Update XML output to properly print special characters. Non printable characters are skipped in output. All the "whitespace-like" (including \t, \r, \n) characters printed as plain space ' '.

PiperOrigin-RevId: 538479923
Change-Id: I62dff39bb21f376d00a7b9480f8f1d31d7015e45

2 files changed, 57 insertions, 17 deletions

diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index 6a56fce9..13852e14 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -92,8 +92,16 @@ class XMLElement {
         case '>':
           out << "&gt;";
           break;
+        case '\n':
+        case '\v':
+        case '\f':
+        case '\t':
+          out << " ";
+          break;
         default:
-          out << c;
+          if (IsValidXmlCharacter(static_cast<unsigned char>(c))) {
+            out << c;
+          }
           break;
       }
     }
@@ -102,6 +110,7 @@ class XMLElement {
   }
 
  private:
+  static bool IsValidXmlCharacter(unsigned char c) { return c >= 0x20; }
   absl::string_view tag_;
   absl::string_view txt_;
 };
diff --git a/absl/flags/internal/usage_test.cc b/absl/flags/internal/usage_test.cc
index c3ab4a42..6847386f 100644
--- a/absl/flags/internal/usage_test.cc
+++ b/absl/flags/internal/usage_test.cc
@@ -39,6 +39,8 @@ ABSL_FLAG(double, usage_reporting_test_flag_03, 1.03,
           "usage_reporting_test_flag_03 help message");
 ABSL_FLAG(int64_t, usage_reporting_test_flag_04, 1000000000000004L,
           "usage_reporting_test_flag_04 help message");
+ABSL_FLAG(std::string, usage_reporting_test_flag_07, "\r\n\f\v\a\b\t ",
+          "usage_reporting_test_flag_07 help \r\n\f\v\a\b\t ");
 
 static const char kTestUsageMessage[] = "Custom usage message";
 
@@ -203,8 +205,12 @@ TEST_F(UsageReportingTest, TestFlagsHelpHRF) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -267,8 +273,9 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpshort) {
   std::stringstream test_buf;
   EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
             flags::HelpMode::kShort);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -285,8 +292,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_helpshort) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -301,8 +312,9 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_simple) {
   std::stringstream test_buf;
   EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
             flags::HelpMode::kImportant);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -319,8 +331,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_simple) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -361,8 +377,9 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_multiple_flag) {
   std::stringstream test_buf;
   EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
             flags::HelpMode::kMatch);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -379,8 +396,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_help_multiple_flag) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -395,8 +416,9 @@ TEST_F(UsageReportingTest, TestUsageFlag_helppackage) {
   std::stringstream test_buf;
   EXPECT_EQ(flags::HandleUsageFlags(test_buf, kTestUsageMessage),
             flags::HelpMode::kPackage);
-  EXPECT_EQ(test_buf.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(
+      test_buf.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -413,8 +435,12 @@ TEST_F(UsageReportingTest, TestUsageFlag_helppackage) {
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
 
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
+
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.
@@ -471,8 +497,9 @@ path.
   std::stringstream test_buf_02;
   EXPECT_EQ(flags::HandleUsageFlags(test_buf_02, kTestUsageMessage),
             flags::HelpMode::kMatch);
-  EXPECT_EQ(test_buf_02.str(),
-            R"(usage_test: Custom usage message
+  EXPECT_EQ(
+      test_buf_02.str(),
+      R"(usage_test: Custom usage message
 
   Flags from absl/flags/internal/usage_test.cc:
     --usage_reporting_test_flag_01 (usage_reporting_test_flag_01 help message);
@@ -489,8 +516,12 @@ path.
 
       Some more help.
       Even more long long long long long long long long long long long long help
-      message.); default: "";
+      message.); default: "";)"
+
+      "\n    --usage_reporting_test_flag_07 (usage_reporting_test_flag_07 "
+      "help\n\n      \f\v\a\b ); default: \"\r\n\f\v\a\b\t \";\n"
 
+      R"(
 Try --helpfull to get a list of all flags or --help=substring shows help for
 flags which include specified substring in either in the name, or description or
 path.