(std::ostream& out,
         flags_internal::FlagsHelpImpl(
             out, filter_cb, HelpFormat::kHumanReadable, program_usage_message);
       }
-
-      return 1;
+      break;
     }
     case HelpMode::kVersion:
       if (flags_internal::GetUsageConfig().version_string)
         out << flags_internal::GetUsageConfig().version_string();
       // Unlike help, we may be asking for version in a script, so return 0
-      return 0;
+      break;
 
     case HelpMode::kOnlyCheckArgs:
-      return 0;
+      break;
   }
 
-  return -1;
+  return GetFlagsHelpMode();
 }
 
 // --------------------------------------------------------------------
@@ -521,6 +520,22 @@ bool DeduceUsageFlags(absl::string_view name, absl::string_view value) {
   return false;
 }
 
+// --------------------------------------------------------------------
+
+void MaybeExit(HelpMode mode) {
+  switch (mode) {
+    case flags_internal::HelpMode::kNone:
+      return;
+    case flags_internal::HelpMode::kOnlyCheckArgs:
+    case flags_internal::HelpMode::kVersion:
+      std::exit(0);
+    default:  // For all the other modes we exit with 1
+      std::exit(1);
+  }
+}
+
+// --------------------------------------------------------------------
+
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h
index c0bcac57..a96cbf38 100644
--- a/absl/flags/internal/usage.h
+++ b/absl/flags/internal/usage.h
@@ -17,11 +17,11 @@
 #define ABSL_FLAGS_INTERNAL_USAGE_H_
 
 #include <iosfwd>
+#include <ostream>
 #include <string>
 
 #include "absl/base/config.h"
 #include "absl/flags/commandlineflag.h"
-#include "absl/flags/declare.h"
 #include "absl/strings/string_view.h"
 
 // --------------------------------------------------------------------
@@ -36,6 +36,18 @@ enum class HelpFormat {
   kHumanReadable,
 };
 
+// The kind of usage help requested.
+enum class HelpMode {
+  kNone,
+  kImportant,
+  kShort,
+  kFull,
+  kPackage,
+  kMatch,
+  kVersion,
+  kOnlyCheckArgs
+};
+
 // Streams the help message describing `flag` to `out`.
 // The default value for `flag` is included in the output.
 void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
@@ -57,28 +69,18 @@ void FlagsHelp(std::ostream& out, absl::string_view filter,
 
 // If any of the 'usage' related command line flags (listed on the bottom of
 // this file) has been set this routine produces corresponding help message in
-// the specified output stream and returns:
-//  0 - if "version" or "only_check_flags" flags were set and handled.
-//  1 - if some other 'usage' related flag was set and handled.
-// -1 - if no usage flags were set on a commmand line.
-// Non negative return values are expected to be used as an exit code for a
-// binary.
-int HandleUsageFlags(std::ostream& out,
-                     absl::string_view program_usage_message);
+// the specified output stream and returns HelpMode that was handled. Otherwise
+// it returns HelpMode::kNone.
+HelpMode HandleUsageFlags(std::ostream& out,
+                          absl::string_view program_usage_message);
 
 // --------------------------------------------------------------------
-// Globals representing usage reporting flags
+// Encapsulates the logic of exiting the binary depending on handled help mode.
 
-enum class HelpMode {
-  kNone,
-  kImportant,
-  kShort,
-  kFull,
-  kPackage,
-  kMatch,
-  kVersion,
-  kOnlyCheckArgs
-};
+void MaybeExit(HelpMode mode);
+
+// --------------------------------------------------------------------
+// Globals representing usage reporting flags
 
 // Returns substring to filter help output (--help=substr argument)
 std::string GetFlagsHelpMatchSubstr();
diff --git a/absl/flags/internal/usage_test.cc b/absl/flags/internal/usage_test.cc
index 209a7be9..c3ab4a42 100644
--- a/absl/flags/internal/usage_test.cc
+++ b/absl/flags/internal/usage_test.cc
@@ -24,7 +24,6 @@
 #include "gtest/gtest.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/internal/parse.h"
-#include "absl/flags/internal/path_util.h"
 #include "absl/flags/internal/program_name.h"
 #include "absl/flags/reflection.h"
 #include "absl/flags/usage.h"
@@ -256,7 +255,8 @@ path.
 
 TEST_F(UsageReportingTest, TestNoUsageFlags) {
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), -1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kNone);
 }
 
 // --------------------------------------------------------------------
@@ -265,7 +265,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpshort) {
   flags::SetFlagsHelpMode(flags::HelpMode::kShort);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kShort);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -298,7 +299,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_simple) {
   flags::SetFlagsHelpMode(flags::HelpMode::kImportant);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kImportant);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -332,7 +334,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_one_flag) {
   flags::SetFlagsHelpMatchSubstr("usage_reporting_test_flag_06");
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -356,7 +359,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_multiple_flag) {
   flags::SetFlagsHelpMatchSubstr("test_flag");
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -389,7 +393,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_helppackage) {
   flags::SetFlagsHelpMode(flags::HelpMode::kPackage);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kPackage);
   EXPECT_EQ(test_buf.str(),
             R"(usage_test: Custom usage message
 
@@ -422,7 +427,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_version) {
   flags::SetFlagsHelpMode(flags::HelpMode::kVersion);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 0);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kVersion);
 #ifndef NDEBUG
   EXPECT_EQ(test_buf.str(), "usage_test\nDebug build (NDEBUG not #defined)\n");
 #else
@@ -436,7 +442,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_only_check_args) {
   flags::SetFlagsHelpMode(flags::HelpMode::kOnlyCheckArgs);
 
   std::stringstream test_buf;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage), 0);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
+            flags::HelpMode::kOnlyCheckArgs);
   EXPECT_EQ(test_buf.str(), "");
 }
 
@@ -447,7 +454,8 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpon) {
   flags::SetFlagsHelpMatchSubstr("/bla-bla.");
 
   std::stringstream test_buf_01;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf_01, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf_01, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf_01.str(),
             R"(usage_test: Custom usage message
 
@@ -461,7 +469,8 @@ path.
   flags::SetFlagsHelpMatchSubstr("/usage_test.");
 
   std::stringstream test_buf_02;
-  EXPECT_EQ(flags::HandleUsageFlags(test_buf_02, kTestUsageMessage), 1);
+  EXPECT_EQ(flags::HandleUsageFlags(test_buf_02, kTestUsageMessage),
+            flags::HelpMode::kMatch);
   EXPECT_EQ(test_buf_02.str(),
             R"(usage_test: Custom usage message